Publisher: Elsevier   (Total: 3161 journals)

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Showing 1 - 200 of 3161 Journals sorted alphabetically
Academic Pediatrics     Hybrid Journal   (Followers: 39, SJR: 1.655, CiteScore: 2)
Academic Radiology     Hybrid Journal   (Followers: 26, SJR: 1.015, CiteScore: 2)
Accident Analysis & Prevention     Partially Free   (Followers: 106, SJR: 1.462, CiteScore: 3)
Accounting Forum     Hybrid Journal   (Followers: 28, SJR: 0.932, CiteScore: 2)
Accounting, Organizations and Society     Hybrid Journal   (Followers: 44, SJR: 1.771, CiteScore: 3)
Achievements in the Life Sciences     Open Access   (Followers: 7)
Acta Anaesthesiologica Taiwanica     Open Access   (Followers: 6)
Acta Astronautica     Hybrid Journal   (Followers: 446, SJR: 0.758, CiteScore: 2)
Acta Automatica Sinica     Full-text available via subscription   (Followers: 2)
Acta Biomaterialia     Hybrid Journal   (Followers: 30, SJR: 1.967, CiteScore: 7)
Acta Colombiana de Cuidado Intensivo     Full-text available via subscription   (Followers: 3)
Acta de Investigación Psicológica     Open Access   (Followers: 2)
Acta Ecologica Sinica     Open Access   (Followers: 12, SJR: 0.18, CiteScore: 1)
Acta Histochemica     Hybrid Journal   (Followers: 5, SJR: 0.661, CiteScore: 2)
Acta Materialia     Hybrid Journal   (Followers: 324, SJR: 3.263, CiteScore: 6)
Acta Mathematica Scientia     Full-text available via subscription   (Followers: 5, SJR: 0.504, CiteScore: 1)
Acta Mechanica Solida Sinica     Full-text available via subscription   (Followers: 9, SJR: 0.542, CiteScore: 1)
Acta Oecologica     Hybrid Journal   (Followers: 12, SJR: 0.834, CiteScore: 2)
Acta Otorrinolaringologica (English Edition)     Full-text available via subscription  
Acta Otorrinolaringológica Española     Full-text available via subscription   (Followers: 2, SJR: 0.307, CiteScore: 0)
Acta Pharmaceutica Sinica B     Open Access   (Followers: 2, SJR: 1.793, CiteScore: 6)
Acta Psychologica     Hybrid Journal   (Followers: 26, SJR: 1.331, CiteScore: 2)
Acta Sociológica     Open Access   (Followers: 1)
Acta Tropica     Hybrid Journal   (Followers: 6, SJR: 1.052, CiteScore: 2)
Acta Urológica Portuguesa     Open Access   (Followers: 1)
Actas Dermo-Sifiliograficas     Full-text available via subscription   (Followers: 3, SJR: 0.374, CiteScore: 1)
Actas Dermo-Sifiliográficas (English Edition)     Full-text available via subscription   (Followers: 2)
Actas Urológicas Españolas     Full-text available via subscription   (Followers: 3, SJR: 0.344, CiteScore: 1)
Actas Urológicas Españolas (English Edition)     Full-text available via subscription   (Followers: 1)
Actualites Pharmaceutiques     Full-text available via subscription   (Followers: 7, SJR: 0.19, CiteScore: 0)
Actualites Pharmaceutiques Hospitalieres     Full-text available via subscription   (Followers: 3)
Acupuncture and Related Therapies     Hybrid Journal   (Followers: 8)
Acute Pain     Full-text available via subscription   (Followers: 15, SJR: 2.671, CiteScore: 5)
Ad Hoc Networks     Hybrid Journal   (Followers: 11, SJR: 0.53, CiteScore: 4)
Addictive Behaviors     Hybrid Journal   (Followers: 18, SJR: 1.29, CiteScore: 3)
Addictive Behaviors Reports     Open Access   (Followers: 9, SJR: 0.755, CiteScore: 2)
Additive Manufacturing     Hybrid Journal   (Followers: 13, SJR: 2.611, CiteScore: 8)
Additives for Polymers     Full-text available via subscription   (Followers: 22)
Advanced Drug Delivery Reviews     Hybrid Journal   (Followers: 189, SJR: 4.09, CiteScore: 13)
Advanced Engineering Informatics     Hybrid Journal   (Followers: 13, SJR: 1.167, CiteScore: 4)
Advanced Powder Technology     Hybrid Journal   (Followers: 17, SJR: 0.694, CiteScore: 3)
Advances in Accounting     Hybrid Journal   (Followers: 9, SJR: 0.277, CiteScore: 1)
Advances in Agronomy     Full-text available via subscription   (Followers: 17, SJR: 2.384, CiteScore: 5)
Advances in Anesthesia     Full-text available via subscription   (Followers: 30, SJR: 0.126, CiteScore: 0)
Advances in Antiviral Drug Design     Full-text available via subscription   (Followers: 2)
Advances in Applied Mathematics     Full-text available via subscription   (Followers: 12, SJR: 0.992, CiteScore: 1)
Advances in Applied Mechanics     Full-text available via subscription   (Followers: 12, SJR: 1.551, CiteScore: 4)
Advances in Applied Microbiology     Full-text available via subscription   (Followers: 24, SJR: 2.089, CiteScore: 5)
Advances In Atomic, Molecular, and Optical Physics     Full-text available via subscription   (Followers: 15, SJR: 0.572, CiteScore: 2)
Advances in Biological Regulation     Hybrid Journal   (Followers: 4, SJR: 2.61, CiteScore: 7)
Advances in Botanical Research     Full-text available via subscription   (Followers: 1, SJR: 0.686, CiteScore: 2)
Advances in Cancer Research     Full-text available via subscription   (Followers: 35, SJR: 3.043, CiteScore: 6)
Advances in Carbohydrate Chemistry and Biochemistry     Full-text available via subscription   (Followers: 9, SJR: 1.453, CiteScore: 2)
Advances in Catalysis     Full-text available via subscription   (Followers: 5, SJR: 1.992, CiteScore: 5)
Advances in Cell Aging and Gerontology     Full-text available via subscription   (Followers: 5)
Advances in Cellular and Molecular Biology of Membranes and Organelles     Full-text available via subscription   (Followers: 14)
Advances in Chemical Engineering     Full-text available via subscription   (Followers: 29, SJR: 0.156, CiteScore: 1)
Advances in Child Development and Behavior     Full-text available via subscription   (Followers: 11, SJR: 0.713, CiteScore: 1)
Advances in Chronic Kidney Disease     Full-text available via subscription   (Followers: 11, SJR: 1.316, CiteScore: 2)
Advances in Clinical Chemistry     Full-text available via subscription   (Followers: 26, SJR: 1.562, CiteScore: 3)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 21, SJR: 1.977, CiteScore: 8)
Advances in Computers     Full-text available via subscription   (Followers: 14, SJR: 0.205, CiteScore: 1)
Advances in Dermatology     Full-text available via subscription   (Followers: 16)
Advances in Developmental Biology     Full-text available via subscription   (Followers: 14)
Advances in Digestive Medicine     Open Access   (Followers: 13)
Advances in DNA Sequence-Specific Agents     Full-text available via subscription   (Followers: 7)
Advances in Drug Research     Full-text available via subscription   (Followers: 26)
Advances in Ecological Research     Full-text available via subscription   (Followers: 45, SJR: 2.524, CiteScore: 4)
Advances in Engineering Software     Hybrid Journal   (Followers: 30, SJR: 1.159, CiteScore: 4)
Advances in Experimental Biology     Full-text available via subscription   (Followers: 9)
Advances in Experimental Social Psychology     Full-text available via subscription   (Followers: 52, SJR: 5.39, CiteScore: 8)
Advances in Exploration Geophysics     Full-text available via subscription   (Followers: 2)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 9)
Advances in Food and Nutrition Research     Full-text available via subscription   (Followers: 68, SJR: 0.591, CiteScore: 2)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 17)
Advances in Genetics     Full-text available via subscription   (Followers: 21, SJR: 1.354, CiteScore: 4)
Advances in Genome Biology     Full-text available via subscription   (Followers: 12, SJR: 12.74, CiteScore: 13)
Advances in Geophysics     Full-text available via subscription   (Followers: 8, SJR: 1.193, CiteScore: 3)
Advances in Heat Transfer     Full-text available via subscription   (Followers: 26, SJR: 0.368, CiteScore: 1)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 11, SJR: 0.749, CiteScore: 3)
Advances in Human Factors/Ergonomics     Full-text available via subscription   (Followers: 26)
Advances in Imaging and Electron Physics     Full-text available via subscription   (Followers: 3, SJR: 0.193, CiteScore: 0)
Advances in Immunology     Full-text available via subscription   (Followers: 37, SJR: 4.433, CiteScore: 6)
Advances in Inorganic Chemistry     Full-text available via subscription   (Followers: 10, SJR: 1.163, CiteScore: 2)
Advances in Insect Physiology     Full-text available via subscription   (Followers: 2, SJR: 1.938, CiteScore: 3)
Advances in Integrative Medicine     Hybrid Journal   (Followers: 6, SJR: 0.176, CiteScore: 0)
Advances in Intl. Accounting     Full-text available via subscription   (Followers: 3)
Advances in Life Course Research     Hybrid Journal   (Followers: 9, SJR: 0.682, CiteScore: 2)
Advances in Lipobiology     Full-text available via subscription   (Followers: 1)
Advances in Magnetic and Optical Resonance     Full-text available via subscription   (Followers: 8)
Advances in Marine Biology     Full-text available via subscription   (Followers: 21, SJR: 0.88, CiteScore: 2)
Advances in Mathematics     Full-text available via subscription   (Followers: 17, SJR: 3.027, CiteScore: 2)
Advances in Medical Sciences     Hybrid Journal   (Followers: 9, SJR: 0.694, CiteScore: 2)
Advances in Medicinal Chemistry     Full-text available via subscription   (Followers: 6)
Advances in Microbial Physiology     Full-text available via subscription   (Followers: 5, SJR: 1.158, CiteScore: 3)
Advances in Molecular and Cell Biology     Full-text available via subscription   (Followers: 26)
Advances in Molecular and Cellular Endocrinology     Full-text available via subscription   (Followers: 8)
Advances in Molecular Toxicology     Full-text available via subscription   (Followers: 7, SJR: 0.182, CiteScore: 0)
Advances in Nanoporous Materials     Full-text available via subscription   (Followers: 5)
Advances in Oncobiology     Full-text available via subscription   (Followers: 2)
Advances in Organ Biology     Full-text available via subscription   (Followers: 2)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 18, SJR: 1.875, CiteScore: 4)
Advances in Parallel Computing     Full-text available via subscription   (Followers: 7, SJR: 0.174, CiteScore: 0)
Advances in Parasitology     Full-text available via subscription   (Followers: 6, SJR: 1.579, CiteScore: 4)
Advances in Pediatrics     Full-text available via subscription   (Followers: 27, SJR: 0.461, CiteScore: 1)
Advances in Pharmaceutical Sciences     Full-text available via subscription   (Followers: 19)
Advances in Pharmacology     Full-text available via subscription   (Followers: 17, SJR: 1.536, CiteScore: 3)
Advances in Physical Organic Chemistry     Full-text available via subscription   (Followers: 10, SJR: 0.574, CiteScore: 1)
Advances in Phytomedicine     Full-text available via subscription  
Advances in Planar Lipid Bilayers and Liposomes     Full-text available via subscription   (Followers: 3, SJR: 0.109, CiteScore: 1)
Advances in Plant Biochemistry and Molecular Biology     Full-text available via subscription   (Followers: 11)
Advances in Plant Pathology     Full-text available via subscription   (Followers: 6)
Advances in Porous Media     Full-text available via subscription   (Followers: 5)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 19)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 20, SJR: 0.791, CiteScore: 2)
Advances in Psychology     Full-text available via subscription   (Followers: 69)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 7, SJR: 0.371, CiteScore: 1)
Advances in Radiation Oncology     Open Access   (Followers: 3, SJR: 0.263, CiteScore: 1)
Advances in Small Animal Medicine and Surgery     Hybrid Journal   (Followers: 3, SJR: 0.101, CiteScore: 0)
Advances in Space Biology and Medicine     Full-text available via subscription   (Followers: 7)
Advances in Space Research     Full-text available via subscription   (Followers: 429, SJR: 0.569, CiteScore: 2)
Advances in Structural Biology     Full-text available via subscription   (Followers: 6)
Advances in Surgery     Full-text available via subscription   (Followers: 13, SJR: 0.555, CiteScore: 2)
Advances in the Study of Behavior     Full-text available via subscription   (Followers: 37, SJR: 2.208, CiteScore: 4)
Advances in Veterinary Medicine     Full-text available via subscription   (Followers: 20)
Advances in Veterinary Science and Comparative Medicine     Full-text available via subscription   (Followers: 15)
Advances in Virus Research     Full-text available via subscription   (Followers: 6, SJR: 2.262, CiteScore: 5)
Advances in Water Resources     Hybrid Journal   (Followers: 57, SJR: 1.551, CiteScore: 3)
Aeolian Research     Hybrid Journal   (Followers: 6, SJR: 1.117, CiteScore: 3)
Aerospace Science and Technology     Hybrid Journal   (Followers: 395, SJR: 0.796, CiteScore: 3)
AEU - Intl. J. of Electronics and Communications     Hybrid Journal   (Followers: 8, SJR: 0.42, CiteScore: 2)
African J. of Emergency Medicine     Open Access   (Followers: 6, SJR: 0.296, CiteScore: 0)
Ageing Research Reviews     Hybrid Journal   (Followers: 12, SJR: 3.671, CiteScore: 9)
Aggression and Violent Behavior     Hybrid Journal   (Followers: 487, SJR: 1.238, CiteScore: 3)
Agri Gene     Hybrid Journal   (Followers: 1, SJR: 0.13, CiteScore: 0)
Agricultural and Forest Meteorology     Hybrid Journal   (Followers: 18, SJR: 1.818, CiteScore: 5)
Agricultural Systems     Hybrid Journal   (Followers: 32, SJR: 1.156, CiteScore: 4)
Agricultural Water Management     Hybrid Journal   (Followers: 47, SJR: 1.272, CiteScore: 3)
Agriculture and Agricultural Science Procedia     Open Access   (Followers: 4)
Agriculture and Natural Resources     Open Access   (Followers: 3)
Agriculture, Ecosystems & Environment     Hybrid Journal   (Followers: 58, SJR: 1.747, CiteScore: 4)
Ain Shams Engineering J.     Open Access   (Followers: 5, SJR: 0.589, CiteScore: 3)
Air Medical J.     Hybrid Journal   (Followers: 8, SJR: 0.26, CiteScore: 0)
AKCE Intl. J. of Graphs and Combinatorics     Open Access   (SJR: 0.19, CiteScore: 0)
Alcohol     Hybrid Journal   (Followers: 12, SJR: 1.153, CiteScore: 3)
Alcoholism and Drug Addiction     Open Access   (Followers: 12)
Alergologia Polska : Polish J. of Allergology     Full-text available via subscription   (Followers: 1)
Alexandria Engineering J.     Open Access   (Followers: 2, SJR: 0.604, CiteScore: 3)
Alexandria J. of Medicine     Open Access   (Followers: 1, SJR: 0.191, CiteScore: 1)
Algal Research     Partially Free   (Followers: 11, SJR: 1.142, CiteScore: 4)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 2)
Allergologia et Immunopathologia     Full-text available via subscription   (Followers: 1, SJR: 0.504, CiteScore: 1)
Allergology Intl.     Open Access   (Followers: 5, SJR: 1.148, CiteScore: 2)
Alpha Omegan     Full-text available via subscription   (SJR: 3.521, CiteScore: 6)
ALTER - European J. of Disability Research / Revue Européenne de Recherche sur le Handicap     Full-text available via subscription   (Followers: 11, SJR: 0.201, CiteScore: 1)
Alzheimer's & Dementia     Hybrid Journal   (Followers: 55, SJR: 4.66, CiteScore: 10)
Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring     Open Access   (Followers: 6, SJR: 1.796, CiteScore: 4)
Alzheimer's & Dementia: Translational Research & Clinical Interventions     Open Access   (Followers: 6, SJR: 1.108, CiteScore: 3)
Ambulatory Pediatrics     Hybrid Journal   (Followers: 5)
American Heart J.     Hybrid Journal   (Followers: 58, SJR: 3.267, CiteScore: 4)
American J. of Cardiology     Hybrid Journal   (Followers: 67, SJR: 1.93, CiteScore: 3)
American J. of Emergency Medicine     Hybrid Journal   (Followers: 48, SJR: 0.604, CiteScore: 1)
American J. of Geriatric Pharmacotherapy     Full-text available via subscription   (Followers: 13)
American J. of Geriatric Psychiatry     Hybrid Journal   (Followers: 15, SJR: 1.524, CiteScore: 3)
American J. of Human Genetics     Hybrid Journal   (Followers: 40, SJR: 7.45, CiteScore: 8)
American J. of Infection Control     Hybrid Journal   (Followers: 29, SJR: 1.062, CiteScore: 2)
American J. of Kidney Diseases     Hybrid Journal   (Followers: 37, SJR: 2.973, CiteScore: 4)
American J. of Medicine     Hybrid Journal   (Followers: 50)
American J. of Medicine Supplements     Full-text available via subscription   (Followers: 3, SJR: 1.967, CiteScore: 2)
American J. of Obstetrics and Gynecology     Hybrid Journal   (Followers: 265, SJR: 2.7, CiteScore: 4)
American J. of Ophthalmology     Hybrid Journal   (Followers: 67, SJR: 3.184, CiteScore: 4)
American J. of Ophthalmology Case Reports     Open Access   (Followers: 5, SJR: 0.265, CiteScore: 0)
American J. of Orthodontics and Dentofacial Orthopedics     Full-text available via subscription   (Followers: 6, SJR: 1.289, CiteScore: 1)
American J. of Otolaryngology     Hybrid Journal   (Followers: 25, SJR: 0.59, CiteScore: 1)
American J. of Pathology     Hybrid Journal   (Followers: 32, SJR: 2.139, CiteScore: 4)
American J. of Preventive Medicine     Hybrid Journal   (Followers: 30, SJR: 2.164, CiteScore: 4)
American J. of Surgery     Hybrid Journal   (Followers: 39, SJR: 1.141, CiteScore: 2)
American J. of the Medical Sciences     Hybrid Journal   (Followers: 12, SJR: 0.767, CiteScore: 1)
Ampersand : An Intl. J. of General and Applied Linguistics     Open Access   (Followers: 7)
Anaerobe     Hybrid Journal   (Followers: 4, SJR: 1.144, CiteScore: 3)
Anaesthesia & Intensive Care Medicine     Full-text available via subscription   (Followers: 67, SJR: 0.138, CiteScore: 0)
Anaesthesia Critical Care & Pain Medicine     Full-text available via subscription   (Followers: 25, SJR: 0.411, CiteScore: 1)
Anales de Cirugia Vascular     Full-text available via subscription   (Followers: 1)
Anales de Pediatría     Full-text available via subscription   (Followers: 3, SJR: 0.277, CiteScore: 0)
Anales de Pediatría (English Edition)     Full-text available via subscription  
Anales de Pediatría Continuada     Full-text available via subscription  
Analytic Methods in Accident Research     Hybrid Journal   (Followers: 6, SJR: 4.849, CiteScore: 10)
Analytica Chimica Acta     Hybrid Journal   (Followers: 44, SJR: 1.512, CiteScore: 5)
Analytica Chimica Acta : X     Open Access  
Analytical Biochemistry     Hybrid Journal   (Followers: 213, SJR: 0.633, CiteScore: 2)
Analytical Chemistry Research     Open Access   (Followers: 13, SJR: 0.411, CiteScore: 2)
Analytical Spectroscopy Library     Full-text available via subscription   (Followers: 14)
Anesthésie & Réanimation     Full-text available via subscription   (Followers: 2)
Anesthesiology Clinics     Full-text available via subscription   (Followers: 25, SJR: 0.683, CiteScore: 2)
Angiología     Full-text available via subscription   (SJR: 0.121, CiteScore: 0)
Angiologia e Cirurgia Vascular     Open Access   (Followers: 1, SJR: 0.111, CiteScore: 0)
Animal Behaviour     Hybrid Journal   (Followers: 237, SJR: 1.58, CiteScore: 3)
Animal Feed Science and Technology     Hybrid Journal   (Followers: 7, SJR: 0.937, CiteScore: 2)
Animal Reproduction Science     Hybrid Journal   (Followers: 7, SJR: 0.704, CiteScore: 2)
Annales d'Endocrinologie     Full-text available via subscription   (Followers: 3, SJR: 0.451, CiteScore: 1)

