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Publisher: Elsevier   (Total: 3181 journals)

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Showing 1 - 200 of 3181 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: 105, SJR: 1.462, CiteScore: 3)
Accounting Forum     Hybrid Journal   (Followers: 28, SJR: 0.932, CiteScore: 2)
Accounting, Organizations and Society     Hybrid Journal   (Followers: 42, 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: 444, 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: 3)
Acta Ecologica Sinica     Open Access   (Followers: 11, SJR: 0.18, CiteScore: 1)
Acta Histochemica     Hybrid Journal   (Followers: 5, SJR: 0.661, CiteScore: 2)
Acta Materialia     Hybrid Journal   (Followers: 320, 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 Poética     Open Access   (Followers: 4, SJR: 0.101, CiteScore: 0)
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  
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: 11, SJR: 2.611, CiteScore: 8)
Additives for Polymers     Full-text available via subscription   (Followers: 23)
Advanced Drug Delivery Reviews     Hybrid Journal   (Followers: 188, SJR: 4.09, CiteScore: 13)
Advanced Engineering Informatics     Hybrid Journal   (Followers: 12, 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: 2, SJR: 0.686, CiteScore: 2)
Advances in Cancer Research     Full-text available via subscription   (Followers: 34, 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: 10, 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: 20, 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: 15)
Advances in Developmental Biology     Full-text available via subscription   (Followers: 13)
Advances in Digestive Medicine     Open Access   (Followers: 12)
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: 44, SJR: 2.524, CiteScore: 4)
Advances in Engineering Software     Hybrid Journal   (Followers: 29, SJR: 1.159, CiteScore: 4)
Advances in Experimental Biology     Full-text available via subscription   (Followers: 8)
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: 1)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 9)
Advances in Food and Nutrition Research     Full-text available via subscription   (Followers: 67, 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: 11, SJR: 12.74, CiteScore: 13)
Advances in Geophysics     Full-text available via subscription   (Followers: 7, 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: 15, SJR: 3.027, CiteScore: 2)
Advances in Medical Sciences     Hybrid Journal   (Followers: 8, 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: 25)
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: 5, 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: 9, 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: 10)
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: 68)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 6, SJR: 0.371, CiteScore: 1)
Advances in Radiation Oncology     Open Access   (Followers: 2, 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: 6)
Advances in Space Research     Full-text available via subscription   (Followers: 424, SJR: 0.569, CiteScore: 2)
Advances in Structural Biology     Full-text available via subscription   (Followers: 5)
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: 38, 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: 54, SJR: 1.551, CiteScore: 3)
Aeolian Research     Hybrid Journal   (Followers: 6, SJR: 1.117, CiteScore: 3)
Aerospace Science and Technology     Hybrid Journal   (Followers: 385, 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: 483, 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: 45, 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: 54, 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: 66, SJR: 1.93, CiteScore: 3)
American J. of Emergency Medicine     Hybrid Journal   (Followers: 47, 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: 14, SJR: 1.524, CiteScore: 3)
American J. of Human Genetics     Hybrid Journal   (Followers: 37, 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: 36, 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: 267, SJR: 2.7, CiteScore: 4)
American J. of Ophthalmology     Hybrid Journal   (Followers: 66, 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: 28, 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: 5, 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: 211, 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: 227, 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)

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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  [3181 journals]
  • Feasibility of closing nutrient cycles from black water by
           microalgae-based technology
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Gustavo H.R. Silva, Ana Paula E. Sueitt, Sarah Haimes, Aikaterini Tripidaki, Ralph van Zwieten, Tânia V. FernandesAbstractMicroalgae can recover macronutrients and trace elements from wastewaters. The microalgae biomass can then be used as fertilizer to enrich impoverished agricultural soils by increasing the soil´s carbon content and providing essential nutrients for soil health. Using microalgae for wastewater treatment will enable the shift from linear sanitation systems to circular ones where the carbon and nutrient cycles can be closed. By using a nutrient-rich wastewater medium for microalgae cultivation, high biomass productivity and, therefore, high nutrient recovery, can be achieved. In this study, we demonstrated that Chlorella sorokiniana and Chlorococcum sp. were able to grow in and remove nitrogen and phosphorus from anaerobically-digested black water (AnBW), in a 211 L tubular photobioreactor (PBR), placed in a temperature-controlled (25 °C) glass greenhouse, under Dutch natural light conditions (5.8 to 23.3 mol photons.m−2.d-1 and 67 to 270 μmol.s-1. m−2). The microalgae productivity varied from 0.13 g DW.L-1.d-1 (autumn) to 0.36 g DW.L-1.d-1 (summer). The nitrogen and phosphorus removal rates were 28 to 62 mg.L-l.d-1 and 2.3 to 5.4 mg.L-l.d-1, respectively. Due to the insufficient light availability for the high nitrogen and phosphorus concentrations of the AnBW cultivation medium (1280 mg.L-l and 68 mg.L-l, respectively), the overall nutrient removal efficiencies remained below 50% even during the summer period when light intensity was at its highest. Partial nitrification was confirmed by the accumulation of nitrite (≥ 1000 mg NO2-N.L-l) in the PBR. These high NO2 concentrations did not, however, hinder microalgae growth. The macronutrient and trace element compositions of the dry microalgal biomass were similar to commercially available organic fertilizers, indicating a potential for soil enrichment.
       
  • Novel endogenous promoters for genetic engineering of the marine microalga
           Nannochloropsis gaditana CCMP526
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Margaret Ramarajan, Michele Fabris, Raffaela M. Abbriano, Mathieu Pernice, Peter J. RalphAbstractNannochloropsis is a marine microalga from the Eustigmatophyceae stramenopile lineage that has been studied extensively due to a broad range of industrial applications, mostly related to their oil and pigment production. However, tools to genetically engineer members of this group, and therefore further understand and maximise their industrial potential are still limited. In order to expand the potential industrial uses of this organism, several molecular tools, including gene promoters of different strength, are needed. A comprehensive and diverse set of well-characterized promoters is key to a number of genetic engineering and synthetic biology applications, such as the assembly of complex biological functions or entire metabolic pathways.In this study, we measured the promoter activity of three endogenous constitutive promoters from N. gaditana genes EPPSII (Nga02101); HSP90 (Nga00934); ATPase (Nga06354.1) in driving the expression of a Sh ble- mVenus fluorescent reporter fusion protein. Through a combined approach that includes flow cytometry, RT-qPCR and immunoblotting, we profiled the activity of these promoters at both the transcript and protein level. Two promoters HSP90 (Nga00934) and EPPSII (Nga02101) outperformed the widely used β-tubulin promoter, exhibiting 4.5 and 3.1-fold higher mVenus fluorescence, respectively. A third promoter ATPase (Nga06354.1) was also able to drive the expression of transgenes, albeit at lower levels. We show that the new promoters identified in this study are valuable tools, which can be used for genetic engineering and functional genetics studies in N. gaditana.
       
  • Functional deep eutectic solvent-based chaotic extraction of
           phycobiliprotein using microwave-assisted liquid-liquid micro-extraction
           from Spirulina (Arthrospira platensis) and its biological activity
           determination
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Senthil Kumar Rathnasamy, Devi sri Rajendran, Harish Babu Balaraman, Gayatri ViswanathanThe selective purification of phycocyanin from Spirulina was achieved using a potentail functional deep eutectic solvents (FDES). FDES were synthesized using carbohydrate glycerol as hydrogen bond acceptor and donor respectively. Thermophysical evaluation of FDES revealed a close interaction within the hydrogen bond donor and acceptor resulting in high density, refractive index and viscosity. The increase of temperature promotes relative linear reduction in values of the former two parameters and non-linear association with the viscosity. Microwave-assisted liquid-liquid microextraction favours the enrichment of phycocyanin to the top phase along with FDES. The linearity, limit of detection and level of quantification for phycocyanin was found to be 7–60, 11 and 85 μg/ml, respectively. A maximum yield 86% (w/w) was obtained at 6 min with the solid-substrate ratio of 23% (w/v) at microwave temperature of 348 K and FDES volume of 650 μl at 70% (v/v). The purity of concentrated extract was enhanced by ion exchange chromatography and the purified fractions were evaluated for antibacterial activity against Enterobacter aerogenes, Escherichia coli, Klebsiella pneumoniae, Zymomonas mobilis, Pseudomonas aeruginosa, and Bacillus cereus.Graphical abstractGraphical abstract for this article
       
  • Accumulation of cyanobacterial oxadiazine nocuolin A is enhanced by
           temperature shift during cultivation and is promoted by bacterial
           co-habitants in the culture
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Dominik Chmelík, Pavel Hrouzek, Jan Fedorko, Dai Long Vu, Petra Urajová, Jan Mareš, Jan ČervenýAbstractProper setting of cultivation conditions is essential for production of high-value compounds in microbial biotechnology. The present study characterizes photoautotrophic growth and capacity to accumulate the antiproliferative secondary metabolite Nocuolin A (NoA) in cyanobacterium Nostoc sp. CCAP 1453/38. As the cyanobacterial culture was found to be non-axenic, the bacteria accompanying the culture were characterized, then the growth demands and NoA production in the Nostoc-bacterial consortium were determined, and finally an axenic strain was prepared. For the purposes of growth characterization, the culture was maintained in a quasi-continuous regime under various light intensities, temperatures, and inorganic carbon concentrations in a small-scale laboratory photobioreactor. The maximum biomass growth rate obtained was 0.10 h−1 (doubling time Dt = 6.93 h). Following optimal growth conditions were identified: temperature of 35 °C, light intensity 600 μmol(photons) m−2 s−1, and 2500 ppm CO2 in the sparging gas. As the temperature optima for the biomass production and for NoA accumulation differed, biphasic cultivation for maximal NoA yield was designed, leading to a three times more effective cultivation procedure compared to batch culture maintained at a temperature optimal for NoA production. The increased NoA accumulation at reduced temperature that correlated with enhanced expression of NoA biosynthetic genes after the temperature shift suggested its regulation occurs at the expression level. It has further been shown that NoA production is reduced in axenic culture, which indicates that it is also triggered by presence of bacteria. This study shows an example of how a biphasic cultivation mode with different temperatures can be used in high-value compound production processes. It also brings direct evidence that cyanobacterial strain axenization can lead to a rapid decrease in production of valuable compounds and that non-axenic strains may be considered more suitable for retrieval and initial production of novel pharmaceutical leads.
       