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Similar Journals
Journal Cover
Algal Research
Journal Prestige (SJR): 1.142
Citation Impact (citeScore): 4
Number of Followers: 11  
 
  Partially Free Journal Partially Free Journal
ISSN (Online) 2211-9264
Published by Elsevier Homepage  [3161 journals]
  • Chemotyping of terrestrial Nostoc-like isolates from alkali grassland
           areas by non-targeted peptide analysis
    • Abstract: Publication date: March 2020Source: Algal Research, Volume 46Author(s): Milán Riba, Attila Kiss-Szikszai, Sándor Gonda, Péter Parizsa, Balázs Deák, Péter Török, Orsolya Valkó, Tamás Felföldi, Gábor VasasAbstractThe Nostoc genus is a well-known heterocytous, filamentous cyanobacterium which can be found all over the world. The size of terrestrial and/or freshwater colonies can be microscopic and macroscopic as well. In addition, Nostoc species are one of the most common photosynthetic cyanobacterial partners in symbiotic interactions. Terrestrial cyanobacterial colonies were collected and isolated in this study from various alkali grassland habitats (Great Hungarian Plain). Altogether 133 colonies were isolated from the 65 collected samples. The peptide patterns of the Nostoc-like strains were examined using HPLC-ESI-MS/MS and 41 peptides were identified from 45 isolated Nostoc-like strains; these compounds belonged to 4 different peptide classes. Twelve nostoginin/microginin, 16 anabaenopeptin, 12 banyaside/suomilide variants were identified. 37% of our isolated Nostoc-like strains produced some of the peptide metabolites we tested. These strains showed distinct chemotypes according to their peptide patterns, and can be divided into 4 groups based on their metabolisms. Strains either contained: (1) nostoginins/microginins, (2) anabaenopeptins, (3) anabaenopeptins and banyasides or (4) banyasides as major compounds. Banyasides were present in many of our strains and showed very high intensity in some cases. A number of previously unknown banyaside variants have been identified.
       
  • Role of surface roughness in the algal short-term cell adhesion and
           long-term biofilm cultivation under dynamic flow condition
    • Abstract: Publication date: March 2020Source: Algal Research, Volume 46Author(s): Qi Zhang, Zhigang Yu, Shiping Jin, Cuixia Liu, Yubiao Li, Dabin Guo, Mian Hu, Roger Ruan, Yuhuan LiuSurface roughness can enhance the deposition of algal cells to carrier surface and improve the production of algal biofilm. However, the corresponding underlying mechanisms remain unclear. In this study, pine sawdust, sugar bagasse, rice husk, elastic filler and quartz sand were selected as carriers and their surface roughness were measured using a confocal laser-scanning microscopy. Cell transportation experiments and long-term biofilm cultivation on these carriers were conducted in a self-designed thirty-channel algal biofilm reactor under dynamic flow condition. Results indicated that pine sawdust (0.420 to 0.595 mm, root-mean-square roughness Sq = 45.16 μm) was more suitable, efficient and cost-saving carrier for algal biofilm cultivation under the developed “regrowth mode” (using the residual suspended algal cells from the previous culture cycle as inoculum), with the productivity of algal biofilm achieved 14.75–15.75 g·m−2·day−1 after 8 days cultivation. Increase of carrier surface roughness (Sq: from 13.03 to 45.15 μm) enhanced the short-term (1 day) cell adhesion to surface (from 6.89 to 23.92 g·m−2·day−1). The productivity of the long-term (8 days) cultivated biofilm positively correlated with the rate of short-term cell adhesion and carrier surface roughness. Computational fluid dynamics (CFD) analysis revealed that these positive correlations were due to the created local hydrodynamic conditions by surface roughness. More asperities and hydrodynamic stagnant zones on the rougher surface promoted the interception and retention of algal cells and enhanced the cell adhesion strength, and further contributed to the intensive inoculation as well as the formation of robust and strengthened biofilm, thus finally leading to the improved biomass production indirectly. Findings of the present study are of particular importance for the manufacture of man-made rough carriers, the inoculation of biofilm systems and the enhancement of biomass productivity during the large-scale algal biofilm cultivation process.Graphical abstractUnlabelled Image
       
  • Dynamic changes in community composition of Scenedesmus-seeded artificial,
           engineered microalgal biofilms
    • Abstract: Publication date: March 2020Source: Algal Research, Volume 46Author(s): Alexandre J. Paquette, Christine E. Sharp, Peter J. Schnurr, D. Grant Allen, Steven M. Short, George S. EspieAbstractArtificial, non-sterile, microalgal biofilms present a promising biotechnological avenue for the production of valuable biomass, biofuels and biochemicals while simultaneously engaging in photosynthetic carbon capture. Here we use a psbA amplicon library and high-throughput 16S and 18S rRNA gene sequencing to investigate the effects of time and CO2 concentration on the composition and community dynamics of photoautotrophically grown microalgal biofilms pre-conditioned with wastewater and heavily seeded with the green alga Scenedesmus obliquus. While biomass increased in a stable, linear manner, our analysis revealed that the photoautotrophic community dramatically changed over time. Photoautotrophs such as Chorella and the cyanobacterium Leptolyngbya, presumably seeded from the wastewater, rapidly established as constituents of the biofilm while the seed species was far less dominant than anticipated. With time, photoautotrophic diatoms and dinoflagellates also established themselves as constituents of the biofilm. Low CO2 (0.04% v/v) favoured the early proliferation of cyanobacteria while high CO2 (12%) delayed, but did not prevent the proliferation. In addition, a phylogenetically diverse array of heterotrophic α-, β- and γ-proteobacteria, Bacteriodetes along with a selection of eukaryotic microorganisms inhabited the biofilms. Principal coordinate analyses reveal unique clustering patterns indicating that the composition of the initial and the final microbial communities were distinctly different from one another. Alpha diversity measures indicated that the 16S (prokaryotic) community peaked around day 10 / 11 at both 0.04% and 12% CO2. However, unlike the 18S (eukaryotic) community where diversity was at a maximum at the end of the 26-day time-course, prokaryotic diversity achieved minimum values, particularly for biofilms grown at 0.04% CO2, where the cyanobacteria proliferated. In spite of the planned experimental design bias toward S. obliquus biofilm growth, the collective data suggest that selection against undesirable microorganism also needs to be incorporated as an essential feature of biofilm photobioreactor design and operation.
       
  • Nutrient removal from swine wastewater with growing microalgae at various
           zinc concentrations
    • Abstract: Publication date: March 2020Source: Algal Research, Volume 46Author(s): Xiang Li, Chunping Yang, Guangming Zeng, Shaohua Wu, Yan Lin, Qi Zhou, Wei Lou, Cheng Du, Lijun Nie, Yuanyuan ZhongAbstractCoelastrella sp. grows well in swine wastewater, and could remove nutrients from swine wastewater. Some typical pollutants such as Zn(II) in swine wastewater might affect the growth of microalgae and the nutrient removal performance. In this study, Coelastrella sp. was cultivated in swine wastewater at various Zn(II) concentrations, and the nutrient removal capacity and physiological and biochemical properties of the microalgae were examined to better apply this technology for the removal and recovery of nutrients from swine wastewater. Results revealed that excessive Zn(II) in swine wastewater inhibited microalgae growth and reduced the increase of pH value, thus decreased ammonia nitrogen volatilization and assimilation. Remarkably in swine wastewater, Zn(II) decreased the removal efficiency of phosphorus at low Zn(II) concentration, and promoted phosphorus precipitation and stimulated assimilation of phosphorus by Coelastrella sp. at high Zn(II) concentration. Hence in this study, we elucidated the mechanisms of nutrient removal from swine wastewater by the microalgae Coelastrella sp. in the stress of Zn(II). This study could be referred in future improvement and applications of microalgae culturing in swine wastewater treatment.
       
  • Selective fractionation of free glucose and starch from microalgae using
           aqueous two-phase systems
    • Abstract: Publication date: March 2020Source: Algal Research, Volume 46Author(s): Catalina A. Suarez Ruiz, Santiago Zarate Baca, Lambertus A.M. van den Broek, Corjan van den Berg, Rene H. Wijffels, Michel H.M. EppinkMicroalgae are a promising source of lipids, pigments, proteins and carbohydrates, which are valuable compounds for many industries. However, optimal fractionation and valorization of all produced compounds is necessary to improve the economic viability of microalgae production. This paper aims to understand the fractionation of microalgae carbohydrates (free glucose and starch) in aqueous two-phase systems. Three aqueous two-phase systems were investigated to efficiently and mildly separate carbohydrates from disrupted Neochloris oleoabundans. This strain contains 16 w/w% of proteins, 48 w/w% total fatty acids and 27 w/w% carbohydrates when cultivated under saline water and nitrogen depletion conditions. The protein content decreases and the amount of fatty acids and carbohydrates increases notably under stress conditions and glucose becomes the main carbohydrate in this microalgae. Glucose is present in the disrupted microalgae as part of polymeric carbohydrates (starch) or in monomeric form (free glucose). With the aqueous two-phase system Polyethylene Glycol 400 - Cholinium dihydrogen phosphate (PEG400-ChDHp) microalgal free glucose is fractionated up to a recovery of 99% to the most hydrated bottom phase in a single step. Simultaneously, a recovery of 70% is reached for microalgal starch in the interface after two additional liquid-liquid extractions with PEG400-ChDHp. The final fractions obtained were free of pigments.Graphical abstractUnlabelled Image
       
  • Development and validation of a rapid LC-MS/MS method for the
           quantification of mycosporines and mycosporine-like amino acids (MAAs)
           from cyanobacteria
    • Abstract: Publication date: March 2020Source: Algal Research, Volume 46Author(s): Vanessa Geraldes, Lívia S. de Medeiros, Fernanda R. Jacinavicius, Paul F. Long, Ernani PintoMycosporines and mycosporine-like amino acids are ultra-violet radiation absorbing compounds produced by lichens, fungi, algae and cyanobacterial species, especially upon exposure to solar ultraviolet radiation. These compounds are photoprotective and some have additional antioxidant functions. Thus, mycosporine-like amino acids may be used as an active ingredient in cosmetic products. Analysis is generally achieved by separation using reverse-phase chromatography and, detection and quantification based upon characteristic absorption spectra and extremely high molar extinction coefficients. Herein, a validated liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) quantification method for mycosporine-like amino acids is presented. Additionally, an easy-to-handle and rapid extraction procedure was developed, which uses only water and volatile additives as the extractor solvents. The LC-MS/MS method was performed with an electrospray ionization source in positive mode using multiple reaction monitoring with a reverse-phase column. The method enabled the accurate determination and quantification of the mycosporine-like amino acids porphyra-334, shinorine and mycosporine-glycine-alanine in a 6 min running time, with detection limits of 0.002 μg mg−1, 0.001 μgmg−1 and 0.005 μg mg−1, respectively. These methods provided a simple extraction and rapid analysis procedure that efficiently identified and quantified these three mycosporine-like amino acids produced by a collection of 29 cyanobacteria. Although more mycosporine-like amino acids have also been identified, the validated method was developed focusing on the most abundant mycosporine-like amino acids produced by the investigated cyanobacteria. Mycosporine-like amino acids could be detected at levels well above the limits of detection for the LC-MS/MS method in 12 strains, irrespective of whether the cultures had been exposed to ultra-violet radiation. High levels of constitutive expression of mycosporine-like amino acids in cyanobacteria has rarely been reported and provides an opportunity to study mechanisms that regulate ultra-violet radiation induced mycosporine-like amino acids biosynthesis in the future.Graphical abstractUnlabelled Image
       
  • C-phycocyanin extraction from two freshwater cyanobacteria by freeze thaw
           and pulsed electric field techniques to improve extraction efficiency and
           purity
    • Abstract: Publication date: March 2020Source: Algal Research, Volume 46Author(s): Supenya Chittapun, Veasarach Jonjaroen, Katsaya Khumrangsee, Theppanya CharoenratAbstractC-phycocyanin was extracted from Nostoc commune TUBT05 and Oscillatoria okeni TISTR8549 using freezing and thawing and pulsed electric field treatments. The results confirmed that freezing and thawing can be used to extract c-phycocyanin from both cyanobacterial strains, whereas pulsed electric field treatment can be used only with N. commune, whose cell structure allows extraction by this technology. The number of freeze/thaw cycles, the extraction solution used and the number of electric pulses had statistically significant influences on c-phycocyanin concentration, purity, yield and the total protein content in the crude extracts (p ≤ 0.005). Exposure of N. commune to three cycles of freeze/thaw in sodium-phosphate buffer yielded the highest c-phycocyanin content, purity, and yield. The results suggest that careful selection of both the number of freeze/thaw cycles and the extraction solution is required to ensure high productivity. Transmission electron microscopy micrographs confirmed that the cell wall structure and organization of the thylakoid were different in the two species, requiring a significantly different number of freeze/thaw cycles and pulse applications for optimal c-phycocyanin extraction. Both cyanobacterial strains were shown to be potential alternative strains for c-phycocyanin production. However, further work is needed to improve c-phycocyanin concentration and purity. We suggest that this will require refinement of the cultivation conditions and improved purification processes.
       
  • Effects of Vibrio cholerae on fatty acid profiles in
           Isochrysis galbana
    • Abstract: Publication date: March 2020Source: Algal Research, Volume 46Author(s): Ceres A. Molina-Cárdenas, Alexei Fedorovish Licea-Navarro, M. del Pilar Sánchez-SaavedraAbstractWe determined the effects on metabolism and fatty acid profiles in Isochrysis galbana when co-cultured with Vibrio cholerae. Monospecific cultures of I. galbana did not experience any changes in cell density, growth rate, organic dry weight, heterotrophic bacteria, chlorophyll a content, maximun electron transport rate (ETRm) or maximum photochemical quantum yield of photosystem II (Fv/Fm) values when co-cultured with V. cholerae. The growth of pathogenic V. cholerae was inhibited in co-cultures and the lipid content was higher compared to the monospecific cultures of I. galbana. The I. galbana-V. cholerae co-cultures had similar total saturated fatty acids (SFAs) content (53.2%) versus I. galbana cultures (55.6%). Total monounsaturated fatty acids (MUFAs) content was higher in monospecific I. galbana cultures than in the co-cultures. The total polyunsaturated fatty acids (PUFAs) content was higher in co-cultures (23.2%) versus monospecific cultures (15.9%). The interaction between I. galbana and V. cholerae altered the fatty acid levels in I. galbana cells and increased the production of linoleic acid (C18:2), linolenic acid (C18:3), gamma-linolenic acid (C18:3n6), eicosatrienoic acid (C20:3n-3), and eicosatetraenoic acid (C20:4).
       
  • Overexpression of Chlamydomonas reinhardtii LCIA (CrLCIA) gene increases
           growth of Nannochloropsis salina CCMP1776
    • Abstract: Publication date: March 2020Source: Algal Research, Volume 46Author(s): Jayaraman Vikramathithan, Kwon Hwangbo, Jong-Min Lim, Ka-Min Lim, Da Yeon Kang, Youn-Il Park, Won-Joong JeongAbstractMost aquatic photosynthetic organisms have developed inorganic carbon-concentrating mechanisms (CCMs) to compensate for the kinetic constraints of CO2 concentration in the vicinity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), which functions in the first steps of carbon fixation. CCMs, which are widespread in various types of algae, evolved independently among algal lineages and accordingly play a fundamental role in algal photosynthesis, metabolism, growth, and biomass production. Nannochloropsis, a marine eustigmatophycean microalga, is a candidate organism for biofuel production due to its high lipid content; however, inorganic carbon (Ci) availability in Nannochloropsis cells is not sufficient for complete carbon fixation due to inherently weak CCM machinery, including a CO2-leaking HCO3− pump. CrLCIA, a member of the formate-nitrite transporter family, functions as a HCO3− transporter in Chlamydomonas reinhardti. Thus, in this study, we overexpressed the CrLCIA gene heterologously in N. salina CCMP1776 in an attempt to reinforce its bicarbonate transport activity. CrLCIA expression in N. salina increased intracellular Ci and carbonic anhydrase (CA) activity, resulting in increased growth (30%) and biomass (2-fold). These results indicate that constitutively expressed CrLCIA leads to increased Ci uptake and CA activity, contributing to high availability of CO2 for photosynthesis under low CO2 conditions. The total fatty acid (FA) per cell mass in the transgenic lines was similar to that of wild-type Nannochloropsis cells, indicating that total FA productivity in the transgenic lines is increased approximately 2-fold. These findings will be useful to improve the CCM function for high biomass and lipid production using genetic modification tools in Nannochloropsis species, contributing to improved biodiesel production.
       
  • Amelioration of tomato plants cultivated in organic-matter impoverished
           soil by supplementation with Undaria pinnatifida
    • Abstract: Publication date: March 2020Source: Algal Research, Volume 46Author(s): María Florencia Salcedo, Silvana Lorena Colman, Andrea Yamila Mansilla, María Alejandra Martínez, Diego Fernando Fiol, Vera Alejandra Alvarez, Claudia Anahí CasalonguéAbstractRising demands of food together with modern practices in agriculture require the inclusion of areas with sub-optimal soil qualities for cultivation and the replacement of contaminant chemical fertilizers. In this work, we evaluated the use of the seaweed Undaria as a soil amendment of organic-matter impoverished soil. We demonstrated that Undaria supplementation to a substrate containing vermiculite:organic soil mix (95:5) promotes the growth of tomato plants evidenced in increases in aerial and root biomass and the restoration of redox status. By means of chemical and functional analysis we identified in Undaria extract the presence of plant nutrients, minerals, vitamins, antioxidant capacity and phytohormone-like activities. All together these compounds would be able to promote growth and contribute to redox homeostasis in early plant developmental stages which are critical for tomato production yield. We propose Undaria supplementation as an efficient way to provide nutritional and growth promoter compounds to tomato crops growing on impoverished soils.
       
  • Melatonin facilitates the coordination of cell growth and lipid
           accumulation in nitrogen-stressed Chlamydomonas reinhardtii for biodiesel
           production
    • Abstract: Publication date: March 2020Source: Algal Research, Volume 46Author(s): Yingying Meng, Hui-yan Chen, Jiao Liu, Chun-Yang ZhangAbstractIn microalgae, the lipid accumulation under nitrogen stress is always accompanied by low photosynthetic activity and low growth rate, which adversely affects the total biomass and the lipid productivity. It is highly desirable to develop a practicable strategy for promoting lipid accumulation meanwhile minimizing the adverse effects under nitrogen stress. In this research, we investigate whether melatonin (MT, an antioxidant that protects against abiotic stress in plant cells) can mitigate the oxidative stress and enhance the lipid production in Chlamydomonas reinhardtii starchless mutants under nitrogen stress. The results of physiological and biochemical analysis indicate that exogenous MT weakens the nitrogen stress-induced oxidative damage by delaying the chlorophyll loss, activating antioxidases, reducing the lipid peroxidation. In addition, MT stimulates the biosynthesis of functional membrane lipids (monogalactosyldiacylglycerol, digalactosyldiacylglycerol and diacylglyceryl-trimethylhomoserine) and polyunsaturated fatty acids, increasing the cell response to nitrogen stress and enhancing the whole lipid biosynthesis. The 5 μM MT induces the increase of the total fatty acid methyl ester-lipid content by 35.4% (from 49.2% to 66.7% of dry weight), the biomass by 7.4% (to 0.92 g L−1), and the lipid productivity by 42.7% compared with the control groups without MT treatment. Moreover, we investigated the biodiesel properties of the lipids derived from MT-treated nitrogen-stressed cells, and the results suggest that the variation in fatty acid proportion induced by MT has little impact on the lipid's biodiesel properties. Thus, exogenous MT can facilitate the accumulation of lipids by enhancing the cellular antioxidant capability and mitigating the adverse effects of nitrogen stress.
       
  • Algal density mediates the photosynthetic responses of a marine macroalga
           Ulva conglobata (Chlorophyta) to temperature and pH changes
    • Abstract: Publication date: March 2020Source: Algal Research, Volume 46Author(s): Gang Li, Zhen Qin, Jiejun Zhang, Qiang Lin, Guangyan Ni, Yehui Tan, Dinghui ZouAbstractGrowing of macroalgae increases their biomass densities in natural habitats. To explore how the altered algal density impacts their photosynthetic responses to changes of environmental factors, we compared the photosynthesis versus irradiance characteristics of a marine green macroalga Ulva conglobata under low [2.0 g fresh weight (FW) L−1], medium (6.0 g FW L−1) and high biomass densities (12.0 g FW L−1), and under a matrix of temperatures (20, 25, 30 and 35 °C) and pH levels (7.8, 8.2 and 8.6). Increased algal densities decreased the photosynthetic O2 evolution rate among all combined temperature and pH treatments, in parallel with the decrease of light-utilizing efficiency (α, the initial slope) and maximum photosynthetic rate (Pmax) and the increase of light saturation point (EK). Rising temperature interacted with lowered pH to increase the α under low but not under high algal densities. Rising temperature increased the Pmax and decreased the EK under low algal density, but not under high density. Lowered pH promoted the Pmax and EK under all three algal densities. The increased temperature enhanced the dark respiration (Rd) and light compensation point (EC), while the altered pH showed a limited effect. Moreover, the increased algal density reduced the Rd, and had a limited effect on the EC. In addition, our results indicate that changing algal densities caused the complex photophysiological changes in responses to the temperature and pH changes, and these complex responses resolved into a close relation between Rd and Pmax across the matrix of temperatures and pH levels.
       
  • The potential productivity of the microalga, Nannochloropsis oceanica
           SCS-1981, in a solar powered outdoor open pond as an aquaculture feed
    • Abstract: Publication date: March 2020Source: Algal Research, Volume 46Author(s): Tao Li, Zishuo Chen, Jiayi Wu, Hualian Wu, Bingjie Yang, Lumei Dai, Houbo Wu, Wenzhou XiangAbstractThe microalga, Nannochloropsis, is receiving increased attention for their potential application as a biodiesel feedstock and an aquaculture feed. Nannochloropsis cultured in different environments has been shown to possess different growth characteristics and the biochemical composition. The biochemical composition are critical as they dictate applicability and profitably of the species. In the present study, the outdoor productivity of Nannochloropsis oceanica SCS-1981 was investigated in a novel open pond that was completely powered by solar-electricity. Using this technique, the maximum cell density in the solar-powered open pond was 1.1 × 108 cell mL−1, with proteins the dominant biochemical component (53.1% of dry weight). Additionally, the microalga accumulated a high content of eicosapntemacnioc acid (EPA) comprising nearly 3% of the dry weight. Probiotics, such as Phaeodactylibacter, were present in the culture pond, which was a gram-negative bacteria that has been reported to have a positive effect on the absorption and immune system of cultured animal. The results of the study indicated that N. oceanica was suitable for aquiculture feeds. The productivity of biomass was 5.8 g m−2 d−1, which was similar to traditional raceway ponds. Considering that the solar-powered open pond requires no additional energy input, the costs of culturing can be significantly reduced. This culturing method is easy to work with and would be an easy technique to be used in the culturing of Nannochloropsis as living aquaculture feeds. The study will greatly promote the low-cost cultivation of microalgae for aquaculture feed purposes.
       
  • Photoprotection mechanisms of Nannochloropsis oceanica in
           response to light stress
    • Abstract: Publication date: March 2020Source: Algal Research, Volume 46Author(s): Baobei Wang, Jing JiaAbstractLight is a pivotal environmental factor that affects the growth and productivity of photosynthetic organisms. Microalgae have evolved complex photoprotective mechanisms to circumvent damage from high light. Nannochloropsis produce approximately 4–5% eicosapentaenoic acid (EPA) of dry cell weight (dwt) under favorable growth conditions, and accumulate triacylglycerol (TAG) at up to 60% of dwt under nutrient-depletion and high light intensities. Nannochloropsis is becoming a strong research model for oleaginous microalgae and an excellent candidate for biofuel production. To study the photoprotective mechanisms of Nannochloropsis, proteomic and physiological dynamics were tested under different light intensities. When exposed to high light stress N. oceanica IMET1 cells showed a 45% and 38% decrease in total protein and sugar content, respectively, and a 44% increase in total lipid content; the growth of cells was not affected. Cell pigment content varied substantially: chlorophyll a and violaxanthin concentrations decreased by>50%, while β-carotene, zeaxanthin, astaxanthin, and canthaxanthin increased transiently by>2-fold. Isobaric tags for relative and absolute quantification (iTRAQ) was used to label samples, and 452 proteins were identified from tandem mass spectrometry data. In response to high light stress, 150 of these proteins were significantly up-regulated and 58 were significantly down-regulated. The proteins were involved in pathways that include photosynthesis, pyruvate metabolism, and fatty acid biosynthesis. Results also indicate that photochemical adjustments in carbon metabolism, in particular, glycolysis, the Calvin cycle, and the citric acid (TCA) cycle, were activated to divert more acetyl-CoA towards carotenoid biosynthesis. This could be to scavenge reactive oxygen species to alleviate photodamage. A regulatory photoprotective model for N. oceanica IMET1 was proposed, which includes strategies of down-regulating light-harvesting antenna proteins, up-regulating oxidases, enhancing de-epoxidation within the xanthophyll cycle, accumulation of antioxidants, modulation of photosynthetic apparatus, and repartitioning of photosynthetic carbon into storage carbon.
       
  • Microalgae: A potential sustainable commercial source of sterols
    • Abstract: Publication date: March 2020Source: Algal Research, Volume 46Author(s): Ankitha Randhir, Damian W Laird, Garth Maker, Robert Trengove, Navid Reza MoheimaniAbstractMicroalgae are important natural sources of interesting high value compounds that could be used in pharmaceutical and nutraceutical applications. Of particular interest is the production and exploitation of microalgal phytosterols; compounds with known biological benefits such as cholesterol reduction, anti-inflammatory activity and even anti-cancer properties. The global market for phytosterols is expected to reach $USD 935 million by 2022. Phytosterols of commercial importance are β-sitosterol, campesterol, brassicasterol, stigmasterol and ergosterol. The current sources of phytosterols are the vegetable and tall oils harvested from land plants. However, it is anticipated that the terrestrial sources will not be able to meet increased demand through 2030 and beyond. Calculations of estimated lipid and phytosterol productivity suggest that microalgae could yield 678–6035 kg. ha−1. y−1 of phytosterol which is more than the current productivity of phytosterols from rapeseed plants, highlighting the economic potential for sourcing phytosterols from environmentally sustainable saline microalgae production. However, there are many challenges that need to be met. The sterol content of microalgae varies according to species and, at present, there is little information on how to manipulate culturing conditions to enhance sterol production in microalgae. Approaches could include nutrient limitation, and/or changing salinity, light and temperature. Molecular approaches such as genetic modification, knocking down or over expression of specific genes and blocking competitive biosynthetic pathways would be desirable. However, an improved understanding of the pathway of sterol biosynthesis in microalgae is necessary for effective use of these molecular approaches. This paper discusses the potential for sterol production from microalgae as an adjunct to current plant-based sources and highlights those areas where we need more information to produce these high value products in an environmentally and economically sustainable fashion.
       
  • Investigating the impact of inoculum source on anaerobic digestion of
           various species of marine macroalgae
    • Abstract: Publication date: March 2020Source: Algal Research, Volume 46Author(s): Oluwatosin Obata, Arlene Ditchfield, Angela Hatton, Joseph AkunnaAbstractThis study investigated the intrinsic biodegradation potential of marine organic sediment for effective biogas production from various species of marine macroalgae and non-marine biomass. Biogas production potential tests were carried out on three species of seaweed harvested from the west coasts of Scotland, Laminaria digitata, Fucus serratus, and Saccharina latissima, and on a non-marine cellulose biomass seeded with uncultivated and unadapted anoxic marine sediments. As a comparison, the same experiments were repeated using the same substrates but seeded with active mesophilic anaerobically digested sewage sludge. For the cultures seeded with anoxic marine sediments, the highest methane yield was observed in both L. digitata and S. latissima cultures while F. serratus and cellulose, cultures performed relatively poorly. For those seeded with digested sludge, all cultures performed relatively well, except F. serratus. These results show that marine sediments can be effective inoculum for seaweeds digestion. Phylogenetic analyses of the methanogenic community in both sources of inoculum showed that the methanogen community within the sediment and sludge seeded cultures were different. Each culture was dominated by methanogenic populations suitable for the utilisation of the specific biomass derivatives and environmental conditions. For instance, members of the genus Methanosaeta which, dominated sludge seeded cultures were not detected in the sediment seeded cultures. A similar occurrence was observed for the genus Methanofollis which was only detected in the sediment seeded cultures. Hence, in areas where seaweed forms part of a co-digestion with non-marine biomass, start-up using a mixture of anoxic marine sediments and digested wastewater sludge has the potential to provide greater process stability and robustness than using either as sole inoculum.
       
  • Arginine-fed cultures generates triacylglycerol by triggering nitrogen
           starvation responses during robust growth in Chlamydomonas
    • Abstract: Publication date: March 2020Source: Algal Research, Volume 46Author(s): Jacob Munz, Yuan Xiong, Jaoon Young Hwan Kim, Young Joon Sung, Seungbeom Seo, Ran Ha Hong, Thamali Kariyawasam, Nolan Shelley, Jenny Lee, Sang Jun Sim, EonSeon Jin, Jae-Hyeok LeeAbstractUnder nitrogen (N) starvation, certain microalgae increase carbon storage in the form of lipid droplets while also downregulating photosynthesis and eventually terminating growth. To improve lipid yield, we asked whether lipid droplets and N starvation responses can be induced without limiting growth or photosynthesis. In the chlorophyte Chlamydomonas reinhardtii, N starvation induces gametogenesis alongside lipid droplet accumulation, and gametogenesis has been observed in arginine-fed cultures wherein the arginine was provided as the sole N source. We therefore assessed whether arginine-fed cultures displayed N starvation responses other than gametogenesis in mixo- and phototrophic conditions, representing two primary modes of nutrition that may affect N starvation responses. We showed that arginine-fed cultures using two lab strains of C. reinhardtii supported normal mixotrophic growth, constitutively turned on N starvation-induced genes at the equivalent level to N-starved cells, and increased the triacylglycerol content of total fatty acids by 125–400% relative to ammonium-fed cultures. The lipid profile of triacylglycerol in these arginine-fed mixotrophic cultures exhibited 3 to 5.5-fold enrichment of saturated and monounsaturated fatty acids, a preferred characteristic of biodiesel precursors. Arginine-fed phototrophic cultures likewise turned on N starvation-induced genes, accumulated lipid droplets, and led to a 50% reduced growth rate per day while reaching a 3 to 6.5-fold more cell density at the stationary phase relative to ammonium-fed cultures. To test the applicability of our result to algae outside the green lineage, we conducted similar experiments with the diatom Phaeodactylum tricornutum, which also accumulated 2 to 7-fold more neutral lipids in arginine-fed phototrophic cultures without growth impairment relative to nitrate-fed cultures. We document a system wherein N starvation responses are induced without compromising photosynthesis or growth, thereby suited to the production of valuable chemicals and biofuel precursors without requiring stressors in microalgae.
       
  • Nuclear proteome analysis of Chlamydomonas with response to CO2
           limitation
    • Abstract: Publication date: March 2020Source: Algal Research, Volume 46Author(s): Carolina Arias, Ogonna Obudulu, Xiaoling Zhao, Preeti Ansolia, Xueyang Zhang, Suman Paul, Joakim Bygdell, Mohammad Pirmoradian, Roman A. Zubarev, Göran Samuelsson, Gunnar Wingsle, Amit K. BajhaiyaAbstractChlamydomonas reinhardtii is a unicellular green alga that can survive at a wide range of inorganic carbon (Ci) concentrations by regulating the activity of a CO2-concentrating mechanism (CCM) as well as other cellular functions. Under CO2 limited conditions, C. reinhardtii cells display a wide range of adaptive responses including changes in photosynthetic electron transport, mitochondria localization in the cells, the structure of the pyrenoid starch sheath, and primary metabolism. In addition to these functional and structural changes, gene and protein expression are also affected. Several physiological aspects of the CO2 response mechanism have been studied in detail. However, the regulatory components (transcription factors and transcriptional regulators) involved in this process are not fully characterized. Here we report a comprehensive analysis of the C. reinhardtii nuclear proteome using liquid chromatography electrospray ionization spectrometry (LC-ESI-MS). The study aims to identify the proteins that govern adaptation to varying CO2 concentrations in Chlamydomonas. The nuclear proteome of C. reinhardtii cells grown in the air at high (5%) and low (0.04%) CO2 concentrations were analyzed. Using this approach, we identified 1378 proteins in total, including 90 putative transcription factors and 27 transcriptional regulators. Characterization of these new regulatory components could shed light on the molecular mechanisms underlying acclimation to CO2 stress.
       
  • Impact of ocean acidification on the metabolome of the brown macroalgae
           Lobophora rosacea from New Caledonia
    • Abstract: Publication date: March 2020Source: Algal Research, Volume 46Author(s): Julie Gaubert, Riccardo Rodolfo-Metalpa, Stéphane Greff, Olivier P. Thomas, Claude E. PayriMacroalgae are critical components of coral reef ecosystems. Yet, they compete for space with corals, and in case of environmental disturbances, they are increasingly involved in phase-shifts from coral-dominated to macroalgae-dominated reefs. As regard to climate change, ocean acidification (OA) has been shown to be detrimental to corals and could favor macroalgal proliferations. However, little is known about the effects of OA on macroalgal phenotypes. Comparative metabolomic studies are particularly relevant to assess phenotypic responses of macroalgae to stress as some seaweed are known to produce a large diversity of specialized metabolites involved in various ecological functions. The main aim of our study was to explore the impact of OA on the metabolome of brown macroalgae using Lobophora rosacea as a model species. This species is widespread in New Caledonian lagoons where it is a key component of coral-algal interactions. Metabolomic changes were analyzed using Liquid Chromatography-Mass Spectrometry (UPLC-HRMS) applied to three different OA scenarii: low and variable pH over a long-term timescale (in situ at Bouraké), low and constant pH over a short-term timescale (ex situ experiment), and current pH (control). Different metabotypes were defined in diverse pH conditions, and a significant decrease in some specialized metabolites concentrations was noticed at low pH including lobophorenols B and C as well as other oxylipin derivatives. We suggest a down-regulation of metabolic pathways involving lobophorenols, in low pH conditions, or their transformation, which is in accordance with the optimal defense theory. In addition, we used Microtox® bioassays as a proxy for macroalgal toxicity and found no significant differences between low pH and control samples. This study details the first metabolomic-based study on a fleshy macroalgae in response to OA and provides new insights for this important functional group producing a large number of metabolites in response to their close environment.Graphical abstractUnlabelled Image
       
  • CSO – A sequence optimization software for engineering chloroplast
           expression in Chlamydomonas reinhardtii
    • Abstract: Publication date: March 2020Source: Algal Research, Volume 46Author(s): Iddo Weiner, Yael Feldman, Noam Shahar, Iftach Yacoby, Tamir TullerAbstractAlgal chloroplasts are promising hosts for expression of heterologous proteins. In contrast to the nuclear genome, these organelles lack transgene silencing mechanisms, making them more susceptible to genetic manipulation. While it is well established that codon selection greatly affects heterologous expression, a chloroplast-specific software for application of different sequence optimization algorithms is still missing. In this work we built CSO - a graphical user interface allowing users to engineer their genes for chloroplast expression in the model microalga Chlamydomonas reinhardtii. Within the software, users can choose between three different powerful codon selection algorithms which were built specifically for chloroplast expression: Optimal codons and folding, ChimeraMap, and Mimic original host. To provide users with general intuition regarding the performance of these algorithms, we designed different mCherry reporter genes, using each of the software algorithms. We transformed and expressed each of them in the chloroplast of C. reinhardtii, and quantified protein and mRNA abundance, alongside overall growth rates. For the reporter tested here, Mimic original host yielded the best results, though it had a lower Codon Adaptation Index score; while the algorithm supporting the highest expression could change depending on the target gene, our observations show that matching the chloroplast codon usage bias alone does not necessarily maximize expression, and that optimizing more complex sequence features could prove beneficial. CSO is freely available online; a link to its installation and download page is given in Section 3.1.
       