  • Anti-inflammatory diterpenoids from the Brazilian alga Dictyota
           menstrualis
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Fábio do Nascimento Ávila, Luciana Gregório da Silva Souza, Pedro Bastos de Macedo Carneiro, Flávia Almeida Santos, Greyce Luri Sasahara, José Delano Barreto Marinho Filho, Ana Jérsia Araújo, Ayslan Batista Barros, Norberto de Kássio Vieira Monteiro, Edilberto Rocha Silveira, Otília Deusdênia Loiola PessoaAbstractThe chemical investigation of the brown alga Dictyota menstrualis provided three previously unreported prenylated guaiane diterpenes derivatives named as dictyols K, M and N (1 - 3), along with five structurally known diterpenoids (4 - 8). The structures of the new compounds, including their relative stereochemistry, were established by nuclear magnetic resonance (NMR) and high resolution mass spectrometry (HRMS) data analysis. In addition, their structures were improved by quantum mechanical calculations. Anti-inflammatory, antimicrobial and cytotoxic assays were performed with the isolated compounds, however, only the anti-inflammatory activity was particularly prominent. The cell viability effects of 1 - 8 on murine macrophage cell line (RAW 264.7) showed IC50 values ranging from 1.12 to 2.53 μM, and the inhibitory activity against the nitric oxide production over the lipopolysaccharide-stimulated RAW 264.7 cell was observed for all compounds with IC50 values ranging to 0.12 - 0.23 μM.
       
  • Screening of marine microalgae: Investigation of new exopolysaccharide
           producers
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): C. Gaignard, C. Laroche, G. Pierre, P. Dubessay, C. Delattre, C. Gardarin, P. Gourvil, I. Probert, A. Dubuffet, P. MichaudAbstractBiopolymers, such as exopolysaccharides are widely exploited by industry as hydrocolloids (gelling, thickening agents) and biological agents (anti-inflammatory, anti-parasitic, antioxidant, etc.). In this study, 166 marine microalgae and cyanobacteria species have been screened in order to identify strains producing original exopolysaccharides. This screening allowed the highlighting of 45 positive strains. In a second time, the monosaccharide compositions from 20 EPS of them were determined by GC/MS and HPAEC-PAD. The results led to a discovery of 8 new genera of microalgae producing EPS, including polymers with a very original composition like richness in GlcA. Finally, a phylogenic tree has been contructed in order to assess the link between the phylogeny of microalgae and the global composition of their exopolymers, based on data obtained in this study and from the literature.
       
  • Effect of recycling the culture medium on biodiversity and population
           dynamics of bio-contaminants in Spirulina platensis mass culture systems
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Danni Yuan, Mimi Yao, Lan Wang, Yanhua Li, Yingchun Gong, Qiang HuAbstractSpirulina (Arthrospira) is an important microalga that can generate a variety of commercial products. A semi-continuous mode of cultivation is often employed in microalgal cultivation. The traditional view, however, has been that cultures with recycled medium are more likely to be contaminated by microzooplankton, which is regarded as one of the critical problems in mass algal cultivation. In this study, the relationship between the population dynamics of contaminants and the medium conditions was investigated in Spirulina cultures. Spirulina platensis was cultivated in three groups of raceway ponds: one with fresh culture medium, one with medium that had been recycled for a month, and the third with medium recycled for six months. The results showed that totally 13 species of microzooplankton were observed by light microscopy, and 42 operational taxonomic units (OTUs) of prokaryotic contaminants were detected using amplicon sequencing. Out of all the contaminants, Brachionus plicatilis and Euplaesiobystra hypersalinica were observed to be the most harmful species in Spirulina cultures, while Proteobacteria were the most commonly found non-Cyanobacteria OTUs. On the initial day, more species of microzooplankton were introduced to the cultures that had recycled medium (9 species) than to those that had fresh medium (5 species). By the end of the cultivation, the algal biomass in the fresh medium group was the highest (2.8 g L−1), being almost 5 times higher than in the other two groups (around 0.50 g L−1). Our results proved that Spirulina can grow the best with fresh medium and that the more the culture medium is recycled, the stronger the inhibition on the growth of microalgae and microzooplankton. In order to improve large-scale Spirulina production, it is necessary to both subject the recycled medium to appropriate treatment to reduce the presence of harmful predators and to find effective ways to control contaminants.
       
  • A droplet-based gradient microfluidic to monitor and evaluate the growth
           
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Marwa Gamal Saad, Amirali Selahi, Mohamed Shafick Zoromba, Laila Mekki, Magdy El-Bana, Noura S. Dosoky, David Nobles, Hesham Mohamed ShafikAlgae are potential sources for different industrial products. However, biofuel production from algae still needs to reach valuable economical approaches. Select algae and optimize culture conditions considered main challenges for biofuel production. Traditional batch cultures' techniques are time and labor consuming. PDMS-based Microfluidics is time-and labor-saving technique with high throughput single cell analysis. We present gradient-based microfluidics as tools for studying algal growth under different cultivation conditions. Applying our device provides the opportunity to generate droplets with different concentrations of medium nutrients' in 200 s which keeps reagent and time for preparing such solutions using conventional techniques. Chlorella vulgaris was encapsulated inside uniformly droplets with different NO3−-N concentrations of 2.46, 6.69, 10.91, and 15.14 mΜ/L. separated devices were exposed to different temperatures of 20, 27, and 37 °C. The photosynthetic energy conversion for each cell per droplet was calculated. It was observed that the higher the NO3− concentration, the higher the growth kinetics. According to the presented results, the optimum nitrate and temperature conditions were 15.14 mΜ/L and 37 °C. Our device is considered the third effort for applying a gradient chip in algal biotechnology field. It is unique and simple in use with high competence results.Graphical abstractGraphical abstract for this article
       
  • Temperature dependence of the parameters of laser-induced fluorescence and
           species composition of phytoplankton: The theory and the experiments
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): S.S. Voznesenskiy, E.L. Gamayunov, A.Yu. Popik, Zh.V. Markina, T.Yu. OrlovaAbstractThe article discusses the opportunity to determine the species composition of a mixture of microalgae by using the temperature dependence of their laser-induced fluorescence (LIF). Experimental temperature dependences of fluorescence were obtained for the following microalgae: Picochlorum maculatum, Dunaliella salina, Chlorella minutissima, Tetraselmis viridis, Porphyridium purpureum, and Rhodomonas salina. It has been shown that the temperature dependence of fluorescence intensity of chlorophyll a in microalgae is reflective of the specific processes in cells of different microalgae species. A mathematical model for the temperature dependence of microalgae fluorescence and its relationship with the processes occurring in microalgae cells when heated has been formulated. The model allows determining the composition of mixtures with sufficient accuracy, as was shown experimentally on test mixtures of microalgae cultures.
       
  • Fluorescence coupled with chemometrics for simultaneous monitoring of cell
           concentration, cell viability and medium nitrate during production of
           carotenoid-rich Dunaliella salina
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Marta Sá, Joana Monte, Carla Brazinha, Claudia F. Galinha, João G. CrespoAbstractTwo-dimensional (2D) fluorescence spectroscopy was investigated as a monitoring tool for cultivation, harvesting, and effluent treatment of Dunaliella salina with high carotenoid concentration; aiming to improve the production process and minimise costs. Chemometric analysis, namely Principal Component Analysis (PCA) and Projection to Latent Structures (PLS), were used to build models for estimation of cellular concentration, cellular viability, and nitrate concentration in media. The estimations were based on fluorescence excitation-emission matrices (EEMs) acquired directly from algal suspensions. Cell concentration during cultivation and harvesting can be predicted by a single model capturing 92.0% of the variance, and with R2 of 0.92 and 0.97, for training and validation, respectively. Cell viability during harvesting by ultrafiltration was modelled with 79% of variance and R2 of 0.79 for training and 0.73 for validation. Nitrate concentration was successfully predicted during cultivation and permeate treatment using a single model with 81.8% of variance and R2 of 0.82 for training and 0.80 for validation. Therefore, this work demonstrates the strong potential of combining 2D fluorescence and chemometrics for monitoring different processes during microalgae production.
       
  • Bio-compatible flotation of Chlorella vulgaris: Study of zeta potential
           and flotation efficiency
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Christoph Matho, Karin Schwarzenberger, Kerstin Eckert, Behnam Keshavarzi, Thomas Walther, Juliane Steingroewer, Felix KrujatzThe energy-intensive dewatering of algae biomass, the first step of most downstream processes, remains one of the big challenges for economically relevant photoautotrophic bioprocesses. Due to its scalability and easy construction, froth flotation using the interactions between cells and bubbles shows considerable potential for this type of cost-efficient initial dewatering step. Comprehensive knowledge on both the physico-chemical conditions and the cellular surface properties are an important precondition to harvest cells by flotation. This study investigates the impact of changing the medium composition, specifically varying the pH and adding (bio-) collectors, on the zeta potential of Chlorella vulgaris SAG 211-1b. Decreasing the pH value from physiological to acidic conditions (pH 1–1.5) resulted in a strongly reduced cellular zeta potential. As validated by dispersed-air flotation, this yields a significantly enhanced cell recovery R > 95 %. The impact of the synthetic collector cetyltrimethylammonium bromide and the biopolymer chitosan on the cellular zeta potential and flotation performance was studied, resulting in a 3.3-fold decrease in the surfactant dose when chitosan was used . The basic mechanisms of cell-chitosan interaction were analysed in terms of particle size distribution and surface tension measurements, revealing interactions between flocculation and adsorption during the dispersed-air flotation of C.vulgarisSAG 211-1b.Graphical abstractGraphical abstract for this article
       
  • A numerical model coupling bubble flow, light transfer, cell motion and
           growth kinetics for real timescale microalgae cultivation and its
           applications in flat plate photobioreactors
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Ming-Jia Li, Zi-Xiang Tong, Zhi-Jie Zhou, Dong Huang, Rui-Long WangAbstractA comprehensive numerical model based on volume-of-fluid (VOF) is established in this paper for the simulation of multiphysical process of the microalgae cultivation in photobioreactors (PBRs). The comprehensive numerical model is composed of the following four models: (1) a free-surface lattice Boltzmann model for VOF simulations of bubble flow, (2) a discrete ordinate model for collimated light transfer, (3) a Lagrangian model for cell motion, and (4) a kinetic model for microalgae growth. A temporal extrapolation scheme is proposed first to extend the simulation in small time steps into the real timescale. The growths of microalgae in a two-dimensional flat plat PBR are then simulated by the model. The effects of the gas hold-up, bubble distribution, light intensity and light/dark history on the growth of microalgae are further studied in detail. The result showed that the average growth rate can be adopted for the whole PBR. The non-uniform distribution of bubbles attenuates the positive effects of bubbles on increasing light intensity inside the PBRs. Meanwhile, the simulation with the average flow field without fluctuations can lead to non-uniform distributions of cells and errors in prediction the microalgae growth due to the centrifugal effects. The residence time distribution (RTD) of cells in the PBR is almost uniform under the condition studied, and the simulation results with RTD are close to the results with cell tracking. Finally, an improved structure of flat plat PBRs with horizontal deflectors is proposed. The results demonstrated that the inserted deflectors can increase the gas hold-ups and the uniformity of gas distributions. These effects lead to higher light intensity in the PBR, which increases the growth rate of the microalgae.
       
  • Characterisation of bacteria from the cultures of a Chlorella strain
           isolated from textile wastewater and their growth enhancing effects on the
           axenic cultures of Chlorella vulgaris in low nutrient media
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Karen Tait, Dan A. White, Susan A. Kimmance, Glen Tarran, Paul Rooks, Mark Jones, Carole A. LlewellynAbstractThere is increasing interest in the use of microalgae grown on wastewater to provide useful metabolites. Several bacteria have been shown to affect the growth rate and quality of the algae, but it is not clear if this is specific to a particular group of bacteria or if nutrient conditions can also influence this interaction. The bacterial community associated with a freshwater Chlorella sp. isolated from open pond textile factory wastewater was characterised and a diverse group of bacteria isolated. We provide evidence that nutrient concentrations affect bacterial community composition. When grown in BG11 medium, the community was dominated by Pseudomonas sp., but when grown in Chu 10 medium (which contains lower nitrogen and phosphorus), the relative abundance of a Brevundimonas spp. increased. Several of the bacteria isolated were able to influence the growth of an axenic Chlorella vulgaris culture. The Pseudomonas sp. had a negative effect in all media tested whereas several isolates enhanced C. vulgaris growth, but only in Chu 10 medium. This supports the theory that bacterial stimulation of algal growth is not limited to species-specific interactions but is influenced by environmental conditions. In low nutrient conditions, Chlorella sp. may be increasingly dependent on bacteria for growth.
       
  • Photosynthetic electron transport transients in Chlorella
           vulgaris
    under fluctuating light
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Marlene Bonnanfant, Bruno Jesus, Jeremy Pruvost, Jean-Luc Mouget, Douglas A. CampbellAbstractChlorella sp. is both an important model for green algal photosynthesis and is produced using industrial scale photobioreactors. In photobioreactors, cells travel through steep gradients of illumination at rates determined by photobioreactor design, mixing rates, culture density and surface irradiance levels. We used non-invasive, rapid fluorescence measures to show that Chlorella vulgaris tolerates short-term exposures to super-saturating irradiance by transiently accelerating electron transport away from Photosystem II. This capacity lasts for only 10–20 s, and longer exposures to supersaturating irradiance induced down-regulation of electron transport through slowing of down-stream electron sinks, induction of non-photochemical quenching and net Photosystem II photoinactivation. Cells previously acclimated to high growth light were able to partially recover from the down regulation within 300–600 s, but cells previously acclimated to low growth light suffered more sustained down-regulation after exposure to super-saturating light. These metrics can be used to guide and constrain culture density, mixing rate and irradiance regime decisions in photobioreactors.
       
  • Effect of light quality on carotenogenic and non-carotenogenic species of
           the genus Dunaliella under nitrogen deficiency
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): S. Pereira, A. OteroAbstractChanges in growth, pigment content, and photosynthetic response under different light qualities were monitored for two species of the green alga Dunaliella: the carotenogenic D. salina Teodoresco and the non-carotenogenic D. tertiolecta Butcher. Log-phase cultures were exposed to 100% red, 100% blue, and a mix of 50% red and 50% blue at 300 μmol photon m−2 s−1. Cell density, biomass concentration, pigment content and photosynthetic efficiency were recorded during stationary phase, once nitrogen had been depleted from the culture medium. For both species biomass concentration was maximal in red-light, while the lowest biomass concentration was found with blue-light. No significant effect of light quality on cell density was observed for any of the species. The photosynthetic response was completely different between D. salina and D. tertiolecta. In D. tertiolecta nitrate starvation was accompanied by a reduction in photosynthetic efficiency and an increase in non-photochemical quenching processes, regardless of the light condition. This species activated a clear mechanism of energy dissipation, probably related to a xanthophyll cycle. On the other hand, D. salina massively accumulated secondary carotenoids as a response to the same disruptive conditions. Carotenoids protected D. salina cells mainly against blue light, where Fv/Fm remained high. In D. salina, pigment content changed with respect to light quality. Blue light enhanced total carotenoid content, but a mix of red and blue increased total carotenoid concentration in the culture, by stimulating a more balanced increase in dry weight and carotenoid accumulation. The application of specific light spectrum for the production of microalgal biomass with different carotenoid content that has a potentially different market value, is confirmed an important tool for the optimization of artificial-light microalgae cultivation systems.
       
  • Does Haematococcus pluvialis need to sleep'
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): A. Domínguez, S. Pereira, A. OteroAbstractLight intensity has been identified as one of the main factors affecting the synthesis of astaxanthin in Haematococcus pluvialis, but most experiments have been carried out under unnatural continuous light, which may constitute an additional source of stress to the cells. In order to isolate the role of light intensity and light:dark cycles in astaxanthin synthesis, H. pluvialis was cultivated in continuous light and with a circadian light:dark cycle of 12 h:12 h. Different initial cellular densities were used for both light regimes in order to establish different ratios of light per cell. Light:dark cycles produced higher cellular densities while continuous light produced faster nitrogen consumption and higher final astaxanthin concentrations. Under continuous light, Haematococcus pluvialis showed two different rates of astaxanthin accumulation: small amounts of astaxanthin were accumulated in the first 3 days of culture, while cells were still dividing, and massive accumulation of astaxanthin was triggered as a response to the cessation of cell division after nitrogen depletion. The generation of oxidative stress under continuous light could be responsible for the observed initial accumulation of astaxanthin that would be further exacerbated under nutrient limitation. The results confirm that light:dark cycles are optimal for the production of vegetative green cells of H. pluvialis, while continuous illumination might be used to accelerate astaxanthin accumulation rate once nitrogen is depleted from the culture medium.
       