  • Nutrient recycle from algae hydrothermal liquefaction aqueous phase
           through a novel selective remediation approach
    • Abstract: Publication date: March 2020Source: Algal Research, Volume 46Author(s): Peter H. Chen, Juan L. Venegas Jimenez, Steven M. Rowland, Jason C. Quinn, Lieve M.L. LaurensAlgae have received increasing interest in the past several decades as a biofuel feedstock source. However, sustainable nutrient supply has presented algal biofuels with a major obstacle in the value chain. At a scale where algal biofuels would meet a significant portion of transportation fuel needs, the demand for nutrients, specifically nitrogen and phosphorus, would exceed current global agricultural production. One downstream conversion pathway, hydrothermal liquefaction (HTL), produces bio-crude oils from wet algal biomass with a waste aqueous phase (HTL-AP), containing a significant amount of carbon and nitrogen. While this stream is rich in organic content and nutrients, it also contains toxic components, which include heterocyclic nitrogen compounds and phenolic compounds. Thus, the recyclability and potential toxicity of HTL-AP need to be studied in detail. The feasibility of utilizing nutrients available in HTL-AP was experimentally determined for Chlorella vulgaris and Desmodesmus armatus monocultures. Our work focused on determining the tolerance of these algae species toward HTL-AP toxicity through varying dilutions. Nitrogen replacement in the growth media was varied from a low of 18% to a high of 141% across both species. The most notable of these results show that addition of a 100× dilution (35% nitrogen replacement) of untreated HTL-AP decreased growth in C. vulgaris by 47 ± 7% with respect to a control medium. Adsorption treatments, including activated carbon and various resins, were introduced to remediate the HTL-AP toxic effects. Treatment of the HTL-AP portion with an ion-exchange resin, Dowex 50WX8, supported C. vulgaris growth at a 100× dilution (35% nitrogen replacement) with no statistical change compared to the control. An in-depth molecular profiling demonstrated for the first time the selective removal of high‑nitrogen containing components by resin treatment. This work provides a foundation for studying the toxic components of HTL-AP and possible mechanisms by which treatments can remove these components.Graphical abstractUnlabelled Image
       
  • Antioxidant assessment of wastewater-cultivated Chlorella sorokiniana in
           Drosophila melanogaster
    • Abstract: Publication date: March 2020Source: Algal Research, Volume 46Author(s): Shuang Qiu, Yeting Shen, Liang Zhang, Bin Ma, Ayesha A. Amadu, Shijian GeAbstractMicroalgae play a critical role as a sustainable and abundant source of natural antioxidant compounds, leading to a potential market for microalgae-based food or feed supplements. Currently, this market development is limited by high cost of biomass production due to the large quantities of water and nutrients required for microalgae cultivation. It has been demonstrated that this barrier could be overcome by microalgae cultivated in wastewater containing nutrients. However, there is a pressing need to investigate how the wastewater medium influences antioxidant characteristics of microalgae. This study examined the antioxidant effects of wastewater-cultivated microalgae Chlorella sorokiniana (C. sorokiniana) using Drosophila melanogaster (fruit fly) as the animal model. Characteristics representing antioxidant properties such as fly lifespan, behavioral activities and stress resistance capacities, together with the potential underlying antioxidant mechanism were assessed. Results showed that flies fed on 4 mg/mL wastewater-cultivated C. sorokiniana had significantly extended median lifespan (55 days vs 49 days for control), and improved locomotor activity with increased step size and longer travel distance, although no significant differences in struggling activity was observed. Moreover, C. sorokiniana diet provided flies with protective responses to both H2O2-induced oxidative stress and anoxia-induced disturbance on brain ion homeostasis. These aforementioned effects were associated with the mRNA up-regulation of endogenous stress-defense genes such as Cu/Zn-superoxide dismutase (SOD1) and catalase (CAT) as well as the down-regulation of Methuselah (MTH) gene. Finally, flies fed on C. sorokiniana demonstrated similar feeding behavior and boundary preference, suggesting that C. sorokiniana supplementation did not cause starvation. This study demonstrated that C. sorokiniana grown on wastewater still maintained antioxidant properties in fruit fly, further providing new insights into the feasibility of wastewater-grown microalgae as a natural antioxidant alternative.
       
  • Parallelisable non-invasive biomass, fitness and growth measurement of
           macroalgae and other protists with nephelometry
    • Abstract: Publication date: March 2020Source: Algal Research, Volume 46Author(s): Benoît Calmes, Martina Strittmatter, Bertrand Jacquemin, Marie-Mathilde Perrineau, Céline Rousseau, Yacine Badis, J. Mark Cock, Christophe Destombe, Myriam Valero, Claire M.M. GachonAbstractWith the exponential development of algal aquaculture and blue biotechnology, there is a strong demand for simple, inexpensive, high-throughput, quantitative phenotyping assays to measure the biomass, growth and fertility of algae and other marine protists. Here, we validate nephelometry, a method that relies on measuring the scattering of light by particles in suspension, as a non-invasive tool to measure in real-time the biomass of aquatic micro-organisms, such as microalgae, filamentous algae, as well as non-photosynthetic protists. Nephelometry is equally applicable to optic density and chlorophyll fluorescence measurements for the quantification of some microalgae, but outperforms other spectroscopy methods to quantify the biomass of biofilm-forming and filamentous algae, highly pigmented species and non-photosynthetic eukaryotes. Thanks to its insensitivity to the sample's pigmentation, nephelometry is also the method of choice when chlorophyll content varies between samples or time points, for example due to abiotic stress or pathogen infection. As examples, we illustrate how nephelometry can be combined with fluorometry or image analysis to monitor the quantity and time-course of spore release in fertile kelps or the progression of symptoms in diseased algal cultures.
       
  • Algal cell lysis by bacteria: A review and comparison to conventional
           methods
    • Abstract: Publication date: March 2020Source: Algal Research, Volume 46Author(s): Meng Wang, Shibao Chen, Wenguang Zhou, Wenqiao Yuan, Duo WangAbstractThe lysis or disruption of eukaryotic, unicellular algae by bacteria and other conventional methods is important for both algal bloom control and biofuel production. This study was aimed to synthesize and analyze the current knowledge and research about algal cell lysis, with a special emphasis on bacteria-algae interactions. A brief review of algal lysis by conventional methods including mechanical and non-mechanical methods was first introduced, then the current knowledge about the isolation and classification of algicidal bacteria, the possible algicidal mechanisms, prey preferences, and potential applications were summarized. Approximately 70% of the algicidal bacteria lyse algae by indirect attack, with the rest requiring direct contact with the target prey, and algae species specificity is not evident among various algicidal bacteria. Mechanistic knowledge about the lysis effects of algicidal bacteria on their prey is still deficient, owing to the limitations of current techniques for identifying the interactions of algae and algicidal bacteria at various levels, from molecular to cellular and population scales. The advantages and disadvantages of algicidal bacterial cell lysis versus conventional non-biological methods were discussed. Potential ways to address the drawbacks of bacteria-based algal cell lysis for biofuel production were proposed.
       
  • Axenic cyanobacterial (Nostoc muscorum) biofilm as a platform for Cd(II)
           sequestration from aqueous solutions
    • Abstract: Publication date: March 2020Source: Algal Research, Volume 46Author(s): Prashanth S. Raghavan, Akhilesh A. Potnis, Kaustava Bhattacharyya, Darshana A. Salaskar, Hema RajaramAbstractAn environment friendly approach towards heavy metal remediation from water is the need of the hour. A novel approach to heavy metal bioremediation from water was attempted using axenic cultures of the photoautotrophic cyanobacterium, Nostoc muscorum immobilised on to glass surface through the formation of biofilms. Being a biofilm, it exhibited much higher cellular integrity than cell suspension cultures when exposed to high concentrations of cadmium, and could also withstand the harsh conditions prevalent in industrial effluents. Being a photosynthetic organism, culturing of N. muscorum as a biofilm was achieved with minimal requirements, such as water with minerals, light and stationary conditions, which also enabled ease of scalability. The strong adherence of the N. muscorum biofilm to the glass surface was beneficial as (i) no diffusion of cell mass on to the media was observed even with the use of top-end stirrer, (ii) no expensive separation techniques were required for separation of biomass from the treated solution, and (iii) direct contact of the solution containing metals to the active components on biofilm surface allowed better interaction. The N. muscorum biofilm exhibited the capability to sequester Cd(II) in the pH range 5–9, concentration range C=O and>C=N functional groups, and followed the Langmuir's adsorption isotherm. It is proposed to use the N. muscorum biofilm as a potential green technology for waste water treatment in future.
       
  • Bioplastic feedstock production from microalgae with fuel co-products: A
           techno-economic and life cycle impact assessment
    • Abstract: Publication date: March 2020Source: Algal Research, Volume 46Author(s): Braden D. Beckstrom, Michael H. Wilson, Mark Crocker, Jason C. QuinnThe current and future consumption of petroleum-based plastics, which will be 20% of global annual oil comsumption by 2050, is leading to the investigation and development of feedstock alternatives. Algae-based plastics offer a promising substitute that would decrease oil consumption, improve environmental impact, and in some cases even improve plastic performance. This study investigates the economic viability and environmental impact of an algae biorefinery that integrates the complementary functions of bioplastic feedstock (BPFS) and fuel production. The BPFS and biofuel biorefinery modeled herein includes nine different production scenarios. Performance of the facility was validated based on experimental systems with modeling work focusing on mass and energy balances of all required sub-processes in the production pathway. Results show that the minimum selling price of the BPFS is within the realm of economic competition with prices as low as $970 USD tonne−1. Additionally, life cycle impact assessment results indicate drastic improvements in performance of the produced BPFS, with reductions in greenhouse gas emissions ranging between 67 and 116% compared to a petroleum-based plastic feedstock. These results indicate that an algae biorefinery focused on BPFS production and fuels has the potential to operate both economically and sustainably. Sensitivity analysis results, alternative co-products (given that fuels represent minimal value) and product market potential are also discussed.Graphical abstractUnlabelled Image
       
  • The intracellular water volume modulates the accumulation of cadmium in
           Euglena gracilis
    • Abstract: Publication date: March 2020Source: Algal Research, Volume 46Author(s): Rosina Sánchez-Thomas, Jorge D. García-García, Álvaro Marín-Hernández, Juan P. Pardo, Sara Rodríguez-Enríquez, Rosario Vera-Estrella, Ambar López-Macay, Rafael Moreno-SánchezIn order to describe a relatively novel mechanism associated to heavy metal resistance in Euglena gracilis, the osmotic responses during cadmium accumulation were analyzed. Several physiological/biochemical parameters were assessed in E. gracilis exposed to 50 and 200 μM Cd2+, concentrations well within the range found in polluted soils and aquatic environments. The Cd2+ accumulation attained after only 24 h exposure induced marked increases in both the intracellular water volume and cellular size, which were maintained for several days; these changes correlated with (i) an increased intracellular osmolarity (i.e. osmotic pressure) driven by a generalized increase in the osmo-metabolites (trehalose, phosphate-molecules, amino acids, thiol-molecules, betaines and polyamines) content; and (ii) the triggering of antioxidant defenses (increased GSH/GSSG ratios and GPx, GR and APx activities). In contrast, no changes in intracellular volume, cellular size and antioxidant status were observed under hyperaccumulation of Zn2+. Furthermore, E. gracilis cultured in a hypoosmotic medium promoted greater Cd2+ accumulation and water volume, compared to a hyperosmotic medium. These changes were significantly decreased by the aquaporin inhibitors Hg2+ and pentamidine. The results suggested that the cell responses to Cd2+ and osmotic stress share biochemical mechanisms in this algae-like protist, in which Cd2+ accumulation closely correlates with the intracellular water volume changes in an oxidative stress-mediated process.Graphical abstractUnlabelled Image
       
  • A strategy for stimulating astaxanthin and lipid production in
           
    • Abstract: Publication date: March 2020Source: Algal Research, Volume 46Author(s): Litao Zhang, Chunhui Zhang, Jianguo Liu, Na YangIn large-scale outdoor cultivation, Haematococcus pluvialis cultures are frequently exposed to low light caused by continuous rain conditions. Low light significantly restricts biomass and astaxanthin accumulation, thereby decreasing astaxanthin productivity. In this study, the effects of exogenous glycerol on the growth, photosynthesis, and astaxanthin and lipid accumulation in H. pluvialis under low light were investigated. A strategy was developed for promoting astaxanthin and lipid production in H. pluvialis under low light by the application of exogenous glycerol. Under low light, exogenous glycerol did not change the biomass and photosynthetic capacity of H. pluvialis. The addition of 1 mL L−1 glycerol increased total lipid content by 36.8% by increasing the formation of fatty acids during an 11-day growth period. Furthermore, exogenous glycerol could directly accelerate astaxanthin production under low light by increasing the formation of substrates (e.g. pyruvate). Meanwhile, the elevated fatty acid level due to the addition of glycerol facilitated the esterification of astaxanthin, thereby accelerating the biosynthesis of astaxanthin indirectly, which is indicated by the fact that exogenous glycerol enhanced astaxanthin esters content significantly under low light. All these results suggest that H. pluvialis has the ability to utilize glycerol for astaxanthin and lipid production under low light.Graphical abstractUnlabelled Image
       
  • Primary metabolism is associated with the astaxanthin biosynthesis in the
           green algae Haematococcus pluvialis under light stress
    • Abstract: Publication date: March 2020Source: Algal Research, Volume 46Author(s): Chaoyang Hu, Dandan Cui, Xue Sun, Jianxin Shi, Nianjun XuAbstractHaematococcus pluvialis is a kind of native bioresource, which accumulate high abundance of astaxanthin, one of the most important bioactive compounds, under various biotic and abiotic stress conditions particularly under high light. However, the global metabolic responses to high light in general and the relationship between primary metabolism and astaxanthin accumulation in particular are still obscure. In this study, non-targeted metabolomics approach was first to be used to profile the dynamic metabolic changes of H. pluvialis along astaxanthin accumulation under different light intensities, in which>200 low molecular metabolites were identified. The integration of metabolomics data with previous transcriptomic data uncovered several metabolic pathways including raffinose family oligosaccharides biosynthesis pathway, GSH metabolism pathways, pyrimidine and purine metabolism pathways, TCA cycle, and phospholipids, that are important for astaxanthin biosynthesis under high light intensity, pinpointing a metabolic shift from primary metabolism to astaxanthin biosynthesis. Exogenous application of related metabolites such as nucleotides, carbohydrates and amino acids in algal medium confirmed the metabolic link between primary metabolism and astaxanthin biosynthesis. Our results provides with a solid metabolic base for the manipulation of astaxanthin production under high light stress, and reveals metabolic insights into the adaption strategy of H. pluvialis against light stress conditions.
       
  • Changes in metabolism, growth and nutrient uptake of Ulva fasciata
           (Chlorophyta) in response to nitrogen source
    • Abstract: Publication date: March 2020Source: Algal Research, Volume 46Author(s): Ben Shahar, Muki Shpigel, Roy Barkan, Matan Masasa, Amir Neori, Helena Chernov, Eitan Salomon, Moshe Kiflawi, Lior GuttmanAbstractThe form of inorganic nitrogen (N) determines the biofiltration performance of Ulva, particularly by inhibition of nitrate assimilation in the presence of ammonia. In the current study, Ulva fasciata from a biofilter of fishpond effluent was examined for its biomass production, photosynthetic activity, nutrient uptake and activity of nitrate reductase when supplied with either ammonia or nitrate as the sole nitrogen source. The effects of prior acclimation to either nitrogen source were also studied. Cultivation of Ulva with ammonia resulted in a rapid uptake of this nutrient, whereas photosynthesis, uptake of orthophosphate and C:N ratio were greater in cultures with nitrate. The transfer of Ulva from ammonia to nitrate nutrition increased carbohydrate content in the biomass. Longer culture in nitrate did not influence photosynthetic yields, growth, or N and P uptake rate by the algae, but increased both lipid and P content in biomass. Once transferred from ammonia-rich to nitrate-rich seawater, nitrate uptake by Ulva commenced immediately, although the activity of the enzyme nitrate reductase was first detected only 28 h later. Culture of Ulva in different nitrogen forms, ammonia and nitrate, may determine application of the resulting biomass in different industries, e.g., feeding, bioethanol, biofiltration, etc., considering the rapid production of protein-rich Ulva in the presence of ammonia, while yield is lower in the presence of nitrate but the biomass contains more carbohydrates and removes P from the effluent more rapidly.
       
  • Combining medium recirculation with alternating the microalga production
           strain: a laboratory and pilot scale cultivation test
    • Abstract: Publication date: March 2020Source: Algal Research, Volume 46Author(s): J. Fret, L. Roef, L. Diels, S. Tavernier, W. Vyverman, M. MichielsAbstractReuse of growth medium after biomass harvesting is a cost-saving approach to improve the economic feasibility of algae mass cultivation. Algal exudates, cell debris and varying amounts of residual nutrients, impose challenges to the recycling of spent medium. In this study, the potential of combining reused medium from different algae species for growing monocultures of other algal strains was evaluated by making use of three successive cultivation setups with increasing volume; 400 mL in turbidostat mode, 2.6 L and 220 L in semi-continuous mode. Cultivation on replenished medium derived from Nannochloropsis sp. and Tisochrysis lutea, had no adverse effect on the productivity of either of the strains, regardless of whether they were grown in their own recycled medium or that of the other alga. Microfiltration of the reused medium proved to be sufficient to avoid cross-contamination. Moreover, a substantial average reduction in water footprint (77%) and nutrient cost (68% or 9 €·kg−1 dry biomass) was achieved. Extension and validation of the medium recycling approach to other economically interesting algae species can contribute to improving the economic feasibility of large scale microalgae production systems.
       
  • The role of algae in the removal and inactivation of pathogenic indicator
           organisms in wastewater stabilization pond systems
    • Abstract: Publication date: March 2020Source: Algal Research, Volume 46Author(s): Lei Liu, Geof Hall, Pascale ChampagneAbstractWastewater stabilization ponds (WSPs) are an economical alternative to conventional wastewater treatment technologies. They are commonly favored by small and rural communities. Due to long hydraulic retention time required by the treatment in these systems, algal activity is often expected during summer season. This study investigated the effects of algal growth on the removal and inactivation of pathogenic indicator organisms in WSP systems. Two predominant algae species (Mougeotia sp. and Hydrodicty sp.) that were found in Amherstview WSP were able to increase both pH and DO. The highest inactivation rates of both E. coli and total coliforms (TC) were observed at pH 10.5 compared to other pH (4, 8, 8.5, 9.5) investigated in the bench-scale experiments. Both high (20 mg/L) and low DO (1 mg/L) levels can facilitate the removal and inactivation of both E. coli and TC. Enterococci were significantly reduced at both intermediate (8.6 mg/L) and high (20 mg/L) DO concentrations. Therefore, the presence of algae can potentially promote the removal of E. coli, TC and Enterococci. Much higher inactivation of E. coli, TC and Enterococci at a higher temperature (20 °C) than at a lower temperature (4 °C) indicates temperature is one the most important removal factor. Two potential/additional indicator organisms (Enterococci and Clostridium perfringens (C. perfringens)) exhibited different inactivation trends than the traditional indicators (E. coli and TC) under the same pH and DO conditions. C. perfringens were tolerant to all the tested pH, DO and temperature conditions. Their resistance to environmental stresses may pose potential health risk. Hence, both Enterococci and C. perfringens could be potentially used as indictor organisms to predict the overall level of pathogens in treated wastewater.
       
  • Microalgae-based nitrogen bioremediation
    • Abstract: Publication date: March 2020Source: Algal Research, Volume 46Author(s): Hui Chen, Qiang WangAbstractPollution poses an increasing threat to the environment and to human health. Nitrogen pollution is of great concern, with nitrogen oxide (NOx) in the air and ammonia nitrogen in water being two major pollutants. Culturing microalgae in NOx or wastewater with high concentrations of ammonia nitrogen would both reduce environmental pollution and provide a source of nitrogen for microalgal culture. However, for microalgae-based bioremediation to be feasible, many fundamental questions about algal biology must be addressed. This review summarizes progress in microalgal biotransformation, outlines applications of this technology, and provides an in-depth description of the current state of microalgae-based bioremediation of NOx or wastewater with high concentrations of ammonia nitrogen. Furthermore, we present possible solutions to some of the obstacles that must be overcome to realize the practical applications of microalgae-based bioremediation.
       