  • N-terminal sequences affect expression of triterpene biosynthesis enzymes
           in Chlamydomonas chloroplasts
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Shih-Chi Hsu, Daniel R. Browne, Mehmet Tatli, Timothy P. Devarenne, David B. SternAbstractMetabolic engineering is an emerging technology to modify the biochemical properties of living cells. In microalgae, metabolic engineering has often been directed towards optimizing the production of desirable lipids or related bioproducts. Here we describe efforts to engineer the green alga Chlamydomonas reinhardtii for the production of botryococcene, a drop-in biofuel precursor. Genes encoding farnesyl diphosphate synthase (FPS) and squalene synthase-like (SSL)-1 and -3, were introduced into the chloroplast genome using biolistic transformation. Through a series of construct modifications, we identified intergenic sequences that promote expression of stable, discrete transcripts. We also found amino acids that dramatically increased the accumulation of SSL-3 when they were inserted at the N-terminal penultimate position, and similar manipulation of the N-terminal sequence of FPS appeared to improve its protein level as well. However, SSL-1 only accumulated to detectable levels when expressed as a chimera with SSL-3. In vitro assays showed that chloroplast-expressed SSL-3 was enzymatically active, but not SSL-1, although the SSL-1-SSL-3 chimeras were active when expressed in yeast. Taken together, our results suggest that the N-terminal sequence and other cellular factors are important when heterologous proteins are expressed in this model algal species.
       
  • Comparative transcriptome analysis between floating and attached Ulva
           prolifera in studying green tides in the Yellow Sea
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Yuan He, Yuan Ao, Yi Yin, Anxiang Yuan, Tuanjie Che, Lin Li, Songdong ShenAbstractUlva prolifera is the main alga resulting in “green tides”, which have occurred continually every summer in the Yellow Sea (YS) since 2007. The “green tide” disaster has caused negative impacts on both the economy and environment. The mainstream view is that the floating U. prolifera in the YS derives from attached U. prolifera of Pyropia aquaculture rafts on the Subei Shoal. In this study, we used the Illumina sequencing platform to compare the transcriptional profiles of floating U. prolifera and attached U. prolifera samples collected at the same time. A total of 278.1 million clean reads with 57.7 % GC content and 37,181 unigenes were generated from six libraries. A total of 21,475 genes were differentially expressed between the floating and attached U. prolifera samples. The expression profiles of 33 genes, which are related to the main metabolism in U. prolifera, were detected in the two samples of U. prolifera through FPKM and qRT-PCR analyses. The results showed that the expression levels of 26 of the 33 genes we studied in floating U. prolifera were higher than the levels in attached U. prolifera. This indicates that the main metabolic activities are more vigorous in floating U. prolifera than in attached U. prolifera. This finding furthers our understanding of metabolic mechanisms in U. prolifera with regard to the adaption to the marine environment and reveals the material basis of vigorous metabolic activity, which is related to U. prolifera blooms.
       
  • Predicting fecal coliform inactivation in a mixotrophic algal wastewater
           treatment system
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Srimali P. Munasinghe-Arachchige, Himali M.K. Delanka-Pedige, Isuru S.A. Abeysiriwardana-Arachchige, Yanyan Zhang, Nagamany NirmalakhandanOur previous reports have detailed the development of a pilot-scale algal wastewater treatment system (A-WWTS) utilizing a mixotrophic strain, Galdieria sulphuraria. This A-WWTS has consistently achieved discharge standards for organics and nutrients in a single step, concurrently reducing coliform bacteria to undetectable levels. Here, we present an approach to predict i) the fate of fecal coliform in this A-WWTS; and, ii) the fed-batch processing time required for a desired inactivation level. Specifically, a process model was developed to predict fecal coliform reduction under the synergistic effect of temperature, pH, and sunlight in terms of their individual first order inactivation rates. First-order temperature dependent inactivation rate at 20 °C (k20) was established as 0.05 h−1 with a temperature coefficient (θ) of 1.08. Inactivation coefficient due to the combined effects of sunlight was established as 0.647 m2/MJ. The proposed approach was validated with experimental data from five scenarios; the quality of predictions of log removals spanning over five orders of magnitude (r2 = 0.947; n = 12) was comparable to or better than those reported previously in inactivation studies. Utility value of this approach in forecasting fed-batch processing time under field conditions is illustrated.Graphical abstractGraphical abstract for this article
       
  • Cultivation and safety aspects of Arthrospira platensis (Spirulina) grown
           with struvite recovered from anaerobic digestion plant as phosphorus
           source
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Giorgos Markou, Dimitrios Arapoglou, Christos Eliopoulos, Athanasios Balafoutis, Raffaele Taddeo, Anthi Panara, Nikolaos ThomaidisAbstractIn this study, the cyanobacterium Arthrospira platensis, commonly known as Spirulina, was cultivated utilizing phosphorus in the form of struvite recovered from effluents of a biogas plant treating municipal and agro-industrial wastes. Under the specific experimental conditions, providing sterilized struvite at about 120 mg/L (or 15 mg-P/L) gave the same results in terms of biomass production and biochemical composition as the control cultures (with KH2PO4 as a P source). Struvite sterilization was found to be an important step because its original microbial load had a negative effect on the biomass production and resulted in biomass with lower value (lower protein and phycocyanin content). P from struvite was almost complete released upon adding it in the cultivation medium after 90 min, where parameters, such as medium pH, struvite particle size and medium reusing cycles had no effect on the kinetics of P release, indicating that P is almost immediately available for cell uptake. Since struvite was generated from effluents of a biogas plant treating municipal and agro-industrial wastes, the potential of its contamination with hazardous compounds was examined in order to assess the safety of the produced biomass. Unwanted compounds like heavy metals, bisphenol A (BPA), polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons (PAHs) were calculated to be at levels significantly lower than those of the maximum levels allowed in the European Union regulation for feedstuff safety, while neither veterinary drugs nor Escherichia coli were detected in the struvite. Results suggest that struvite recovered from biogas plants could be used as P source for the cultivation of A. platensis for feed or food quality.
       
  • Identification of auto-inhibitors in the reused culture media of the
           Chlorophyta Scenedesmus acuminatus
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Zhiying Lu, Jun Sha, Wenxuan Wang, Yanhua Li, Gaohong Wang, Yongsheng Chen, Qiang Hu, Xuezhi ZhangAuto-inhibition is widely observed in the microalgal media reuse, but auto-inhibitors in the reused culture media are not well understood. In the current study, microalgal media reuse experiments, target-directed organic matter separation and identification via gas chromatography-mass spectrometry (GC–MS) were conducted to elucidate the growth inhibitors in the reused media of the Chlorophyta Scenedesmus acuminatus. Results indicated growth inhibitors in the reused media belonged to small molecule dissolved organic matter that was mainly produced at the declining growth phase. Using an ultraviolet detector-guided resin separation procedure, dissolved organic matter in the reused media was partitioned into 13 fractions. Growth inhibition tests showed that inhibitors were in the fraction 8. GC–MS analysis revealed that fraction 8 contained fatty acid, phenol, alicyclic, and thioester compounds along with hexadecanoic acid and octadecanoic acid as its major components. Further experiments verified the existence of hexadecanoic acid and octadecanoic acid in the original reused media, and commercial standards also confirmed the growth inhibition to S. acuminatus by hexadecanoic acid and octadecanoic acid. This is the first study to confirm that microalgae can produce hexadecanoic acid and octadecanoic acid which inhibit their own growth. This study establishes an innovative target-directed method to fractionate, screen and identify compounds in dissolved organic matter. Meanwhile, the results of this study could be conducive to develop effective ways to reuse microalgal culture media and save water in microalgal cultivation.Graphical abstractGraphical abstract for this article
       
  • Influence of incorporated Spirulina platensis on the growth of microflora
           and physicochemical properties of ayran as a functional food
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Abuzer Çelekli, Zina Alajil Alslibi, H.üseyin BozkurtThe aim of this study was to enhance the growth and activity of probiotic bacteria (Streptococcus thermophilus, Lactobacillus delbrueckii spp. bulgaricus, Lactobacillus acidophilus, and Bifidobacterium lactis) by the addition of Spirulina platensis into ayran. The effects of S. platensis at 0 %, 0.25 %, 0.5 %, and 1 % concentrations on the growth of probiotic bacteria were studied before and after fermentation and on the 7th, 14th, and 21st days of storage. The S. platensis had a significant effect on the growth of S. thermophilus, L. delbrueckii spp. bulgaricus, L. acidophilus and B. lactis and the biochemical variables. The addition of S. platensis, significantly increased the growth of probiotics compared to the control after fermentation and within storage. Samples containing S. platensis had significantly higher titratable acidity levels compared to the control during the study period. The mixing of S. platensis at 1 % gave the highest total solid and protein content compared to the control samples. Viscosity values of samples having S. platensis decreased during storage time. The addition of algal biomass at 0.25 %, 0.5 %, and 1 % significantly decreased Hunter color parameters; L* and b* values compared to the control. Spirulina platensis has great potential for enhancing the growth of probiotic bacteria and the nutritional content of ayran.Graphical abstractGraphical abstract for this article
       
  • Construction of astaxanthin metabolic pathway in the green microalga
           Dunaliella viridis
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Bin Lin, Yulin Cui, Mingyan Yan, Yinchu Wang, Zhengquan Gao, Chunxiao Meng, Song QinAbstractDunaliella viridis is a green microalga containing β-carotene, which is the precursor of astaxanthin, the most active antioxidant in Haematococcus pluvialis. Two key enzymes of H. pluvialis, β-carotene hydroxylase (CRTR-B) and β-carotenoid ketolase (BKT), are required for converting β-carotene to astaxanthin in D. viridis via the astaxanthin biosynthetic pathway. Considering the location of β-carotene in the chloroplast of D. viridis, the two modified genes encoding BKT and CRTR-B in H. pluvialis were integrated via homologous recombination into the chloroplast genome, in this study. In the chloroplast, the homologous recombination vector pMD-bkt-crtr (16S-TrnA-atpA-bkt-crtR-B-rbcL-psbA-bar-TrnI-23S), bkt and crtR-B were regulated by the atpA promoter in a polycistron. The presence of astaxanthin in the D. viridis mutant expressing BKT and CRTR-B was verified using high performance liquid chromatography (HPLC), and the maximum content of total astaxanthin and canthaxanthin after high light induction were 77.5 ± 7.7 and 50.1 ± 0.8 μg g−1 in dry weight, respectively. Our results indicate that D. viridis can be used as a cell factory for astaxanthin production.
       
  • Combined treatment with 9-cis β-carotene and 22R-hydroxycholesterol
           augments cholesterol efflux in macrophages
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Lidor Mahler, Ayelet Harari, Dror Harats, Ami Ben-Amotz, Michael Peled, Alicia Leikin-Frenkel, Michal Kandel Kfir, Yehuda Kamari, Aviv ShaishAbstractHigh plasma levels of LDL-cholesterol play a causative role in atherogenesis. The first step in atherogenesis is characterized by oxidation of retained LDL particles in the arterial wall, and scavenger receptors-mediated entry of oxidized-LDL into macrophages, resulting in the accumulation of cholesterol within macrophages. Therefore, cholesterol efflux from macrophages to HDL particles is an essential process in inhibiting the formation of atherosclerotic plaques. Previous in-vitro experiments conducted in our laboratory, revealed that 9-cis β-carotene (9CBC) enhanced the efflux of radioactively labeled cholesterol from macrophages to HDL. However, the mechanism by which 9CBC enhances cholesterol efflux remained obscure. We found, in a controlled in-vitro assay, that treating macrophages both with the Dunaliella bardawil alga derived carotenoid 9CBC, and 22R-hydroxycholesterol (22-HC), two ligands of the nuclear receptors Retinoid X Receptor (RXR) and Liver X Receptor (LXR) respectively, resulted in a synergistically increase in fluorescently-labeled cholesterol efflux. Moreover, concurrent treatment of 9CBC with liarozole, which blocks the metabolism of Retinoic Acid (RA), increased cholesterol efflux from macrophages. This result strengthens our hypothesis that 9CBC activates the RXR nuclear receptor by its conversion to RA. Furthermore, cholesterol efflux was greater in macrophages isolated from alga Dunaliella-fed WT or apoE-/- mice compared to chow diet-fed mice. Our results suggest that simultaneous activation of nuclear receptors affects regulation of cellular cholesterol and may accelerate reverse cholesterol transport, by increasing cholesterol efflux from macrophages and thus, reducing the risk for atherogenesis.
       
  • Nitrous oxide (N2O) emissions during real domestic wastewater treatment in
           an outdoor pilot-scale high rate algae pond
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Maxence Plouviez, Paul Chambonnière, Andy Shilton, Michael A. Packer, Benoit GuieysseIn order to determine if nitrous oxide (N2O) emissions could affect the sustainability of microalgae-based pond systems, N2O emissions were recorded from an outdoor 900 L pilot high rate algal pond (HRAP) fed primary wastewater over 1 year. The HRAP was mixed using a paddle wheel and operated at a hydraulic retention time (HRT) of 7.5–10 days. Direct N2O emissions ranged from 4.1 to 6400 μg N-N2O·m−2·d−1 (median of 560 μg N-N2O·m−2·d−1, n = 28) at 10 days HRT, and 70–18300 μg N-N2O·m−2·d−1 (median of 4200 μg N-N2O·m−2·d−1, n = 22) at 7.5 days HRT. Using 25–75% of the data, we estimated that HRAPs designed for nitrogen removal operated at 7.5 days HRT (i.e. 9.5 m2·capita-1 required) would generate 12–53 g N2O·capita·yr-1 which is 4–17 fold higher than the default value of 3.2 g N2O·capita·yr-1 given by the Intergovernmental Panel on Climate Change for centralized wastewater treatment plants with controlled nitrification and denitrification steps. When indirect N2O emissions (via nitrogen discharge and ammonia volatilization) are included, a HRAP operated at 7.5 days HRT could generate total emissions equivalent to 21–138 g N2O·capita−1·yr−1. When expressed as a % of the nitrogen input load into the system, the HRAP direct emissions (i.e. 0.13–0.57%) and total (i.e. 0.23–1.5%) where within the range of 0–14.6% reported in the literature for centralized wastewater treatment.Graphical abstractGraphical abstract for this article
       
  • Fatty acid profiling of new Irish microalgal isolates producing the
           high-value metabolites EPA and DHA
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Lorraine Archer, Dónal Mc Gee, Andrea Paskuliakova, Gary R. McCoy, Thomas Smyth, Eoin Gillespie, Nicolas TouzetAbstractMicroalgae constitute a heterogeneous and diverse group of organisms capable of accumulating high-value products under specific conditions, making them promising organisms for biotechnological applications in the nutraceutical, functional food, animal feed, biofertilisation or biofuel sectors. Recent studies have shown that most regions of the world display low to very low levels of nutritional intakes of the long chain polyunsaturated omega-3 fatty acids EPA and DHA, highlighting the requirement for economically and environmentally sustainable means of raising the nutritional quality of foods and feeds.Eighty-five microalgae strains isolated from aquatic habitats in Ireland were successfully brought into culture and phototrophically grown, which was assessed for fatty acid composition using GC/MS. Hierarchical clustering grouped the strains into five assemblages based on their fatty acid profiles. Three marine strains (diatom cf. Stauroneis sp. LACW24, ochrophyte cf. Phaeothamnion sp. LACW34 and haptophyte Diacronema sp. GMC30) which could synthesise EPA and/or DHA were further studied in 15 L reactors to ascertain variation in their fatty acid profiles over a 65-day cultivation regime. The average yields of EPA were 3.9, 11.9 and 1.3 mg EPA / g DW for GMC30, LACW24 and LACW34, respectively. The average yields of DHA were 3.0 and 2.0 mg DHA / g DW for GMC30 and LACW34, respectively.The capacity of the strains to produce EPA and/or DHA, together with the fact that they have been previously shown to exhibit antioxidant activity and to contain appreciable levels of carotenoid pigments, make them potential candidates for the biorefining of high-value metabolites.
       
  • Enhanced biomass production and fatty acid accumulation in Scenedesmus sp.
           LX1 treated with 6-benzylaminopurine
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Guo-Hua Dao, Xiao-Xiong Wang, Tian-Yuan Zhang, Guang-Xue Wu, Xin-Min Zhan, Hong-Ying HuMicroalgae have great potential for use in the production of valuable products. However, the low productivity of microalgal cultures is a bottleneck that restricts their large-scale application. In this study, the effects of an artificial, synthetic plant growth-promoting substance, 6-benzylaminopurine (6-BA), on the growth characteristics and physiology of Scenedesmus sp. LX1 was investigated. The results showed that 6-BA affected microalgae growth and physiology in a dose-dependent manner; low doses promoted growth while high doses inhibited growth. At the optimum dose (0.1 mg L−1), the maximum algal density and the maximum population growth rate were increased by 20% and 52%, respectively, compared with the control. Meanwhile, the yield of fatty acid methyl esters (FAME) also increased, and their compositions were changed, which resulted in an increase in monounsaturated fatty acid content at lower doses. The rates of nitrogen and phosphorus uptake were also enhanced at low doses. The measurement of photosynthetic activity in the microalgae indicated that lower doses of 6-BA enhanced activity by increasing the amounts of chlorophyll, which promoted the growth of microalgae. Metabolic activity analysis showed that lower doses of 6-BA enhanced dehydrogenase activity and ATP accumulation in microalgal cells. Overall, this study shows that 6-BA has a high potential for use in the development efficient microalgal culture systems.Graphical abstractGraphical abstract for this article
       
  • Pilot-scale production of lutein using Chlorella vulgaris
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Dale D. McClure, Jonathan K. Nightingale, Audrey Luiz, Sachin Black, Jingyuan Zhu, John M. KavanaghAbstractLutein is a carotenoid pigment which has applications in the food and nutraceutical sectors, both for its use as a colourant and for its applications as a nutraceutical. Microalgae are a promising source of lutein, however to meet market demand there is a need to develop technologies which can used for large-scale production. The effect of process conditions at a 5 L scale were quantified, it was found that at low light intensities (160 μmol photons m−2 s−1) the measured specific lutein concentration was 7.4 ± 2.1 mg g−1 which was greater than the concentration of 3.1 ± 1.1 mg g−1 obtained at higher (440 μmol photons m−2 s−1) light intensities. Supplementation of the medium with nitrate led to significant increases in the maximum specific lutein concentration (10.4 ± 5.5 mg g−1) compared to medium without nitrate addition (4.3 ± 2.9 mg g−1). These conclusions were used to scale-up the process using 50 L bubble column photo-bioreactors, it was found that the productivity was maximised (1.6 mg L−1 day−1) using an air flow-rate of 1 vvm and 24 h lighting. Finally, it was found that the process could be operated on a semi-continuous basis for 32 days, achieving high lutein concentrations (15–20 mg L−1) with the performance of the system being consistent for this duration. Results from this work have clear application in the development of large-scale systems for the microalgal production of lutein.
       