  • Simultaneous depolymerization and fermentation of lignin into value-added
           products by the marine protist, Thraustochytrium striatum
    • Abstract: Publication date: March 2020Source: Algal Research, Volume 46Author(s): Xiang Li, Mi Li, Yunqiao Pu, Arthur J. Ragauskas, Yi ZhengBiodegradation of lignin has been focused on bacteria and fungi, but little information is available on lignin biotransformation with marine protists. In this paper, kraft pine lignin was used as a carbon source for a newly recognized and patented lignin degrader, Thraustochytrium striatum HB. The fermentation medium was optimized in terms of nitrogen source and trace elements. The results showed NH4Cl was the best nitrogen source to enhance lignin consumption from 3 (for yeast extract or peptone) to 17%, while the utilization of yeast extract or peptone was found to inhibit lignin consumption by T. striatum HB. The presence of trace elements and vitamins improved lignin utilization from 17 to 25% by inducing the production of lignolytic enzymes. Different lignin depolymerization methods, including laccase, fungal secretome and Fenton reagent were used to enhance lignin fermentation. In the presence of laccase, both cell growth and lignin consumption were improved, and it was found that different laccases had different working mechanisms. Enzymatic depolymerization resulted in 25–30% lignin degradation, slightly higher than that (22%) from Fenton reagent. NMR analysis indicated that the fungus-derived laccase primarily worked on the breakdown of inter-unit linkages in lignin molecules, while plant-derived laccase possibly attacked the aromatic ring structures. With the function of laccase, more low-molecular-weight lignin fragments can be generated, and laccase-catalyzing reaction would direct the equilibrium toward depolymerization by preventing repolymerization of small fragments. On the contrary, lignin peroxidase-dominant fungal secretome and Fenton reagent facilitated lignin degradation but not cell growth, possibly due to the generation of inhibitory compounds from lignin depolymerization by fungal secretome and Fenton reagent. The results from this research demonstrate that marine protists, such as T. striatum HB are a class of promising platform microorganisms for lignin valorization into valuable bioproducts.Graphical abstractUnlabelled Image
       
  • The effect of functional unit and co-product handling methods on life
           cycle assessment of an algal biorefinery
    • Abstract: Publication date: March 2020Source: Algal Research, Volume 46Author(s): Deborah L. Sills, Léda Gerber Van Doren, Colin Beal, Elizabeth RaynorAbstractMicroalgae are a promising feedstock for sustainable fuel and nutritional products. To be economically viable, algal biorefineries will need to produce multiple products, such as nutraceuticals and animal feed, in addition to fuel. Life cycle assessment (LCA) has been applied widely to algal biorefineries, but results vary across studies. Here we address two methodological challenges that can lead to variability in LCAs of multi-product algal biorefineries: the choice of functional unit and the method used to handle co-products. LCA was conducted for an algal biorefinery that produces two representative products—fuel and animal feed—using three functional units: (1) 1 MJ fuel, (2) 1 kg animal feed, and (3) 1 ha of production area, coupled with the system expansion method. For the fuel-based functional unit, the system expansion method was compared to impact allocation based on mass, energy, and market value of the biorefinery products. The choice of functional unit affects the results for several environmental indicators. For ecosystem quality, the choice of functional unit can change the overall balance of environmental impacts from harmful to beneficial. The effect of functional unit on climate change depends on the boundary considered in the model—i.e., “well to gate” or “well to wheels”. When a fuel-based functional unit is used, the choice of co-product handling method (i.e., allocation versus the system expansion method) affects environmental impacts, such as ecosystem quality and climate change, differently. For LCAs that use a fuel-based functional unit to compare algal biofuel to other fuels, multiple co-product handling methods should be analyzed and presented to stakeholders. A land based functional unit coupled with the system expansion method can be used to improve LCAs that compare among multi-product algal biorefineries.
       
  • Creating a synthetic lichen: Mutualistic co-culture of fungi and
           extracellular polysaccharide-secreting cyanobacterium Nostoc PCC 7413
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Tingting Li, Liqun Jiang, Yifeng Hu, Jackson T. Paul, Cristal Zuniga, Karsten Zengler, Michael J. BetenbaughAbstractIn order to create synthetic lichens, extracellular polysaccharide (EPS)-secreting cyanobacterium Nostoc PCC 7413 was cultured together with fungal Aspergillus nidulans and Aspergillus niger species without extraneous organic carbon. Cyanobacterial supernatants and harvested EPS both supported fungal growth, while fungal supernatants slightly enhanced Nostoc growth. Furthermore, when Nostoc and A. nidulans were co-cultured together, total biomass was approximately 3-fold higher than the axenic Nostoc cultures in pH 6 buffered BG-11 media. The spectrum of fatty acids generated in co-culture differed from those of the individual cyanobacterial and fungal species. The fatty acid fractions of C18:0 and C18:1 were reduced or intermediate in co-cultures compared to mono-cultures while fractions of C16:1 and C18:3 fatty acids increased in co-culture, suggesting a shift in the fatty acid biosynthesis following co-cultivation. Our study establishes a low-cost mutualistic co-culture platform composed of cyanobacteria and filamentous fungi for producing biomass and biofuel precursors with potential commercial applications.
       
  • Perspectives and challenges of small scale plant microalgae cultivation.
           Evidences from Southern Italy
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Luigi Mennella, Domenico Tosco, Francesca Alberti, Luigi Cembalo, Maria Crescimanno, Teresa Del Giudice, Antonino Galati, Matteo Moglie, Alfonso Scardera, Giorgio Schifani, Francesco Solfanelli, Gianni CiciaAbstractIn recent years, the cultivation of algae has achieved attention of scientists and practicioniers due to the great variety of products that can be obtained, among which biofuels. The aim of this work is twofold. The first is to perform a profitability analysis of food and biofuel production from microalgae, in a small-scale setting. The second is to assess the economic impact of algae production systems on the dairy farms potentially interested in Southern Italy. The analysis was performed using financial and economic indicators and considering two system management scenarios, namely single and collective. Our results confirm that current microalgae production technology favors biofuel only as a co-product and that the production of high-value co-products improve profitability and net income in Southern Italian dairy farms, either in single or collective management. More specifically, the single management is more profitable, but the collective is more viable. The sensitivity analysis, based on the price uncertainty of algal biomass, confirms that the price of product is a critical parameter to ensure the investment feasibility in the agricultural context analyzed. Current study provides hints to entrepreneurs and managers operating in the agricultural sectors, interested in improving their firm’s performance through the adoption of a diversification strategy of business activities.
       
  • Proteomic response of Euglena gracilis to heavy metal exposure –
           Identification of key proteins involved in heavy metal tolerance and
           accumulation
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Bishal Khatiwada, Mafruha T. Hasan, Angela Sun, Karthik Shantharam Kamath, Mehdi Mirzaei, Anwar Sunna, Helena NevalainenAbstractContamination of the environment by heavy metals is an increasing problem globally. While the mechanisms bacteria and yeasts have developed to tolerate these metals are well covered in the published literature, much less is known about algae. In this study, the wild-type Euglena gracilis (Z-strain) and the sugar loving E. gracilis var. saccharophila (B-strain) were exposed to the heavy metals cadmium (Cd), lead (Pb) and mercury (Hg). Minimum inhibitory concentration (MIC) studies indicated that the heavy metal tolerance of both strains was in the order of Pb > Cd > Hg. Based on microwave plasma atomic emission spectroscopy (MP-AES), the maximum Cd accumulation by Z-strain was 8.1 mg Cd per gram of dry weight (DW), which makes it a Cd hyperaccumulator.A total of 4493 proteins were quantified by SWATH mass spectrometry to assess the effect of the heavy metals on E. gracilis at the proteome level. In response to Cd, 960 proteins in the Z-strain and 127 in the B-strain changed in relative abundance compared to the untreated control. Proteins of high abundance included the major facilitator superfamily (MFS) transporters, cadmium/zinc-transporting ATPase and heavy metal transporting P1B-ATPase. Also, there was a substantial increase in the abundance of thiol-rich proteins that are paramount in metal chelation and sequestration as well as proteins involved in cellular stress response. A potential mechanism schematic for heavy accumulation in the E. gracilis Z-strain is outlined based on the data collected. The proteomic data presented here contribute to a better understanding of the effects of the exposure of E. gracilis to heavy metals by identifying proteins and thereby genes involved in heavy metal tolerance and accumulation. The information obtained can eventually be utilized for generating highly heavy metal-tolerant Euglena strains for environmental applications.
       
  • The potential nutritive value of Sargassum fulvellum as a feed
           ingredient for ruminants
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): You Young Choi, Shin Ja Lee, Hyun Sang Kim, Jun Sik Eom, Do Hyung Kim, Sung Sill LeeAbstractThe aim of present study was to evaluate the nutritional value of Sargassum fulvellum (S. fulvellum; gulfweed, mojaban, hondawara) as a feed ingredient and investigate whether its functional metabolites could be helpful for increasing rumen fermentation characteristics. Rumen contents were collected from two rumen-cannulated Hanwoo cows (BW = 450 ± 30 kg). The in vitro trial was performed after 3, 6, 9, 12, 24, 48, and 72 h with S. fulvellum inclusion at concentrations of 1, 3, 5 and 10% of total ration. Total gas emission indicated that each S. fulvellum dose was significantly higher at 3, 6 and 9 h of incubation compared with the 0% inclusion sample but did not affect methane and carbon dioxide emission. Supplementation with 10% S. fulvellum significantly increased total volatile fatty acid (VFA) concentrations over those without supplementation. The in situ trial was performed 6, 12, 24, 48 and 72 h, with 5 g S. fulvellum, to estimate the dry matter disappearance (DMD) from the bag in the rumen. The DMD of S. fulvellum was significantly higher than that of timothy hay at 6, 12 and 24 periods. Proton nuclear magnetic resonance (1H NMR) was used to identify and quantify functional metabolites in S. fulvellum. The most abundant metabolites were guanidoacetate, ethylene glycol and alanine. Although the level of arsenic (As) in S. fulvellum was high, it was still within the acceptable limit for ruminants, and was not likely to cause any health defects, especially as S. fulvellum also contained many beneficial minerals. Overall, the inclusion of S. fulvellum as an alternative feed ingredient in ruminant diet has many potential nutritional benefits. Nevertheless, further in vitro studies using S. fulvellum and different basal diets combinations and, ultimately, in vivo studies are necessary to determine its value.
       
  • Production of extracts with anaesthetic activity from the culture of
           Heterosigma akashiwo in pilot-scale photobioreactors
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): J.J. Gallardo-Rodríguez, A. Astuya-Villalón, V. Avello, A. Llanos-Rivera, B. Krock, C. Agurto-Muñoz, A. Sánchez-Mirón, F. García-CamachoAbstractThe shear-sensitive microalga Heterosigma akashiwo is known to produce brevetoxin-like compounds that are active in voltage-dependent sodium channels. In this work, we present a study on the production of anaesthetic extracts from H. akashiwo biomass obtained in low-shear bioreactors at different growth phases. The photobioreactors (PBRs) used had specific configurations and were operated in such a way as to avoid cellular damage by hydrodynamic stress. Cultures were developed in small static-control flasks and PBRs with volumes ranging from 1.5 L to 200 L. The bioactivity of the produced extracts was assessed in vitro (Neuro-2a cell-based assay) and in vivo (Zebra fish model). Bioactivity depended slightly on the growth phase and culture system, with greater toxicity with the Neuro-2a model when stationary-phase extracts were used. Interestingly, extracts were not cytotoxic against other human cell lines. Steady production of anaesthetic bioactives was observed. In vivo anaesthetic efficacy, assessed with the Zebra fish model, was similar to that of commercial products, and without any observed mortality at 24-h post exposure.
       
  • Chlorella vulgaris in a heterotrophic bioprocess: Study of the lipid
           bioaccessibility and oxidative stability
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Greta Canelli, Lukas Neutsch, Roberta Carpine, Sabrina Tevere, Francesca Giuffrida, Zhen Rohfritsch, Fabiola Dionisi, Christoph J. Bolten, Alexander MathysMicroalgal biomass is an emerging source of several health-related compounds, including polyunsaturated fatty acids. Herein, Chlorella vulgaris was cultivated heterotrophically in a 16-L stirred tank bioreactor. The lipid oxidative stability and lipid bioaccessibility of the biomass harvested during the exponential and stationary phases were evaluated. The biomass harvested during the stationary phase showed lower lipid oxidation than that harvested during the exponential phase, likely due to the higher content of antioxidants in the former. In both biomasses, the hexanal and propanal profiles showed only moderate increase over 12 weeks of storage at 40 °C, indicating good oxidative stability. Lipid bioaccessibility measured in an infant in vitro model was 0.66% ± 0.16% and 2.41% ± 0.61% for the biomass harvested during the exponential and late stationary phases, respectively. This study indicates that C. vulgaris biomass can be considered as a stable and nutritious (optimal ω3:ω6 profile) source of essential fatty acids. Our results suggested that regarding lipid stability and bioaccessibility, harvesting during stationary phase could be preferred choice. In general, treatment of the biomass to increase lipid bioaccessibility should be investigated.Graphical abstractUnlabelled Image
       
  • Fucoidans: The importance of processing on their anti-tumoral properties
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): M.D. Torres, N. Flórez-Fernández, R. Simón-Vázquez, J.F. Giménez-Abián, J.F. Díaz, Á. González-Fernández, H. DomínguezAbstractFucoidans possess antitumoral properties, confirmed by in vitro and in vivo tests and by some clinical studies. However, the heterogeneous characteristics of these complex polysaccharides, the strong influence of collecting and processing conditions, as well as the lack of assays with standardized purified products make the comparison of available data difficult. Most in vitro tests have been performed with purified fractions, and most in vivo studies with commercial, either crude or purified, fucoidans. Molecular weight, monosaccharide composition, sulfation pattern, and the presence of other substituents are highly dependent on the extraction and purification conditions and in order to maintain active structures, the loss of sulfate and other active groups has to be avoided. This review presents information on the influence of the processing stages on the composition and antitumoral properties of fucoidans, and the relevance of other strategies, such as combination with conventional drugs or encapsulation, to enhance bioactivity.
       
  • Microalgal cell disruption: Effect on the bioactivity and rheology of
           wheat bread
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): M. Cristiana Nunes, Carla Graça, Sanja Vlaisavljević, Ana Tenreiro, Isabel Sousa, Anabela RaymundoAbstractThe aim of this study is to investigate the potential of the addition of a microalgal biomass to improve nutritional quality of bread. Microalgae contain a substantial amount of nutrients that are naturally encapsulated within cells, namely proteins, polysaccharides, polyunsaturated fatty acids and pigments (chlorophylls and carotenoids), which are capable of resisting harsh conditions during food processing. However, the cell wall integrity may significantly limit nutrient availability, and microalgal cell disruption is potentially required as a pretreatment.A suspension of a fresh Chlorella vulgaris biomass (0.88 g/L) was disrupted in a high-pressure homogenizer at 340 MPa using 1 and 4 passages. The impact of the cell disruption method was evaluated in terms of the reduction in the number of intact cells and average colony diameter of the remaining cells using flow cytometry and microscopy.Since cell disruption promotes the release of intracellular products, it can impart structural modifications to doughs and breads. Therefore, doughs and breads were prepared with the fresh C. vulgaris biomass (1.0 g of Cv/100 g of flour+Cv), the disrupted biomass, or a commercial powder. Doughs were characterized in terms of texture and oscillatory rheology. The texture and colour of breads were also evaluated. Cell wall disruption affected the colour and texture of the breads, resulting in breads with a higher firmness. Furthermore, bioactivity was evaluated, and the reducing power of the bread extracts obtained using the ferric ion reducing antioxidant power assay showed that cell disruption positively modulated the antioxidant capacity.
       
  • Effect of Arthrospira platensis (spirulina) incorporation on the
           rheological and bioactive properties of gluten-free fresh pasta
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Patrícia Fradinho, Alberto Niccolai, Rita Soares, Liliana Rodolfi, Natascia Biondi, Mario R. Tredici, Isabel Sousa, Anabela RaymundoGluten-free foods are generally nutritionally deficient and are the source of serious technological constraints. This work aimed to evaluate the technological performance of addition of two spirulina biomasses: Arthrospira platensis F&M-C256 and Ox Nature (resulting from different drying procedures) to gluten-free pastas, in terms of mechanical properties, antioxidant capacity, in vitro digestibility and sensory analysis.Texture properties of GF pasta was not significantly (p 
       
  • Hydrogen producer microalgae in interaction with hydrogen consumer
           denitrifiers as a novel strategy for nitrate removal from groundwater and
           biomass production
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Fariba Rezvani, Mohammad-Hossein Sarrafzadeh, Hee-Mock OhLow-soluble and hazardous hydrogen gas which is used in current water denitrification processes was substituted by microalgae as a novel approach for biological nitrate removal. Bioremediation of nitrate-contaminated groundwater was evaluated by three batch cultures of hydrogen consumer denitrifiers (HCD), microalgae, and HCD-microalgae consortium at a similar inoculated total biomass of about 0.025 g. Microalgae contained three species of Chlorella vulgaris, Ettlia sp., and Chlamydomonas reinhardtii with an initial cell number of 60 × 104 cell/mL and subsequently C. vulgaris as dominant strain. High nitrate concentration of about 221 mg/L was entirely removed in hydrogen-injected denitrification bioreactor containing HCD in
       
  • Sorption of paralytic shellfish toxins (PSTs) in algal polysaccharide gels
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Dave Eldon B. Olano, Lilibeth A. Salvador-Reyes, Marco Nemesio E. Montaño, Rhodora V. AzanzaAbstractSorption mechanics of the paralytic shellfish toxins (PSTs), saxitoxin (STX) and neo-saxitoxin (neo-STX), on algal polysaccharide gels was characterized using surface chemistry models. Refined (RC), semi-refined (SRC) carrageenan and alginate showed sorption of STX and neo-STX. The sorption of PSTs on RC, SRC and alginate was affected by contact time and in part, temperature. From surface chemistry models, alginate followed a spontaneous endothermic physical monolayer sorption of STX and neo-STX. SRC and RC favoured the concurrence of physical and chemical monolayer sorption, being endothermic for SRC and exothermic for RC.
       
  • In situ and non-destructive detection of the lipid concentration of
           Scenedesmus obliquus using hyperspectral imaging technique
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Xiaoli Li, Kai Chen, Yong HeAbstractMicroalgae can be used as a raw material for biodiesel production. Monitoring the lipid accumulation process of microalgae is crucial for optimizing the microalgae culture environment and the breeding of microalgae species with a high yield of lipid. Current methods for the detection of the lipid accumulation of microalgae are tedious and require trained professionals. Thus, a fast visual and intuitive approach for the detection of the lipid concentration of microalgae with a living status is desirable for microalgae culture and bioprocess control. In this study, a fast and nondestructive method based on hyperspectral imaging (HSI) was proposed to obtain the concentration and distribution of microalgae lipids from liquid suspension culture. Several data preprocessing, regression and model development methods were tested. Savitzky-Golay data smoothing followed by a competitive adaptive reweighted sampling in a multiple linear regression model performed the best. Finally, a chemical map was provided to visualize the lipid distribution of microalgae in a suspension. The distribution map of microalgae lipids showed a dynamic process of lipid accumulation, which could be useful for the investigation of the mechanism of lipid accumulation in microalgae. Hyperspectral imaging is a promising approach to inspect the lipid concentration of microalgae in an intuitive way, which can be widely used for the screening of strains and monitoring the lipid production in microalgae industries.
       