  • The impact of light supply to moving photosynthetic biofilms
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Jérôme Grenier, Hubert Bonnefond, Filipa Lopes, Olivier BernardAbstractThe production of microalgae using biofilm-based processes is becoming popular because of their higher productivity compared to traditional culture systems. Another advantage of microalgal biofilms is the straightforward harvesting procedure achieved by scraping off the biofilm, significantly reducing the energy demand required when concentrating liquid culture. Here, a promising way to grow microalgae is explored, examining a biofilm developed on a moving conveyor belt. Algae are then successively exposed to light and dark periods as the conveyer belt rotates. A lab-scale biofilm-based reactor mimicking the light pattern of the moving system was first used to study the effect of light/dark cycles on a Chlorella autotrophica biofilm. The succession of light and dark phases (in the order of minutes) effectively dilutes the light over a given time period and mitigates over-exposure of light, which can lead to photoinhibition. When the illumination time represents one-third of the cycle period (light dilution factor of 3), the biofilm seems to deal with photoinhibition better than when the biofilm is exposed to permanent illumination. Extrapolations for a rotating conveyer belt in such conditions points out twofold productivity compared to a static biofilm exposed to continuous light. However, when the periods in the dark extend too long, respiration decreases the carbon pool, hindering the benefit of photosynthesis, and a trade-off must be achieved.
       
  • Metabolic engineering of Synechocystis sp. PCC6803 to produce
           astaxanthin
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Yaming Liu, Yulin Cui, Jun Chen, Song Qin, Gao ChenAbstractAstaxanthin is a carotenoid with wide applications because of its strong antioxidant properties. It is mainly produced from the green alga Haematococcus pluvialis, but large-scale production remains a challenge. To provide another source, here, Synechocystis sp. PCC6803 was adopted as the chassis cell, and its carotenoid biosynthesis pathway was genetically extended to produce astaxanthin. The β-carotene ketolase gene (bkt) and carotenoid hydroxylase gene (crtR-B) from H. pluvialis, which wild-type Synechocystis sp. PCC6803 lacks, were optimized based on the codon preference of Synechocystis sp. PCC6803 and heterologously expressed in that bacterium to create a strain capable of producing astaxanthin. The Synechocystis sp. PCC6803 mutant synthesized 4.81 ± 0.06 mg astaxanthin per gram of cells (dry weight) after nitrogen starvation for 14 days. More than 30% of the total astaxanthin was in the free form, and 82.61% was the strong antioxidant 3S, 3′S-astaxanthin isoform. These results show the industrial application potential of metabolically-engineered Synechocystis sp. PCC6803 for astaxanthin production.
       
  • A new approach to finding optimal centrifugation conditions for
           shear-sensitive microalgae
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): A. Molina-Miras, L. López-Rosales, M.C. Cerón-García, A. Sánchez-Mirón, F. García-Camacho, A. Contreras-Gómez, E. Molina-GrimaA study has been conducted to assess clarification efficiency and cell damage during centrifugation, and to optimize this operation for the dinoflagellate microalga Amphidinium carterae. Although cells were easily recovered from the cell suspension, cell damage was observed in some experiments once the cells had sedimented. Cell damage depends on both the residence time of the cells in the pellet and on the g-force applied. 2D Computer fluid dynamics simulations were carried out to simulate and predict microalgal cell settling times, and a dimensionless number was used to obtain an operating window (combinations of g-force and centrifugation time) for optimal centrifugation of the microalga. The approach used in this study can be extrapolated to other cells and other centrifuges.Graphical abstractGraphical abstract for this article
       
  • Cooling coil led to the collapse of N-replete Haematococcus pluvialis
           cultures by releasing lethal levels of Cu2+
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Junfeng Wang, Wen Liu, Tianzhong Liu, Qiang HuAbstractPhotobioreactors for outdoor microalgal cultivation should be equipped with temperature control devices to avoid overheating. However, it is still not clear whether the cooling devices would release poisonous levels of Cu2+ that could affect the growth of microalga. In this study, the half maximal inhibitory concentration (IC50) of Cu2+ was determined by studying the effects of Cu2+ concentrations on the growth and photosynthesis of Haematococcus. Then, the Cu2+ release dynamics were studied by soaking copper cooling coils in water for different times. The results indicated that the IC50 of Cu2+ for Haematococcus was approximately 20 μM (16.9 μM) and, above this level, the growth and photosynthesis were obviously inhibited before astaxanthin production. Meanwhile, after being soaked in water for only 10 h, the copper cooling coil released 40 μM Cu2+, which was 100% higher than the IC50 and high enough to impose severe heavy metal stress on cells. These results indicated that Haematococcus was sensitive to Cu2+. Devices made with copper or copper-containing materials could release lethal levels of Cu2+ if exposed to a liquid environment and brought into direct contact with microalgal cells. This research sheds some light on the design and operation of cooling systems for outdoor large-scale microalgal cultivations.
       
  • Application of an engineered chromatic acclimation sensor for
           red-light-regulated gene expression in cyanobacteria
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Shunichi Kobayashi, Mitsuharu Nakajima, Ryutaro Asano, Eunice A. Ferreira, Koichi Abe, Paula Tamagnini, Shota Atsumi, Koji SodeThe development of a versatile tool for the gene regulation in cyanobacteria is critical for the future realization of cyanobacterial bioprocessing. The use of chemical inducers to regulate gene expression are not practical considering their cost and technical difficulty in removing them from culture. Therefore, we have focused on a cyanobacteria-derived chromatic acclimation sensor, the green-light sensing system, CcaS/CcaR two-component system, derived from Synechocystis sp. PCC6803 (PCC6803) as a toll for genetic regulation. However, the regulation of gene expression levels by CcaS is not strict. We have previously developed a miniaturized CcaS, CcaS#11, which is a truncated CcaS showing gene induction under red-light illumination and strict repression under green-light illumination in Escherichia coli. In this study, CcaS#11 was transformed in cyanobacteria to achieve red-light-regulated gene expression in cyanobacteria. The application was first attempted in PCC6803 after knocking out genomic CcaS/CcaR system to exclude interference. The results revealed gene expression was only induced under red-light illumination and strictly repressed under green-light illumination. The red-light-regulated gene expression was also applied for a marine cyanobacteria, Synechococcus sp. NKBG15041c (NKBG15041c). In NKBG15041c, gene expression was induced under red-light illumination and strictly repressed under green-light illumination with a 2-fold higher ON/OFF ratio compared with the original CcaS/CcaR two-component system. Therefore, the constructed red-light-regulated gene expression system using CcaS#11 has a great potential as a platform technology for the further development of light-regulated bioprocesses with strict control in cyanobacteria.Graphical abstractGraphical abstract for this article
       
  • Life cycle assessment of pilot and real scale photosynthetic biogas
           upgrading units
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Ana F. Ferreira, Alma Toledo-Cervantes, Ignacio de Godos, Luísa Gouveia, Raul MunõzAbstractIn the present study, the sustainability of the simultaneously upgrading of biogas and high-value algal biomass production was evaluated in terms of energy consumption, CO2 emissions and environmental impacts. Two pilot-scale biogas upgrading units and a simulated real scale plant were considered. The study included the creation of an inventory of all sub-processes involved in the production of algal-biomass and biomethane. A comprehensive analysis using a life cycle methodology of the whole process was also conducted. The whole process was divided in three main sub-systems: the gas absorption unit (biogas upgrading), microalgae biomass production unit (HRAP, High Rate Algal Pond) and the biomass recovery unit (for its valorization). The analysis of environmental impacts was carried out for the real scale plant using the software SimaPro, considering the ReCiPe endpoint (H) and midpoint (H). For the two pilot-scale biogas upgrading, as expected, artificial illumination in the indoor HRAP was responsible for ≈ 90% of the total energy demand. For the simulated real-scale plant, the biomass recovery step (harvesting and drying processes) exhibited the highest environmental impacts, while the biogas upgrading unit showed high impacts on climate change and low impacts on fossil and water depletion.
       