  • Reserve, structural and extracellular polysaccharides of Chlorella
           vulgaris: A holistic approach
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Andreia S. Ferreira, Sónia S. Ferreira, Alexandra Correia, Manuel Vilanova, Tiago H. Silva, Manuel A. Coimbra, Cláudia NunesChlorella vulgaris is a green microalga approved for human consumption with high biological value due to its high protein content and polyunsaturated fatty acids composition. Moreover, this microalga is rich in starch and structural polysaccharides that could have potential to be valued as food ingredients. To fulfill this hypothesis, starch digestibility was evaluated in raw and boiled biomass, showing 43% and 71% of glucose released, respectively. The low extraction yield of starch obtained with water (13%) allowed to infer protein hindrance. This was overcome by 1 M and 4 M KOH aqueous solutions that allowed to obtain an additional 51% of starch. The final residue left showed that only 16% of total starch remained unextracted. KOH solutions allowed also to obtain galactans composed by 1,3-, 1,6- and 1,3,6-linked galactose residues. These linkages were also observed in the polysaccharides recovered from the growth medium, showing similarity between the exopolysaccharides and those present in the cell wall. The extracellular polymeric material revealed immunostimulatory effect on B lymphocytes. This opens the possibility of the use of both starch and exopolysaccharides of C. vulgaris as food ingredients.Graphical abstractUnlabelled Image
       
  • Initial evaluation of six different brown algae species as source for
           crude bioactive fucoidans
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Kaya Saskia Bittkau, Sandesh Neupane, Susanne AlbanAbstractThe fucose-containing sulfated polysaccharides (syn. fucoidans) from brown seaweeds exhibit multiple biological activities. The aim of the present study was to evaluate the suitability of crude fucoidans from six different brown algal species for further research and development. For this, fucoidans were extracted from Fucus vesiculosus (F.v.), F. serratus (F.s.), F. evanescens (F.e.), Dictyosiphon foeniculaceus (D.f.), Laminaria digitata (L.d.), and Saccharina latissima (S.l.) and compared concerning their yields, their basic characteristics, degree of sulfation (DS), molecular mass, monosaccharide composition, their contents of polyphenols, laminarin and protein as well as their radical-scavenging capacity, three exemplary bioactivities and their fluorescence intensity (FI) increasing effect on the sulfated glycan sensor Polymer-H. The activities positively correlated with the DS, fucose content and the FI of Polymer H, whereas the antioxidant capacity correlated with the coextracted polyphenols. The best predictive power for the activities showed to have the combination of FI of Polymer-H and DS, which can thus be used for an initial screening of algae extracts. D.f. turned out to be unsuitable as fucoidan source, as the extract had only a low DS (0.14) and fucose content (38.7%) as well as the weakest bioactivities. The fucoidans from S.l. and F.e., which had the fucose content, highest DS, purity and yield, exhibited the best activities and thus proved to be the fucoidans most suitable for further investigations.
       
  • Influence of sulfated polysaccharides from Ulva lactuca L. upon Xa and IIa
           coagulation factors and on venous blood clot formation
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Samara E. Reis, Rogeria Gabriela C. Andrade, Camila M. Accardo, Lenize F. Maia, Luiz F.C. Oliveira, Helena B. Nader, Jair A.K. Aguiar, Valquíria P. MedeirosThe interest in bioactive compounds from natural sources, such as marine organisms, has increased considerably in recent years. Among these compounds, sulfated polysaccharides from seaweed exhibit a broad spectrum of biological activities. Sulfated polysaccharides from green algae are still poorly investigated. For this reason, in this study, using unusual methodologies, such as extraction conditions, FACE, and RAMAN, we investigated the structural features of F50UL and F70UL sulfated polysaccharides from Ulva lactuca L. and their distinct in vitro anticoagulant and in vivo antithrombotic activities. Sulfated polysaccharides of U. lactuca were obtained by enzymatic proteolysis with ALCALASE® and fractionated by acetone precipitation. F50Ul and F70Ul sulfated polysaccharides with higher yield were partially chemically characterized by Fluorophore-assisted carbohydrate electrophoresis (FACE) and RAMAN spectroscopy analysis and submitted to an in vitro screening by APTT, PT, TT, and anti-factor Xa and IIa tests. The venae cavae ligature experimental model for the analysis of in vivo antithrombotic activity of F50Ul and F70Ul sulfated polysaccharides were also performed. The U. lactuca L. sulfated polysaccharides characterization by FACE and RAMAN showed a typical ulvans structure that contains as principal component rhamnose, but other monosaccharides (uronic acid, glucose, and galactose) are present. F50Ul (0.1–1.0 μg/μl) showed anticoagulant activity in vitro. However, F70Ul that has a similar composition did not present these effects. Also, only F50Ul sulfated polysaccharides (≥5 μg/g) showed a great in vivo antithrombotic concentration-dependent and time-dependent activity. In summary, we demonstrate the use of unusual extraction and characterization analysis procedures for U. lactuca L. sulfated polysaccharides and the ability of F50Ul to reduce the weight of thrombus in rats probably by the association with factors Xa and IIa inhibition. These results provide strong evidence of the anticoagulant potential of these sulfated polysaccharides isolated from Ulva lactuca L.Graphical abstractUnlabelled Image
       
  • Volatile compounds of six species of edible seaweed: A review
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Elena Garicano Vilar, Maurice G. O'Sullivan, Joseph P. Kerry, Kieran N. KilcawleyAbstractSeaweeds are widely distributed throughout the world. Many seaweeds are of commercial importance with some consumed directly or used as an ingredient as they have functional, nutritional and/or organoleptic properties. Consumer acceptance of food is closely related to its sensory properties, of which flavor is of prime importance. A significant contributor to flavor is the aromatic volatile components present. This review focusses on the volatile components identified in commercially important edible macroalgae species consisting of four brown (Himanthalia elongata, Laminaria spp. including L. ochroleuca, and Undaria pinnatifida) and two red species (Porphyra umbilicalis and Palmaria palmata). In excess of 200 volatile compounds have been identified consisting of hydrocarbons, alcohols, aldehydes, ketones, acids, esters, furans, phenols and sulfur- containing compounds, among others present in minor quantities. The extraction/concentration conditions, chromatography and detection methodologies applied varied and impacted on the volatiles identified due to differences in their hydrophobicity, molecular weight and vapor pressure. This review highlights that considerable more information is required to identify volatile aromatic compounds in edible macroalgae and to identify those most likely to impact sensory perception. Such information could be used to aid new product development or widen applications of these seaweeds in the food or beverage sectors.
       
  • Optimization of cyanobacterial harvesting and extracellular organic matter
           removal utilizing magnetic nanoparticles and response surface methodology:
           A comparative study
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Chao Wang, Yangyang Yang, Jun Hou, Peifang Wang, Lingzhan Miao, Xun Wang, Laodong GuoImprovements in the microalgal harvesting efficiency and separation processes will accelerate cost-effective biomass utilization. Magnetic harvesting is known as a low-cost and environmentally friendly downstream processing technology, but information on optimization of the harvesting procedures is rare. Here, we present optimized harvesting factors for Microcystis aeruginosa 1343 (M1) and 905 (M9) based on polyethylenimine (PEI)-coated iron oxide nanoparticles (IONPs) and response surface methodology. Four important factors including mass ratio (PEI-coated IONPs to dried cell biomass, g/g), stirring speed (rpm), stirring time (s), and adsorption time (min) were evaluated to obtain the optimal operational parameters for different types of cyanobacteria under natural environmental conditions. The maximum harvesting efficiencies for M1 and M9 were 93.3% and 97.5%, respectively; the optimal mass ratio, stirring speed, stirring time, and adsorption time were 0.14–0.18, 85–120 rpm, 70–95 s, and 5.5–7 min, respectively. Our results indicated that the mass ratio was the leading factor in algal harvesting. Changes in the number of cells bound with PEI-coated IONPs were closely related to the mass ratio, and this was confirmed via scanning electron microscopy results. Moreover, the PEI-coated IONPs were able to remove extracellular organic matter (EOM) synchronously via charge neutralization. Variations in fluorescence excitation emission spectra demonstrated an effective EOM removal. Quantitatively, over 34.97% and 45.35% of EOM in M1 and M9 were reduced, respectively, based on total organic carbon analysis. This study provides new insights into algal harvesting operations using magnetic separation technologies and provides practical guidance for performing magnetic separation under environmental conditions.Graphical abstractUnlabelled Image
       
  • Monitoring of eicosapentaenoic acid (EPA) production in the microalgae
           Nannochloropsis oceanica
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Marta Sá, Narcís Ferrer-Ledo, Rene Wijffels, João G. Crespo, Maria Barbosa, Claudia F. GalinhaWith the increase awareness for a healthier food regime and greener environmental processes, microalgae are being looked as a solution for a sustainable production of polyunsaturated fatty acids, such as omega-3 eicosapentaenoic acid (EPA). Nannochloropsis oceanica is an oleaginous microalga, well-known for the ability of EPA accumulation, although higher lipid productivities are still required to make the process competitive. Therefore, three cultivation parameters were tested in the present work (temperature, light cycles and nitrogen supply) in order to study the EPA profile in the polar and neutral fractions of the cells. In addition, an online monitoring tool based on a fluorescence spectroscopy technique was developed with the aim of increasing process knowledge at real time. The results of this work show that nitrogen depletion induces the highest variability in EPA accumulation in the neutral fraction (triacylglycerols). However, to increase the EPA content in the polar fraction a different strategy needs to be implemented, such as decreasing the cultivation temperature or the light available per cell. Chemometric models were developed through PCA (Principal Component Analysis) and PLS (Projection to Latent Structures), using only fluorescence spectra as inputs, enabling the monitoring of EPA in both fractions separately. High explained variance was observed (above 85%) in both fractions, with R2 above 0.81 and slopes above 0.93 for both validation and training data sets. Lower values of cross-validation and prediction errors were observed (between 0.29 and 0.49% g/gDW). The results obtained show that fluorescence spectroscopy is a powerful technique for online monitoring of non-fluorophore molecules, such as EPA, in complex process like microalgae cultivation.Graphical abstractUnlabelled Image
       
  • Red luminescent solar concentrators to enhance Scenedesmus sp.
           biomass productivity
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Mohammadjavad Raeisossadati, Navid Reza Moheimani, David ParlevlietAbstractIncreasing biomass productivity of an outdoor mass microalgal culture is the main aim of any large-scale algal producer. Under nutrient enriched conditions, light is the primary limits to growth of any microalgae. This normally results in a high level of photolimitation when paddle wheel driven raceway ponds are used as no light can penetrate beyond the top few centimetres of the culture. To achieve high biomass productivity, there is a need to develop an efficient system to deliver light into the depth of microalgal cultures in raceway ponds. We investigated red luminescent solar concentrators (LSCs) in outdoor raceway ponds to downgrade the sunlight, re-emit and, deliver it into the depth of Scenedesmus sp. cultures operated at 21 cm depth. Biomass productivity of Scenedesmus sp. significantly increased by 18.5% when red LSCs were used (9.4 g m−2 d−1). Scenedesmus sp. protein (52.9% of biomass) and lipid (16.5% of biomass) contents with red LSCs were also 15% and 10% higher than those in control with no LSCs. Protein, lipid and carbohydrate productivity of Scenedesmus sp. were also improved by 35%, 20% and 16% when red LSCs used. Therefore, if the aim is biomass production for animal feed, there would be 18.5% less cultivation area for generating the same biomass productivity using red LSCs. This can lead to a significant reduction in the cost of biomass production.
       
  • Evaluating differences in growth, photosynthetic efficiency, and
           transcriptome of Asterarcys sp. SCS-1881 under autotrophic, mixotrophic,
           and heterotrophic culturing conditions
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Tao Li, Fangfang Yang, Jin Xu, Hualian Wu, Jiahao Mo, Lumei Dai, Wenzhou XiangAbstractAutotrophic microalgae can assimilate organic carbon sources for the growth of heterotrophy and mixotrophy. In particular, the physiological and biochemical response of different microalgae species on autotrophy, heterotrophy, and mixotrophy are quite different. The aim of the present study was to determine differences in growth, biochemical composition, photosynthetic characteristics, and metabolic pathway under autotrophic, heterotrophic and mixotrophic culture conditions in an oleaginous microalga, Asterarcys sp. SCS-1881. The results showed that Asterarcys sp. can use glucose for mixotrophic growth, but cannot under strict heterotrophic growth. Mixotrophic cultures can significantly increase the biomass concentration and cell count of Asterarcys sp. The microalga accumulated more protein under mixotrophic conditions, but more carbohydrates and total lipids under autotrophic conditions. The microalga under mixotrophic culture conditions showed significantly reduced pigment content, PSII activity, and photoprotective ability, but increased the activity of PSI when compared to those under autotrophic conditions. Under mixotrophic conditions, Asterarcys sp. also showed enhanced glycolysis, photosynthetic carbon fixation, and pentose phosphate pathway and thus more ATP, carbon skeleton structure, and NADPH. Additionally, the biosynthesis of triacylglycerol, carbohydrates, and pigments was reduced under mixotrophic conditions and the core protein complexes of PSI and PSII were attenuated. Similarly, photosynthetic electron transport and many other pathways related to protein synthesis were enhanced under mixotrophic conditions when compared to the microalga cultured under autotrophic conditions. These biochemical changes may work to co-operatively ensure a more efficient supply of energy and carbon skeleton for rapid growth of the microalga under mixotrophic conditions when compared to those raised under autotrophic conditions.
       
  • Pilot-scale self-cooling microalgal closed photobioreactor for biomass
           production and electricity generation
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Emeka G. Nwoba, David A. Parlevliet, Damian W. Laird, Kamal Alameh, Navid R. MoheimaniExcessive cooling and energy requirements limit microalgal culture in closed photobioreactors. Here, the thermal behavior and biological performance of a spectrally-selective insulated-glazed photovoltaic (IGP) flat panel photobioreactor capable of co-producing microalgal biomass and electricity, while eliminating the need of cooling water was evaluated. The viability of this novel system for culturing Nannochloropsis sp. was compared to flat panel photobioreactors based on passive evaporative cooling (PEC), infrared reflecting thin-film coating (IRF), and open raceway pond. Maximum temperature (33.8 ± 2.9 °C) was highest in the IRF reactor while no significant difference was seen between IGP and PEC photobioreactors. Specific growth rate and biomass productivity of Nannochloropsis sp. was similar in all closed photobioreactors; however, raceway pond showed significantly lower productivity. Algal cultures in these cultivation systems were not thermally stressed. Electricity generated from IGP photobioreactor was 2.5-fold higher than the mixing energy requirement. Experimental results demonstrate a stand-alone IGP photobioreactor co-producing algal biomass and electricity, requiring no cooling water and grid electricity for operation.Graphical abstractUnlabelled Image
       
  • Enhancing lipid productivity with novel SiO2-modified
           polytetrafluoroethylene (PTFE) membranes in a membrane photobioreactor
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Ke Ding, Nan Wang, Xiamin Huang, Chunmei Liao, Shuai Liu, Mei Yang, Yong-Zhong WangAbstractIn this study, silica (SiO2)-modified PTFE membrane was first used to investigate the biomass growth and cellular lipid accumulation of algal cells. SiO2 nanoparticles obtained via a simple sol-gel method were modified on the PTFE membrane to change the water contact angle (WCA) of the membrane surface. The PTFE membrane modified by SiO2 with a WCA of 128.5° resulted in a high biomass yield of 4.29 g/m2/day, which was increased by approximately 40% compared with the control. Then, the maximal lipid productivity, 1.97 g/m2/day, was obtained at an inlet CO2 concentration of 5% (v/v), a light intensity of 4 mW/cm2 and a gas flow rate of 40 mL/min. It was increased 0.91-fold than that of the control (1.03 g/m2/day). The biodiesel quality of the cellular lipids of algal biofilm was significantly improved. The work demonstrates that the adsorption of algal cells in a gas-liquid separator bioreactor could be enhanced by changing the hydrophobicity of the substrate membrane, resulting in an increase in the biomass and lipid productivities of the microalgal biofilm.
       
  • Acid treatment combined with high light leads to increased removal
           efficiency of Ulva prolifera
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Xuehua Liu, Li Huan, Wenhui Gu, Shan Gao, Zhenbing Zheng, Guangce WangAbstractThe attachment of Ulva prolifera to Pyropia rafts can cause severe economic losses during the cultivation of Pyropia because it can reduce the yield, harvest, and quality of the Pyropia. The existing methods for removing U. prolifera from the Pyropia raft have many limitations, such as low removal efficiency, Pyropia damage, and environmental pollution. In this study, we developed method that can effectively remove U. prolifera attached to the raft during Pyropia cultivation. After 3 h of citric acid (pH 4.0) and high light treatment (1200 μmol photons m2− s1−), followed by recovery in seawater for 24 h, the U. prolifera was completely dead, but the Pyropia was still active. We also studied the response mechanism of U. prolifera to acid and high light, and our results showed that under acidic and high light conditions, H+ may penetrate the interior of U. prolifera cells, causing obvious synergistic injury with high light to PSII in U. prolifera. The degradation of Cyt f in this process severely hindered electron transport and slightly reduced PSI activity. Acid also destroyed the U. prolifera photoprotective mechanism, as shown by the high non-photochemical quenching (NPQ) values and xanthophyll cycle pigment contents. This study provides a solid base for further research on optimizing the treatment of U. prolifera and improving its removal efficiency.
       
  • A colourimetric method for the measuring of the mass transfer kinetics of
           carbon dioxide in aqueous media
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Manuel Vicente Ibañez, Rodrigo Jorge Leonardi, Matías Nicolás Morelli, Horacio Antonio Irazoqui, Josué Miguel HeinrichAbstractThe measurement of the gas-liquid mass transfer coefficient of carbon dioxide in aqueous media is relevant in the field of phototrophic microorganism culture. Here, we present an approach that allowed the handling of a system composed of seven chemical reactions, in which the transfer process of CO2 was one of them, pursuing the objective of quantifying the rate of dissolution of carbon dioxide in a designed liquid medium. A simple methodology, involving the use of an acid-base indicator, acting as a tracer, was successfully employed. It was established, that starting from a condition distant from its unique equilibrium, through the alteration of the initial pH value of a designed arbitrary state by adding onto it exact amounts of a strong base, the incorporation of CO2, from an air current in contact with the perturbed liquid, occurred in order to restore a new balance. For each experience, achieved under the same operational conditions, it was possible to calculate nearly equal values of kinetic constants which holds information about the behaviour of the system. Collectively the results presented here suggest that this methodology could be adapted to several different systems, enlightening easier ways of incorporating the transfer kinetics of this major carbon source on the existing growth kinetic models of phototrophic microorganisms. At the same time, it highlights the fact that probably the rate-controlling step it is not the transfer reaction of CO2 by itself, as the process of hydration of CO2 is.
       
  • Design of an artificial culture medium to optimize Haslea ostrearia
           biomass and marennine production
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): R. Nghiem Xuan, I. Safitri, J.L. Mouget, J. Pruvost, V. Turpin, P. JaouenAbstractThe diatom Haslea ostrearia was first studied by Gaillon in the year 1820 because of the greening phenomenon of oysters in western France. This microalga has the capacity to produce and excrete a blue pigment, called marennine, that has antioxidant, anti-bacterial and anti-viral properties, with possible industrial applications related to aquaculture and cosmetics. However, it is difficult to produce biomass in large concentrations in photobioreactors (i.e, usually 1 kg m−3 dry weight or higher) due to stirring sensitivity, and also because diatoms have special requirements, such as a supply of silica. This work presents a design for a new, completely artificial, seawater medium named NX (i.e, Nghiem Xuan) for optimizing cultivation of the diatom H. ostrearia in photobioreactors. NX takes account of the carbon and phosphorus sources in either organic or inorganic form, and the composition of the main elements (C, H, O, N, P, S, Si). Optimization of the calcium, magnesium and iron concentrations was found to be essential in order to achieve the highest productivities. The resulting NX medium was validated in an airlift photobioreactor. This led to productivities of 4.9 × 108 cell L−1 (ca. 500 mg L−1 of biomass) and 15.7 mg L−1 of marennine, higher than has previously been reported in the literature.
       
  • Identification of active pathways of Chlorella protothecoides by
           elementary mode analysis integrated with fluxomic data
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Lujing Ren, Xiaoman Sun, Lihui Zhang, Quanyu Zhao, He HuangAbstractMicroalgae are bio-factories for CO2 fixation, biofuel production, and high-value added product biosynthesis and wastewater treatment. Deep understandings of the intracellular pathways, metabolic regulations and physiological responses of microalgae are critical for process optimization and strain modification. In this study, a metabolic network in small scale was reconstructed for the green microalgae, Chlorella protothecoides. The reliability of this metabolic network model was confirmed by metabolic phenotype prediction. The pathway length distribution of all the elementary modes was calculated. These elementary modes were divided into 5 groups based on their macroreactions of elementary modes. The group with a short pathway length was that of lactate production. The group with a long pathway length included biomass formation. In addition, the active pathways were identified by decomposition of the determined metabolic fluxes under three conditions from references onto elementary modes with six objective functions, maximum biomass formation, minimum norm, maximum entropy production principle, maximum activity of the shortest pathway length by linear programming, maximum activity of the shortest pathway length by quadratic programming and maximum activity of the longest pathway length by linear programming. The identified active pathways were consistent with the physiological states of microalgae. These results were helpful for exploring metabolic regulatory mechanism in microalgae.
       
  • Microalgal plastidial lysophosphatidic acid acyltransferase interacts with
           upstream glycerol-3-phosphate acyltransferase and defines its substrate
           selectivity via the two transmembrane domains
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Linfei Huang, Lihua Yu, Zhongze Li, Yanhua Li, Kang-sup Yoon, Qiang Hu, Li Yuan, Danxiang HanAbstractThe plastidial lysophosphatidic acid acyltransferase of the unicellular green alga Chlamydomonas reinhardtii (CrLPAAT1) is a key enzyme involved in triacylglycerol biosynthesis. However, research on the biochemical characteristics of CrLPAAT1 has been impeded by its membrane-bound nature. In this study, the recombinant CrLPAAT1 was purified in a soluble form and was utilized for comprehensive biochemical characterization. The recombinant CrLPAAT1 favors the conditions of pH 6.5–7.5, 30 °C and the presence of magnesium ion in vitro. Similar with the CrLPAAT1 associated with the membranes, the purified CrLPAAT1 prefers to utilize C16:0-CoA over other acyl donors, whereas it showed broader substrate selectivity than the membrane-bound enzyme. By comparing the wild-type CrLPAAT1 and a transmembrane domain-truncated enzyme, it was uncovered in this study that the two transmembrane domains of CrLPAAT1 are involved in shaping its substrate preference for C16:0-CoA. Additionally, CrLPAAT1 was found to be interacting with the water-soluble plastidial glycerol-3-phosphate acyltransferase (CrGAPTcl) via its two transmembrane domains in vitro. The interaction between CrLPAAT1 and CrGPATcl can be negatively regulated by both the acyl-CoAs and lysophosphatidic acid in a dosage-dependent manner. Such a regulation pattern may represent a novel mechanism adopted by algal cells to control lipid metabolism homeostasis under various environmental conditions.
       
  • Transcriptomic and metabolomic adaptation of Nannochloropsis gaditana
           grown under different light regimes
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Maria Patelou, Carlos Infante, Flavien Dardelle, Dörte Randewig, Evangelia D. Kouri, Michael K. Udvardi, Eleni Tsiplakou, Lalia Mantecón, Emmanouil FlemetakisAbstractOmic technologies are a major source of information in understanding the cellular processes while their employment for studying microalgal biomass and productivity is rapidly expanding. Microalgae are known for their complex cellular metabolism. Environmental conditions affect intensely both their metabolic and transcriptomic profiles, resulting in production of numerous compounds with applications in pharmaceuticals, cosmetics, nutrition and biofuel. In an attempt to detect global changes occurring during environmental light alteration, an integrated omics approach was employed while the results were evaluated using different statistical approaches. An RT-qPCR based platform was utilized for the targeted transcript profiling of Nannochloropsis gaditana genes involved in primary and secondary metabolism, while the metabolite profiles were analyzed by GC–MS and GC-FID analytical methods. The combined transcriptomic and metabolomic results revealed extensive metabolic adaptations triggered by different chromatic qualities of light. In summary, an overall induction in both transcripts and metabolites, involved mainly in amino acid metabolism, was observed under red filtered light. Blue filtered light provoked decreased carbohydrate concentration but elevated polyunsaturated fatty acids content. Moreover, green filtered light induced the lowest responses in metabolite and gene transcript levels, indicating that its photons are poorly absorbed by N. gaditana. The current work suggests that spectral light changes leading to biochemical and metabolic manipulation of microalga N. gaditana can be accomplished by light filtering of solar irradiance, a cost-effective method which could be routinely applied in large scale photobioreactor cultivating systems.
       
  • Unsterilized sewage treatment and carbohydrate accumulation in Tetradesmus
           obliquus PF3 with CO2 supplementation
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Shanshan Ma, Yanling Yu, Hao Cui, Ravi S. Yadav, Jiang Li, Yujie FengA mixed gas with 10% CO2 was supplemented in unsterilized sewage to promote Tetradesmus obliquus PF3 for sewage treatment and nutrient recovery. The sewage was purified with higher removal efficiency of COD (90 ± 3%), TN (93 ± 3%) and TP (99 ± 0%) in the unsterilized condition with 10% CO2 supplementation than that with 0.038% CO2 (air) supplementation (COD: 65 ± 2%; TN: 81 ± 1%; TP: 95 ± 0%). The coexistence of bacteria and microalgae in unsterilized sewage had a significant effect on COD removal, while microalgae played a dominant role in nutrients (N and P) removal. Quality of effluent water complied with the class I-A criteria specified in Chinese Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant. Supplementation with 10% CO2 promoted the recovery of nitrogen (84 ± 10%) and phosphorus (90 ± 9%) from sewage compared to that of 0.038% CO2 (air) supplementation (N: 58 ± 3%, P: 59 ± 4%), which is due to the improved carbon supply and more favorable pH of 6.8–7.8 adjusted by high CO2 concentration. In addition, the CO2 fixation rate reached up to 551 ± 1 mg L−1 d−1 by Tetradesmus obliquus PF3 and the carbohydrate content in the obtained biomass was as high as 60 ± 2%. This study indicates that the supplementation with 10% CO2 in unsterilized sewage water has remarkable promotion effects on wastewater treatment and nutrient recovery. Therefore, waste gas containing high concentration of CO2, such as flue gas was suggested as carbon supplementation in the algal wastewater treatment.Graphical abstractUnlabelled Image
       
  • Screening of trace metal elements for pollution tolerance of freshwater
           and marine microalgal strains: Overview and perspectives
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Carolina Chiellini, Lorenzo Guglielminetti, Laura Pistelli, Adriana CiurliAbstractMicroalgae represent a putative solution to decontaminate metal polluted aquatic sites (phycoremediation). Seven different freshwater and seawater microalgal strains (Nannochloropsis sp., Dunaliella sp., Phaeodactylum sp., Chlorella sp., Isochrysis sp., Euglena sp. and Chlorogonium sp.) were exposed to five metals (Cu, Zn, As (III), Fe and Ni) at three concentrations each, simulating highly polluted sites. The experiment was conducted for a week; the survival ability of each strain and the photosynthetic pigments content (chlorophyll a, b and carotenoids) were evaluated, together with the Optical Density of each culture, pH, growth rate and biomass. Results highlighted different resistance patterns towards metals characterizing each algal strain, and the tolerance of all the microalgal strains towards arsenite. For the first time, the metal resistance pattern of Chlorogonium sp. was evaluated. Finally, our Euglena sp. and Dunaliella sp. strains were considered among the most promising organisms for phycoremediation of freshwater and seawater polluted sites respectively.
       
  • A high-capacity gene stacking toolkit for the oleaginous microalga,
           Nannochloropsis oceanica CCMP1779
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Eric Poliner, Evan Clark, Cameron Cummings, Christoph Benning, Eva M. FarreNannochloropsis oceanica CCMP1779 is an oleaginous heterokont microalga that is particularly amenable to synthetic biology approaches. The underlying complex genetic engineering often requires the expression of multiple transgenes (gene stacking). We integrated several techniques into a vector toolkit for multi-gene expression, including: multiple resistance marker genes, bidirectional promoters, and assembly of multiple expression cassettes into a single vector. We developed a series of gateway entry and destination vectors for assembly of two bidirectional promoter expression cassettes, which facilitates combinatorial high-capacity gene stacking. Several endogenous bidirectional promoters were demonstrated to be effective for driving transgene expression, with a dual-luciferase reporter system used to monitor transgene expression under different environmental conditions. The bidirectional promoter between the nitrate reductase and the nitrate transporter genes drives nitrogen source dependent transcription, enabling conditional transgene expression. Lethal concentrations of the antibiotics, Blasticidin, G418, and Nourseothricin, were determined and the corresponding marker genes used for genomic transformation selection.Graphical abstractGraphical abstract for this article
       
  • Co-culture of Chlorella and wastewater-borne bacteria in vinegar
           production wastewater: Enhancement of nutrients removal and influence of
           algal biomass generation
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Shuhao Huo, Miao Kong, Feifei Zhu, Jingya Qian, Daming Huang, Paul Chen, Roger RuanAbstractVinegar is an important seasoning and its annual output continues to increase in China. Vinegar production is accompanied by a large amount of wastewater which contains many nutrients, including acetic acid, nitrogen and phosphorus. In this study nutrients removal during the co-culture of Chlorella and wastewater-borne bacteria (Bacillus firmus and Beijerinckia fluminensis), as well as Chlorella biomass accumulation, pigment and lipid production in vinegar production wastewater were investigated. The removal rates for chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) were significantly improved after the addition of the bacteria. At the end of the cultivation, the highest COD, TN and TP removal rates were improved by 22.1%, 20.0%, and 18.1%, respectively, compared with the control group without adding bacteria. The mean growth rates of the algae in most goups decreased slightly during the co-culture with the bacteria. The wastewater-borne bacteria Beijerinckia fluminensis effectively enhanced the pigment content of Chlorella sp. The chlorophyll a, b, and carotenoids concentrations were increased by>35.7%, 20.9% and 11.2%, respectively. This study demonstrated an efficient microalgae and wastewater-borne bacteria co-culture system that can be potentially used for vinegar production wastewater treatment and also the recovery of high-value byproducts of algal pigment may offset the decrease in algal biomass.
       
  • Chloroplast morphogenesis in Chromochloris zofingiensis in the
           dark
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Zhao Zhang, Dongzhe Sun, Yue Zhang, Feng ChenAbstractIn the present study, chloroplasts were found to form after glucose was consumed in Chromochloris zofingiensis under heterotrophic cultivation, accompanied by a significant increase in chlorophyll and primary carotenoids. These changes conferred photosynthetic ability to heterotrophic cells. Meanwhile, both fatty acid and starch were catabolized to provide carbon and energy for cellular metabolism. A comparative transcriptome analysis showed that the expression of genes encoding photosynthetic proteins, as well as enzymes involved in chlorophyll and carotenoid biosynthesis were significantly up-regulated after glucose was consumed. At the same time, genes involved in fatty acid and starch biosynthesis were down-regulated, while those involved in the degradation of these storage molecules were up-regulated. Further investigation by means of enrichment analysis and gene co-expression network analysis revealed that the cells may control the above intracellular changes by directly regulating the expression levels of constitutively photomorphogenic 1, related transcription factors and the peroxisome proliferator-activated receptor signaling pathway. This work, for the first time, highlights the phenomenon of chloroplast morphogenesis in Chromochloris zofingiensis under dark conditions, and suggests possible regulatory mechanisms.
       
  • Bioprospecting and LED-based spectral enhancement of antimicrobial
           activity of microalgae isolated from the west of Ireland
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Dónal Mc Gee, Lorraine Archer, Thomas J. Smyth, Gerard T.A. Fleming, Nicolas TouzetAbstractAntimicrobial screening programmes have shown that microalgae constitute a rich source of secondary metabolites exhibiting antimicrobial activity against human and aquaculture pathogens. In this study, extracts from 80 newly isolated marine and freshwater microalgae strains were tested for antimicrobial activity against 6 pathogens (Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, Enterococcus faecalis, Staphylococcus aureus and Candida albicans). Principal Component Analysis and Hierarchical Clustering analyses (PCA-HC) of 4320 disc diffusion inhibition zones defined three main groups comprising strains with polar fractions inhibiting gram-positive bacteria, strains which exhibited broad spectrum activity and strains with non-polar fractions inhibiting gram-positive bacteria and C. albicans. Minimum Inhibitory Concentration (MIC) values were determined for 23 promising strains, which returned an activity threshold ≥15 mm inhibition zone diameter by disc diffusion method for at least one pathogen. The relationship between spectral quality and antimicrobial activity was further investigated for 5 promising strains (diatom Stauroneis sp. LACW_24, haptophyte Prymnesium sp. DMGCW_41, and chlorophytes cf. Chlorococcum sp. DMGCW_43, cf. Micractinium sp. LACW_01 and Tetraselmis sp. LACW_06), indicating a significantly higher bioactivity under blue light for the chlorophytes and red light for the diatom Stauroneis sp. LACW_24. Polar fractions from cf. Chlorococcum sp. DMGCW_43 and Stauroneis sp. LACW_24 possessed broad spectrum antibacterial activity with MIC values of 157 μg/mL and 875 μg/mL against P. aeruginosa, 157 μg/mL and 1000 μg/mL against E. coli, 438 μg/mL and 875 μg/mL against B. subtilis and E. faecalis, 110 μg/mL and 219 μg/mL, against S. aureus, respectively. This screening programme has led to the identification of several strains with promising antimicrobial activity. In addition, the manipulation of LED-based spectral quality to enhance the bioactivity of antimicrobial components within several candidate strains is described for the first time.
       
  • Enzymatic synthesis and characterization of chlorophyllide derivatives as
           possible internal standards for pigment chromatographic analysis
    • Abstract: Publication date: Available online 10 December 2019Source: Algal ResearchAuthor(s): Antonio Gavalás-Olea, Noelia Sanz, Pilar Riobó, José Luis Garrido, Belén VazAbstractIn this article the chlorophyllase activity of Dunaliella salina has been employed to generate different chlorophyllide a and b esters that could potentially be used as internal standards in pigment analysis. Chlorophyllide a (8’-hydroxyoctyl) ester was selected due its adequate chromatographic and spectral properties and was fully characterized by UV-Vis, ESI-MS and NMR. An easy room temperature procedure for its synthesis is described. Attachment
       
  • The macroalgal ensemble of Golfo Nuevo (Patagonia, Argentina) as a
           potential source of valuable fatty acids for nutritional and nutraceutical
           purposes
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Fernando Gaspar Dellatorre, Marisa G. Avaro, Marta G. Commendatore, Lucas Arce, María Enriqueta Díaz de VivarAbstractThe purpose of the present work was to study lipid content and fatty acid profile in fifteen macroalgal species typical of the coastal environments of northern Patagonia, Argentina. Total lipid content was observed to range between 2 and 12% of dry biomass, reaching an average of 7‐–12% in some abundant and globally distributed species, such as Ulva spp., Codium spp., Ceramium virgatum, and Undaria pinnatifida. Total fatty acid content was found to exceed neither 3% of dry biomass nor 30% of total lipids in any of the species studied. Polyunsaturated fatty acids (PUFAs) were dominant in all the brown species under study, particularly in the sporophyll of U. pinnatifida. Ceramium virgatum and Ulva sp. (tubular enteromorphoid thallus) were also rich in PUFAs. Essential fatty acids (linoleic acid and α-linolenic acid) and other valuable long-chain PUFAs, such as eicosapentaenoic acid, stearidonic acid, and arachidonic acid, were abundant in these species, arachidonic acid reaching up to 10 mg g−1 in U. pinnatifida sporophyll. In contrast, docosahexaenoic acid was only recorded at trace levels. Taken together, the results from the present study lead to conclude that the high levels of lipid content are indicative of potential applications of some of the most abundant species in the Patagonian coasts as biomass feedstock for lipid-based bioproducts. In line with this conclusion, eicosapentaenoic, stearidonic and arachidonic acid from the species studied could, in particular, be used for nutritional and nutraceutical purposes.
       
  • Improved production of lutein and β-carotene by thermal and light
           intensity upshifts in the marine microalga Tetraselmis sp. CTP4
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Lisa M. Schüler, Tamára Santos, Hugo Pereira, Paulo Duarte, N. Gangadhar Katkam, Cláudia Florindo, Peter S.C. Schulze, Luísa Barreira, João C.S. VarelaThe industrial microalga Tetraselmis sp. CTP4 is a promising candidate for aquaculture feed, novel food, cosmeceutical and nutraceutical due to its balanced biochemical profile. To further upgrade its biomass value, carotenogenesis was investigated by testing four environmental factors, namely temperature, light intensity, salinity and nutrient availability over different growth stages. The most important factor for carotenoid induction in this species is a sufficient supply of nitrates leading to an exponential growth of the cells. Furthermore, high temperatures of over 30 °C compared to lower temperatures (10 and 20 °C) induced the accumulation of carotenoids in this species. Remarkably, the two different branches of carotenoid synthesis were regulated depending on different light intensities. Contents of β-carotene were 3-fold higher under low light intensities (33 μmol m−2 s−1) while lutein contents increased 1.5-fold under higher light intensities (170 and 280 μmol m−2 s−1). Nevertheless, highest contents of carotenoids (8.48 ± 0.47 mg g−1 DW) were found upon a thermal upshift from 20 °C to 35 °C after only two days at a light intensity of 170 μmol m−2 s−1. Under these conditions, high contents of both lutein and β-carotene were reached accounting for 3.17 ± 0.18 and 3.21 ± 0.18 mg g−1 DW, respectively. This study indicates that Tetraselmis sp. CTP4 could be a sustainable source of lutein and β-carotene at locations where a robust, euryhaline, thermotolerant microalgal strain is required.Graphical abstractUnlabelled Image
       
  • Growth, biochemical composition and photosynthetic performance of
           Scenedesmus acuminatus under different initial sulfur supplies
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Ying Zhang, Zhenzhu Huang, Helong Zheng, Qianya Wang, Aifen LiAbstractThe effects of sulfur availability on growth, biochemical composition and photosynthetic capacity of the freshwater green microalga Scenedesmus acuminatus were investigated. Modified BG-11 media with Na2SO4 concentrations of 0.076 mM (0.25S), 0.153 mM (0.5S), 0.306 mM (control group), 0.459 mM (1.5S) and 0.612 mM (2.0S) were used to culture S. acuminatus. Sulfur repletion promoted the growth and reproduction of this species, while low sulfur supply markedly decreased the reproduction, nitrogen uptake, soluble protein and chlorophyll content, and photosynthetic activity. Elemental analysis showed that nitrogen, sulfur and carbon content per cell was significantly higher in the sulfur-limitation groups than in the control group on day 18. The metabolic response to sulfur limitation was divided into two stages: first, carbon equivalents were diverted from soluble protein to carbohydrates; then, carbohydrates were converted into neutral lipids. The total lipid content in the 0.25S and 0.5S groups reached 55.2% dry weight (DW) and 52.5% DW, respectively; neutral lipids accounted for 92.1% and 90.3% of the total lipids. Low-sulfur (0.5S) and sulfur-replete conditions both enhanced the lipid productivity. The initial sulfur level caused significant changes in the fatty acid composition of S. acuminatus. The sulfur-limited groups accumulated C16:0 and C18:1, while the sulfur-replete groups were mainly enriched in C16:0. Levels of free leucine, isoleucine, valine, lysine, glycine, alanine, aspartic acid and proline were closely related to the initial sulfur concentration. Changes in free phenylalanine, tryptophan, threonine and serine were due more to the duration of culturing. The results of this study will be useful as a reference for regulation of the initial sulfur supply to enhance lipid productivity of S. acuminatus for use in applications such as biodiesel production.
       