  • A simple method for rapid purification of phycobiliproteins from
           Arthrospira platensis and Porphyridium cruentum biomass
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Rosaria Lauceri, Graziella Chini Zittelli, Giuseppe TorzilloMembrane chromatography was exploited to purify allophycocyanin, phycocyanin and B-phycoerythrin from aqueous extracts of fresh or freeze-dried biomass of Arthrospira platensis (Cyanobacteria) and Porphyridium cruentum (Rhodophyta). The method can be tuned to obtain products having various degree of purity and avoids expensive and time consuming column chromatography and ultrafiltration steps. A commercial polyvinylidene fluoride (PVDF) microfiltration membrane (hydrophilic and low protein binding) was used as an ammonium sulphate responsive stationary phase to carry out the purification process. Analytical grade purity was achieved for phycocyanin (purity = 4.2–4.5, yield = 75–82 %) and B-phycoerythrin (purity = 4.5–4.8, yield = 69–71 %). Good purification, even if lower than analytical grade, was achieved for allophycocyanin (purity = 3.3–3.7, yield = 42–47%).Graphical abstractGraphical abstract for this article
       
  • High methane yields in anaerobic digestion of the cyanobacterium
           Pseudanabaena sp
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Sara P. Cuellar-Bermudez, Jose Antonio Magdalena, Koenraad Muylaert, Cristina Gonzalez-FernandezAbstractMicroalgae are a novel biomass feedstock for the production of biogas through anaerobic digestion. However, anaerobic digestion of microalgal biomass often suffers from low methane yields due to their rigid cell walls. In contrast to eukaryotic microalgae, prokaryotic cyanobacteria have a weaker cell wall and might be more attractive as feedstock for anaerobic digestion. Nevertheless, feedstock biomass composition influences the anaerobic digestion process. In cyanobacteria, nitrogen is a key nutrient for which availability induces changes in the biomass composition. In this study, the cyanobacterium Pseudanabaena sp. CY14-1 was cultivated at different nitrogen concentrations (14, 42 and 56 mg N L−1) to achieve biomass with a variable carbohydrate content (61, 38 and 23% dry weight, respectively). Anaerobic digestion of these three types of Pseudanabaena sp. CY14-1 biomass was performed in batch experiments to evaluate the effect of biomass composition on methane yields. During the first days of the experiment, the methane yield of the biomass was comparable irrespective of the carbohydrate content. The final methane yield, however, was higher for the biomass with 23% carbohydrate content (251 mL CH4 g-1 CODin) than for the biomass with 38 and 61% carbohydrates (226 and 215 mL CH4 g-1 CODin, respectively). In contrast, 61% carbohydrate-rich biomass showed the highest hydrolysis constant (0.21 day-1) among the three types of Pseudanabaena sp. CY14-1 biomass. Methane yields achieved with these three biomasses are higher than those reported for some eukaryotic microalgae species, highlighting the potential of cyanobacteria as biomass feedstock for anaerobic digestion.
       
  • Proteomics analysis of lipid droplets indicates involvement of membrane
           trafficking proteins in lipid droplet breakdown in the oleaginous diatom
           Fistulifera solaris
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Tomomi Nonoyama, Daisuke Nojima, Yoshiaki Maeda, Masayoshi Noda, Tomoko Yoshino, Mitsufumi Matsumoto, Chris Bowler, Tsuyoshi TanakaAbstractMicroalgae store triacylglycerol (TAG) in a specialized intracellular compartment called the lipid droplet. Its dynamics are believed to be controlled by various lipid droplet-associated proteins, although studies of microalgal lipid droplet-associated proteins are still limited. In the present study, proteomics analysis was carried out to identify novel lipid droplet-associated protein candidates in the oleaginous marine diatom Fistulifera solaris JPCC DA0580. Lipid droplets were extracted from diatom cells, followed by washing with urea solution to decrease contaminants. Subsequently, proteins were identified from the urea-treated lipid droplet fraction. Comparisons between the present study and previous proteomic research on other microalgae revealed that the lipid droplet fraction extracted from diverse microalgae commonly contained membrane trafficking-related proteins such as vesicle coat proteins and heat shock proteins, some of which could potentially be involved in autophagy. Autophagy is known to degrade lipid droplets in other organisms (i.e. mammalian cells and yeasts), and this process is termed lipophagy. Thus, the membrane trafficking-related proteins which were detected from the proteome in this study might play a role in TAG hydrolysis via lipophagy. In order to confirm this hypothesis, we utilized inhibitors of membrane trafficking-related proteins and lipophagy. The addition of the inhibitors to F. solaris during lipid droplet breakdown suppressed TAG hydrolysis, supporting the idea that lipophagy may participate in TAG hydrolysis in F. solaris. The phenomenon was also observed in another model pennate diatom, Phaeodactylum tricornutum, implying that lipophagy-mediated lipid droplet breakdown could be a common feature, at least in pennate diatoms. These findings shed light on novel aspects of lipid metabolism in microalgae, and this can be applied to new approaches for increasing the oil productivity of biofuel production using microalgae in the future.
       
  • Evaluation of yield-predictive models of biocrude from hydrothermal
           liquefaction of microalgae
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Alejandra Palomino, Luis Carlos Montenegro-Ruíz, Rubén Darío Godoy-SilvaAbstractThe prediction capacity of published component additivity and kinetic models was analyzed for calculation of the biocrude yield of hydrothermal liquefaction of microalgae. Their advantages and limitations were identified. Likewise, the effect of reaction temperature and retention time was evaluated on the yield of the biocrude for the kinetic models for four hypothetical biomasses. From the analysis of the component additivity and kinetic models, a new quantitative model was proposed for the calculation of biocrude yield of microalgae. The new model was tested with large numbers of experimental data published over a wide range of temperatures (200–400 °C), retention times (1–120 min) and chemical composition of microalgae (0.0–66% lipids, 9–75% proteins, 5–64% carbohydrates, in dry basis). The predictive capacity of the new model was compared with component additivity and kinetic models. Results show that the model captures better the trend of the experimental data. This model predicted 45% of the biocrude yields published within the standard deviation zone ± 5% and 78% of the total data was within the zone of standard deviation ± 10%. The combined model predicts yields of up to 60% for lipid-rich biomasses and shows a better linear distribution between experimental and predicted yields than any other currently available model.
       
  • A comprehensive review on microalgal harvesting strategies: Current status
           and future prospects
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Madonna Roy, Kaustubha MohantyMicroalgae are considered as a potential and sustainable feedstock for the production of biofuels, fine chemicals, nutraceuticals, and cosmetics. This is accredited to their high lipid and carbohydrate content, fast growth and rapid CO2 sequestration ability. However, large volumes of feedstock are required to extract and process biochemicals from microalgal biomass due to the small biomass to liquid ratio. This produces substantial challenges in attaining a sustainable energy balance in microalgae-based products process operations. Additionally, the small size of microalgal cells along with their negatively charged cell surface and cell density similar to the growth medium produces challenges in microalgae harvesting. The high cost associated with microalgae harvesting is a major bottleneck for commercialization of algae-based industrial products. Hence, microalgae harvesting is recognized as an area that needs to be explored and developed. This article aims to collate and present an overview of current harvesting strategies such as physical, chemical, biological, electrical and magnetic methods along with their future prospects. This review also highlights the evolution of microalgal harvesting and elucidates the fundamental phenomena of each technology in relation to key physical parameters such as morphology, size, density and surface charge. Besides throwing widespread light on various harvesting methods, this review article has also presented their advantages and disadvantages. Life cycle assessment (LCA) and technoeconomic analysis (TEA) was reviewed to assess the feasibility of various harvesting system for commercial application based on the environmental and technoeconomic impacts. Hence, the vital proposals provided in this review article would undeniably pave the way for choosing the appropriate harvesting strategy.Graphical abstractGraphical abstract for this article
       
  • Optimization of algae production on urine
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Kanjana Tuantet, Hardy Temmink, Grietje Zeeman, René H. Wijffels, Cees J.N. Buisman, Marcel JanssenAbstractUrine is a potential source of nutrients to grow microalgal biomass to be re-used as fertilizer and soil conditioner. In this study the impact of photobioreactor dilution rate on microalgae productivity and photosynthetic efficiency was assessed and used to determine operating conditions to reach both full nitrogen removal from urine and high biomass productivity. In addition, the possibility to work under day/night cycling was tested. To this end, the microalga Chlorella sorokiniana was grown on artificial urine and real human urine in bench-scale panel photobioreactors with short optical paths.At a light intensity of 1530 μmol⋅ m−2⋅s-1 photobioreactor productivity and photosynthetic efficiency was demonstrated to be maximal at reactor dilution rates between 0.10 and 0.15 h-1. A biomass yield of 1 g dry matter per mol of PAR photons was achieved. Biomass concentration, and accordingly nutrient removal efficiency, decreased at increasing reactor dilution rate. The experimental results could be reproduced by model simulations. These simulations allowed to demonstrate that the system must be operated at a dilution rate of less than 0.01 h-1 in order to reach complete nitrogen removal. In that scenario more than half of the potential biomass productivity is lost due to severe self-shading within the algal culture. Experiments with real human urine illustrated the problem of incomplete nitrogen removal and ammonium inhibition of growth at too high dilution rates. It is therefore suggested to apply an optimized pre-dilution of pure urine prior to treatment in a photobioreactor.Experiments under day-night cycles demonstrated that microalgal cultures quickly acclimate to such variable light conditions. Additional model simulations illustrated that a phototrophic system is most effective when diluted urine is fed to the photobioreactor during day time only. In that situation the lowest nitrogen concentration in the effluent can be reached at a maximal areal removal rate and photosynthetic efficiency.
       
  • Membrane technologies for microalgal cultivation and dewatering: Recent
           progress and challenges
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Meijia Zhang, Lishan Yao, Esmat Maleki, Bao-Qiang Liao, Hongjun LinAbstractCultivation, harvest, and dewatering of microalgae have many challenges due to the low biomass concentration (0.5–1 g/L) in open ponds and conventionally closed photobioreactors. Membrane technologies have been widely used in various stages of microalgal biomass production and concentration for process intensification. This paper provides a state-of-the-art review of recent progress (2014-present) in the application of membrane technology in microalgae cultivation, harvest, and dewatering. The application of membranes in microalgae cultivation and factors that affect microalgae growth are systematically reviewed and discussed. Also, membrane filtration processes for microalgae dewatering and major factors affecting the efficiency of microalgal dewatering are summarized and discussed. Moreover, the economics of membrane filtration, research gaps, and membrane fouling issues in microalgal systems are identified and discussed. Membrane technologies have shown a bright future in microalgal biorefinery.
       