  • Transcriptomic and metabolic analysis of an astaxanthin-hyperproducing
           Haematococcus pluvialis mutant obtained by low-temperature plasma (LTP)
           mutagenesis under high light irradiation
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Zhu Chen, Jun Chen, Jinghua Liu, Lamei Li, Song Qin, Qing HuangHaematococcus pluvialis can accumulate sufficient levels of astaxanthin under various stress conditions. High light irradiation is essential for astaxanthin accumulation in Haematococcus pluvialis. However, a lack of genomic information limits the understanding of its physiological metabolism for high astaxanthin production. In this work, we investigated the wild-type (WT) strain and mutant strain (named as M3 which was obtained in our previous work) under high light irradiation and compared the difference in astaxanthin biosynthesis. We collected and analyzed the data of de novo transcriptome information of Haematococcus pluvialis at 24 h under high light stress. Our transcriptomic results indicated that M3 strain had higher utilization efficiency of CO2 to provide the precursors of carotenoid and fatty acid biosynthesis by increasing the expression levels of phosphoenolpyruvate carboxylase (PEPC), malate dehydrogenase (MDH), malate dehydrogenase (ME), ribulose bisphosphate carboxylase/oxygenase (Rubisco) activase (RCA) and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) while decreasing the expression levels of fructose-1, 6-bisphosphatase (FBP). The analysis of pigments, chlorophyll fluorescence and the quantitative real-time polymerase chain reaction (qRT-PCR) analysis revealed that M3 strain maintained higher photosynthetic activity by regulating chlororespiration pathway and elevating non-photosynthetic pigment (lutein, β-carotene, and astaxanthin) content to alleviate photooxidative damage. Moreover, the M3 strain showed higher fatty acid content than the WT strain. Overall, combinative analysis of de novo transcriptomic and physiological data provided information necessary for not only a better understanding of the difference in astaxanthin biosynthesis between WT and M3 strains but also the feasibility of genetic engineering of Haematococcus pluvialis in the future.Graphical abstractUnlabelled Image
       
  • Multivariate modeling for microalgae growth in outdoor photobioreactors
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): A. Mazzelli, A. Cicci, F. Di Caprio, P. Altimari, L. Toro, G. Iaquaniello, F. PagnanelliAn empirical model for prediction of microalgal growth in outdoor photobioreactors cultivation, using Principal Component Analysis (PCA) and Partial Least Squares (PLS) regression method, is implemented. Experimental data of biomass production were collected over 1 year of operation of a bubble column prototype, monitoring light and temperature and changing cultivation's conditions. PCA isolates 2 Principal Components that explain 80% of the variance and are associated with Environmental Conditions and Cultivation Conditions. Moreover, the PLS regression model showed positive results in term of responses (R2 = 0.84) and residuals, following the experimental trends of outputs as specific growth rate (μ(d−1)) and productivity calculated at Cmax (Pmax (g L−1 d−1)), giving also good prediction results in its validation test. This method could be easily used for other purpose, by changing the input values of the specific cultivation used (including CO2 uptake or wastewater dilution ratio in the culture medium), obtaining as outputs the desired variables (lipid production rate, etc.).Graphical abstractGraphical abstract for this article
       
  • Size matters – Microalgae production and nutrient removal in wastewater
           treatment high rate algal ponds of three different sizes
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Donna L. Sutherland, Jason Park, Stephan Heubeck, Peter J. Ralph, Rupert J. CraggsAbstractHigh rate algal ponds for coupled wastewater treatment and resource recovery have been the focus of much international research over the last 15 years. Microalgal biomass productivity reported in full-scale studies (1-ha or greater) have often been substantially lower than that reported from smaller scale ponds in similar climates, regardless of the season or the dominant microalgal species used. The disconnect between smaller-scale and full-scale productivity is unclear and uncertainty remains regarding the applicability of smaller scale studies to full-scale systems. In order to better understand the differences in reported productivity, the performance of three different size wastewater treatment high rate algal ponds (5 m2, 330 m2 and 1-ha) were assessed with respect to nutrient removal and microalgal productivity over three seasons. Both daily areal nutrient removal and biomass production were affected by the size of the pond. NH4-N removal via nitrification/denitrification decreased with increasing pond size, with the highest removal rate in the 5 m2 pond and the lowest in the 1-ha. Microalgal areal productivity was maximal in the 330 m2 pond, suggesting that a combination of mixing frequency and higher photosynthetic potential under low light conditions were the main drivers of enhanced productivity in this pond compared to the 5 m2 (mesocosm) and 1-ha (full-scale) ponds. The lowest daily nutrient removal and biomass production occurred in the 1-ha (full-scale) pond. Our results suggest that, based on the current design and operation of high rate algal ponds, the optimum size for maximum productivity is considerably smaller than the current full-scale systems. This has implications for commercial scale systems, with respect to capital and operational costs.
       
  • Identification of microalgae biorefinery scenarios and development of mass
           and energy balance flowsheets
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Nils Préat, Sue Ellen Taelman, Steven De Meester, Florent Allais, Jo DewulfAbstractThe notion of bioeconomy is at the basis of recent European strategies aiming at conciliating economic growth and sustainability. Consequently, extensive research has been conducted on biobased solutions such as microalgae products. Numerous initiatives to commercialize microalgae have been launched but few of them were successful. Algae biofuel is the most obvious illustration with its promises as energy supply but faces many challenges to become economically competitive. Consequently, it was recently proposed to develop microalgae biorefineries for an optimal biomass valorisation, to dilute the overall costs within a wide range of products. Herein, the energy demand for different microalgae biorefinery scenarios is investigated and critical steps identified. Each scenario is modelled using information from literature and process engineering principles. The production of lipids, proteins, methane, fertilizers and dried biomass are considered. Once defined, the scenarios are modelled and their energy inputs are discussed. We also investigate the impact of using a biobased solvent for lipid extraction instead of a conventional one. On top of that, each scenario is assessed for two cells disruption methods. In both cases, the study starts with dewatering the growth medium of the microalgae Chlorella vulgaris (240 kg DW h−1) and ends with the recovery of the products. The results vary from 20.07 to 66.53 MJ kg−1 input DW and highlight the importance of the cell disruption method in the total energy demand. While lipid extraction presents adverse impacts on proteins extraction due to solvent recovery, proteins extraction has beneficial effects on further methane production step. Our study concludes with the comparison of microalgae biomass with soy, for proteins and lipids production, and demonstrates quantitatively that microalgae-based technologies are still inefficient compared to present alternatives. This work provides quantitative numbers for further evaluation of microalgae projects considering the current stage of the technology.
       
  • Sucrose-to-ethanol microalgae-based platform using seawater
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Maria Eugenia Sanz Smachetti, Camila Denise Coronel, Graciela L. Salerno, Leonardo CurattiAbstractMicroalgal biomass is increasingly considered a promising feedstock for the production of bioethanol because it has simpler biochemical composition and structural features than plant feedstocks. However, it still requires hazardous and/or expensive acid or enzymatic saccharification processes before its conversion into ethanol by fermentation. To bypass this limitation, we identified microalgal strains that accumulate up to 10% (w/w) of sucrose, a readily fermentable sugar. Conditions were optimized to produce sucrose in half-strength seawater, as well as efficient extraction by very mild procedures, and conversion into ethanol. We present a model based on cultivation in environmental photobioreactors that predicted a productivity of 4200 L ethanol·ha−1·year−1 in raceway ponds in Brazil, approaching the average sucrose and ethanol productivity from sugarcane.
       
  • Influence of activated sludge derived-extracellular polymeric substance
           (ASD-EPS) as bio-flocculation of microalgae for biofuel recovery
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Oh Kyung Choi, Zachary Hendren, Gyu Dong Kim, Dandan Dong, Jae Woo LeeMicroalgae have great potential as an alternative feedstock for high-valued biofuel due to rapid growth and high lipid content. However, the harvesting process, which usually accounts for about 20–30% of total production cost, is a bottleneck in microalgal biofuel technology. This study characterizes the bio-flocculants potential of activated sludge derived-extracellular polymeric substance (ASD-EPS) for microalgae harvesting. The efficiency of two physical (thermal, sonication) and one chemical (NaOH) extracted EPS was compared to a control (i.e., without flocculant). The enhancement of flocculation activity of microalgae is closely related to the carbohydrate concentration of EPS. Thermal extracted EPS contains the highest carbohydrate and protein concentration. In contrast, the chemical protocol led to the extraction of a large amount of inorganic matter, and reduction in the lipid composition of the microalgal cell membrane. Thermal extraction is the most suitable protocol with the highest biomass (microalgae) recovery of up to 87.24% and is least harmful to the lipid composition of the cell membrane. Among the tested three algae strains, Chlorellavulgaris is an ideal candidate showing high flocculation activity with ASD-EPS and large lipid production.Graphical abstractUnlabelled Image
       
  • Utilization of enzymatic cell disruption hydrolysate of Chlorella
           pyrenoidosa as potential carbon source in algae mixotrophic cultivation
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Jianzhi Zhang, Yongjin He, Mingfang Luo, Feng ChenMicroalgae are promising feedstocks for nutraceutical, feed supplement or fuels, due to their various valuable chemical compositions. Downstream processes for bio-products extraction consist several steps whereof cell disruption is the most crucial part. Generally, the hydrolysate after enzymatic cell disruption is rich in sugar, protein and other nutrients. In this study, the collected hydrolysate of Chlorella pyrenoidosa biomass disrupted by cellulase was further reused as carbon source to cultivate six microalgae species mixotrophically. When using hydrolysate as carbon source, the six microalgae species could obtain biomass productivities of 0.40–0.71 g/L·d, better yields (biomass/reducing sugar) of 0.36–0.95 g/g with relative high protein (32.30–42.16% DCW, dry cell weight) and lipid (16.89–23.65% DCW) contents. Then the fatty acid and protein profiles were further investigated. In particular, the obtained comparable or lower degrees of unsaturation for lipid were favorable for biodiesel, meanwhile the first limiting essential amino acid in most of the test strains increased making them suitable as protein nutrient. This study pointed to a feasible cost reducing process for waste utilization in microalgae production.Graphical abstractUnlabelled Image
       
  • Microbial composition and photosynthesis in Antarctic snow algae
           communities: Integrating metabarcoding and pulse amplitude modulation
           fluorometry
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Daniela F. Soto, Romina Fuentes, Pirjo Huovinen, Iván GómezAbstractAntarctic snow microbial communities are complex biomes formed by different groups of microorganisms that include algae, bacteria, fungi, and archaea. During spring-summer season, abundant microalgae generate red, orange, pink, green and even yellow patches of snow. The presence of microalgae in snow ecosystems is pivotal for carbon fixation and has the potential to decrease snow albedo. Up to now, the relationship between microorganism diversity and functionality in these ecosystems in Maritime Antarctica is not well understood. In the present study, the microbial composition of different types of colored snow was determined by metabarcoding at Fildes Peninsula, King George Island (Maritime Antarctica). Additionally, light use characteristics were assessed to gain insights into the photosynthetic functionality of different algal groups causing snow blooms. Results from this study indicated that green algae of the Trebouxiophyceae and Chlorophyceae classes dominated the eukaryotes. A high abundance of Stramenopiles was also detected. Besides these findings, Principal Component Analysis was employed, revealing taxonomic distance among sampling sites. Bacteroidetes and Proteobacteria were found to be the most abundant groups in the bacterial communities with an absence of taxonomic distance among sampling sites. However, the presence of Flavobacteria and γ-Proteobacteria varied among samples. Photosynthetic parameters determined for dominating algae within the blooms were dependent on the sites and snow colors. All in all, these results show that snow algae blooms at Fildes Peninsula represent a mixture of algal species with different light requirements.
       
  • Rapid in situ measurements of algal cell concentrations using an
           
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): Jing-Yan Liu, Li-Hua Zeng, Zhen-Hui Ren, Tie-Min Du, Xuan LiuAbstractAccurate measurements of the algal cell concentration are very important in microalgae culturing and ecological monitoring. To realize an automatic, in situ measurement of the cell concentration of microalgae and to reduce the measurement cost, a detection method combining single-excitation fluorescence spectroscopy and an artificial neural network (ANN) was developed to monitor the cell concentrations of Chlamydomonas reinhardtii in the range of 2 × 105 to 6.4 × 106 mL−1 cells mL−1. Using a 470 nm wavelength light emitting diode (LED) as a light source, samples with different concentrations of Chlamydomonas reinhardtii were electronically excited. The measured fluorescence emission spectra were used as input, and the algal cell concentration was the output. Because there is a nonlinear relationship between the input and the output, a Back Propagation Neural Network Model Optimized by Genetic Algorithms (GA-BP) was established to predict the cell concentration. Then the model was validated by using samples from different growth batches. In addition, the GA-BP model was compared with the existing algae cell concentration detection methods (Back Propagation Artificial Neural Network), and it was found that the GA-BP model was more accurate. Moreover, the equipment used for this method is simple and easy to carry and install. The combination of single-excitation fluorescence spectrometry and an artificial neural network provides a feasible and cost-effective tool for algal cell concentration monitoring.
       
  • Obtaining highly pure EPA-rich lipids from dry and wet Nannochloropsis
           gaditana microalgal biomass using ethanol, hexane and acetone
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): María J. Jiménez Callejón, Alfonso Robles Medina, María D. Macías Sánchez, Luis Esteban Cerdán, Pedro A. González Moreno, Elvira Navarro López, Estrella Hita Peña, Emilio Molina GrimaAbstractSaponifiable lipids (SLs), rich in eicosapentaenoic acid (EPA), were extracted and purified from Nannochloropsis gaditana biomass. Firstly, the SLs were extracted using ethanol (96% v/v). The influence of the following operational variables was studied: water content of the wet biomass, solvent/biomass ratio, homogenization pressure and temperature. SL yields of 92–99 wt% and 80–90 wt% were achieved from dry and wet biomass, respectively, under various operational conditions from batches with different SL contents and lipid profiles. These SLs were extracted with only a 20–22 wt% purity, which was increased to 42% (100 wt% yield) by extracting the SLs with hexane. In this hexane extraction step, it was important to extract the SLs from a highly concentrated hydroethanolic solution. The SL purity was further increased to 95 wt% by acetone crystallization. Throughout this extraction-purification process, SLs were fractionated into neutral lipids, glycolipids and phospholipids - neutral lipids were recovered with higher yields than were glycolipids and phospholipids. The energy consumption per unit mass of extracted lipids was estimated, along with the solvent recovery, and compared for the dry and wet methods. When wet biomass was used, the presence of water significantly increased the energy required for ethanol. However, when cost and capacity of the main equipment (freeze-dryer, homogenizer and centrifuge) were considered, SL extraction from high pressure homogenized wet biomass resulted in a lower economic cost.
       
  • Charting a development path to deliver cost competitive microalgae-based
           fuels
    • Abstract: Publication date: January 2020Source: Algal Research, Volume 45Author(s): John Roles, Jennifer Yarnold, Juliane Wolf, Evan Stephens, Karen Hussey, Ben HankamerAbstractAccess to affordable and clean energy is a United Nations' Sustainable Development Goal. The prospects for cheap, reliable, renewable stationary energy and electric vehicles have rapidly improved, driven by de‑carbonisation and sustainability agendas, enhanced policy interventions and maturing technology options. In contrast, low-carbon renewable liquid fuel production systems remain critically underdeveloped amid market-distorting subsidies to fossil fuels. Advanced microalgae-based systems can deliver renewable fuels essential to meet United Nations Framework Convention on Climate Change COP 21 commitments. Here we use TELCA, an integrated triple-bottom-line Techno-Economic and Life-Cycle Analysis platform (economic - $·L−1 diesel, social – ERoEI MJ·MJ−1, environmental - GHG emissions g CO2·MJ−1), to define the role that key technology advances and policy settings can play in driving down the price of renewable microalgae-based diesel from US$11.11 gal−1 (US$2.93 L−1) to a point of cost competitiveness with fossil-based diesel US$3.00 gal−1 (US$0.79 L−1). This price reduction could be attained while simultaneously achieving an ERoEI of 4.1 and limiting GHG emissions to 21 g CO2-e MJ−1. Importantly, TELCA allows different jurisdictions to competitively adjust their policy settings to attract an expanding microalgae-based renewable fuel industry (case-study provided).
       
  • Light spectral effect on a consortium of filamentous green algae grown on
           anaerobic digestate piggery effluent (ADPE)
    • Abstract: Publication date: Available online 21 November 2019Source: Algal ResearchAuthor(s): Jason P. Webb, Mike van Keulen, Sze Ki Stephanie Wong, Emily Hamley, Emeka Nwoba, Navid R. MoheimaniAbstractThe use of LEDs for the commercial cultivation of macroalgae is becoming commonplace, as is adding value to glass structures such as green houses and aquaculture ponds via the use of transparent photovoltaic cells. The effect on photosynthesis and primary production by down regulating light to the red (600–700 nm) and blue (400–525 nm) parts of the spectrum was assessed on a consortium of two filamentous chlorophyte macroalgae species (Rhizoclonium sp. and Ulothrix sp.). The aim of the study was to determine the optimal wavelength for growth and to assess potential nutrient removal rates in anaerobic digestion piggery effluent. Under red and blue light oxygen evolution was reduced compared to the white light controls (WL = 3.490 > RL = 2.700 > BL = 0.800 mg O2 g biomass−1 h−1). Spectrum-adapted chlorophyll fluorescence results indicated that the highest rETRmax (9.080 ± 0.380 μmol electrons m−2 s−1) occurred when blue light was used. This was 10% greater than rETRmax when red light was used. Both blue and red light grown macroalgae showed significantly higher rETRmax compared to white light. Long-term adaptation to blue light yielded the highest rETRmax (5.550 ± 0.230 μmol electrons m−2 s−1), with an effective quantum yield (Fq/Fm′) of 0.75 ± 0.003. Productivity of the macroalgal consortium was greatest under white light (WL = 0.210 > RL = 0.129, BL = 0.110 g L−1 d−1); however red light yielded a three-fold increase in productivity when standardized against the irradiance received at the Light Harvesting Complex (RL = 6.45 × 10−3 > BL = 4.036 × 10−3 > RL = 2.377 × 10−3 g L−1 d−1 μmol photons m−2 s−1 (±SE)). These results indicate that red light provides the optimal light wavelength for maximum growth of the macroalgal consortium used.
       
  • Preferential production of microalgal hydrocarbon pentathiolates by the
           photoinitiated thiol-ene reaction of botryococcene
    • Abstract: Publication date: Available online 21 November 2019Source: Algal ResearchAuthor(s): Hidehisa Kawashima, Moe Saito, Makoto M. Watanabe, Masashi KijimaTo expand the applications of algal biomass materials, the reactivity of a microalgal hydrocarbon oil, botryococcene (E)-2,3,7,10,13,16,20,21-octamethyl-6,17-dimethylene-10-vinyldocosa-1,11,21-triene), was explored. Botryococcene was reacted with an excess of several alkylthiols in the presence of a photoradical initiator under UV irradiation (λ = 365 nm). In all cases, the thiol-ene reaction proceeded at the four vinylidenes positioned at C2, C6, C17, and C21 and at the C10 vinyl moiety, but the sterically hindered C11–C12 vinylene was inactive. Thus, pentathiolated botryococcenes were preferentially produced and isolated in good yields.Graphical abstractUnlabelled Image
       
 
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