  • Design and testing of an externally-coupled planar waveguide
           photobioreactor
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Christopher Salmean, Sofia Bonilla, Yaldah Azimi, J. Stewart Aitchison, D. Grant AllenAbstractWaveguides can be used to deliver light deep into algal photobioreactors, allowing the growth of algal biofilms with high areal yield. A current drawback of these reactors is their dependency upon artificial illumination. A more practical approach would be to use direct sunlight to illuminate the waveguide photobioreactor. In this paper a novel optical system is designed to grow algal biofilm using waveguides illuminated with external light using 3D-printed paraboloidal mirrors. It was found that the polygonal approximation of a compound parabolic trough was an effective mechanism for focusing external natural light, which could be constructed easily. It is also demonstrated that algae biofilm biomass productivity on the waveguide increases by a factor of 2.5 when operated in conjunction with mirrored troughs.
       
  • Screening of microalgae and LED grow light spectra for effective removal
           of dissolved nutrients from cold-water recirculating aquaculture system
           (RAS) wastewater
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Čedomir Stevčić, Katja Pulkkinen, Juhani PirhonenPopularity of recirculating aquaculture systems (RAS) is increasing. Because of the high water recirculation rate, dissolved nutrients originating from fish feed are concentrated enough in RAS wastewater (WW) to enable growth of primary producers, e.g. microalgae. This study evaluated nitrate-nitrogen (NO3-N) and phosphate-phosphorus (PO4-P) removal efficiency of ten temperate zone freshwater microalgae species during their exponential growth phase in unfiltered RAS WW at 17 ± 0.5 °C. Growth and nutrient uptake efficiency of six green and four non-green microalgae strains were compared between WW and reference growth medium in batch monocultures. The effect of three different LED grow light spectra on growth and nutrient uptake efficiency were compared for four green microalgae in WW. The specific growth rate (SGR, 0.5-0.8 d−1) and removal of NO3-N (N%, 57–96%) and PO4-P (P%, 78–94%) of green microalgae in WW in 4 days were comparable to the results obtained in the reference medium (SGR, 0.6-0.9 d−1, N%, 59–99%; P%, 86–99%). In contrast, non-green microalgae had negligible growth (SGR, from -0.1 to 0.2 d−1) and poor nutrient removal (N%, 1–29%; P%, 0–34%) in both growth media after 9 days. The three LED spectra did not differ on their effect on growth and nutrient removal of three green microalgae in WW after 4 days, while the fourth tested species, Haematoccocus pluvialis, had its highest nutrient removal after 8 days under a specific LED spectrum. Current results show that RAS WW supports well green microalgae growth in batch cultures in temperatures common in Nordic RAS and that continuous spectrum LED grow lights can induce high removal of dissolved nutrients. Our findings lend support to the concept of using temperate zone microalgae for nutrient removal and recycling from RAS WW.Graphical abstractGraphical abstract for this article
       
  • Nitrogen supplemented by symbiotic Rhizobium stimulates fatty-acid
           oxidation in Chlorella variabilis
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Cong Fei, Tong Wang, Abeselom Woldemicael, Meilin He, Shanmei Zou, Changhai WangAbstractLarge-scale cultivation of microalgae benefits from co-cultivation with model growth-promoting microorganisms to increase algal biomass and lipids production. Nevertheless, the effect of natural symbiotic bacteria on microalgae cultivation and lipid production is still unclear. Here, the effects of nitrogen-fixing, symbiotic Rhizobium on nitrogen content and algal growth, lipid accumulation, and gene expression were investigated in the green microalga Chlorella variabilis. The results demonstrated that compared to axenic C. variabilis cultures, the bacterial-derived nitrogen supply and algal growth were enhanced by 32.8% and 27% in cocultures, respectively. Transcriptome analyses revealed that C. variabilis growing with R. radiobacter TH729 upregulated genes involved in fatty acid oxidation and downregulated genes related to nitrogen metabolism. Our findings indicated that bacterial fixed nitrogen reduces lipid accumulation in microalgae, which is not beneficial for biodiesel production. Further studies on the effects of other bacteria on microalgae are needed to assess most optimal practices for biodiesel production.
       
  • Nitrogen-fixer enhances lipid yields in algal polycultures
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Maria Stockenreiter, Elena LitchmanAbstractCurrent algal biomass research still focuses mainly on identifying and growing monocultures that produce high amounts of lipids or other target compounds. However, monocultures might have a lower efficiency of utilizing resources, due to their limited physiological resource use possibilities, compared to algal polycultures. Recent studies showed that species diversity enhances the lipid production of microalgae. To identify the general patterns of enhanced lipid production in diverse microalgal communities it is essential to investigate links between resource use complementarity and the corresponding lipid production.Cyanobacteria and Chlorophyta are highly differentiated in their light spectrum utilization and nutrient requirements, e.g., some Cyanobacteria species can fix atmospheric nitrogen. To investigate whether these two groups are complementary in terms of optimizing biomass and neutral lipid production, we compared the growth of several species of Cyanobacteria and Chlorophyta in monocultures and polycultures consisting of species from both groups. Results show that lipid production increases with increasing functional diversity and that using just two different functional groups of microalgae provides a positive biodiversity effect. Lipid yields were particularly enhanced by the presence of a nitrogen-fixing cyanobacterium. Additionally, lipid yields were decoupled from higher biomass production in diverse communities. In summary, our results show that the enhancement of lipid production due to biodiversity can be achieved through combining just two physiologically different taxonomic groups and including a nitrogen fixer. This may make achieving the benefits of biodiversity in algal mass cultivation more straightforward.
       
  • Growth performance and nutrient removal of a Chlorella vulgaris-Rhizobium
           sp. co-culture during mixotrophic feed-batch cultivation in synthetic
           wastewater
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Lorenza Ferro, Zivan Gojkovic, Raul Muñoz, Christiane FunkAbstractThe subarctic green algal strain Chlorella vulgaris 13-1, newly isolated from Northern Sweden, and its co-occurring bacterium Rhizobium sp. were tested for their ability to produce valuable biomass and remove nutrients from synthetic wastewater during mixotrophic feed-batch cultivation at multiple hydraulic retention times (HRTs = 7, 5 and 3 days). The algal-bacterial co-culture showed better performance compared to the corresponding axenic cultures (HRT = 7 days), with a biomass concentration of 0.63 ± 0.03 g/L and removal rates of 49.5 ± 6.1% TOC, 55.7 ± 8.04% TN and 95.6 ± 3.6% TP at steady-state. Culture stability and a high nutrient removal capacity were recorded in the algal-bacterial co-culture even at HRTs of 5 and 3 days. Interestingly, reducing the HRT from 7 to 5 days resulted in a higher lipid content of the biomass, further reduction of the HRT to 3 days enhanced both daily biomass productivity (1.03 g/L/day) and nutrient assimilation. Mixotrophic co-cultivation of C. vulgaris-Rhizobium sp. can successfully be applied for wastewater reclamation in continuous mode at HRT of 3–7 days, and thus is suitable for both summer and winter conditions in Nordic countries.
       
  • Experimental evaluation of the effect of water velocity on the development
           of string-attached kelp seedlings (Laminariales) with implications for
           hatchery and nursery production
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): César Peteiro, Gorka Bidegain, Noemí SánchezAbstractKelp sea farming is performed using seedlings (early stage of sporophyte development) attached to string, known as seedling string, which are produced from an indoor culture under controlled environmental conditions. However, very little is known about the influence of water movement and the optimal growth level of early kelp sporophytes on string. Thus, the present study evaluated the development of string-attached kelp seedlings (Undaria pinnatifida) simultaneously exposed to simulated seawater velocities in an indoor tank. The experiment was conducted using string that had seedlings approximately 2 mm in length, whose growth was measured after 28 and 56 days of culture. Seawater velocity level was found to significantly influence both the rates of increase in total biomass (dry weight) and in length of kelp seedlings on string. Seedling growth rates increased up to a water velocity range of 15.8–17.1 cm s−1 beyond which it declined. This pattern is similar for the two time periods explored during the experiment, although both growth rates were significantly higher during the first 28 days of culture than after 56 days of culture. This difference is related to the increase in kelp seedling size throughout the experiment, and this increase could affect the requirements and/or optimal environmental conditions for their growth. In addition, comparatively, the rate of total biomass increase for seedlings was significantly higher than the rate of length increase for seedlings, indicating seawater velocity favours greater biomass productivity over length increase. Based on these results, suitable seawater velocities are recommended that would be the most productive for kelp seedling growth on strings in hatchery and nursery phases.
       
  • Riboflavin and lumichrome exuded by the bacterium Azospirillum brasilense
           promote growth and changes in metabolites in Chlorella sorokiniana under
           autotrophic conditions
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Blanca R. Lopez, Oskar A. Palacios, Yoav Bashan, Francisco E. Hernández-Sandoval, Luz E. de-BashanAbstractThe effects of riboflavin and its degradation compound, lumichrome, produced by Azospirillum brasilense on the growth and production of carbohydrates, lipids, and pigments in Chlorella sorokiniana were analyzed. A. brasilense is able to produce and release riboflavin from the first 24 h of incubation in Synthetic Growth Medium (SGM). Synchronic peaks of lumichrome and riboflavin suggest that the former originates from the photodegradation of the latter. The constant growth of bacterial population indicated that riboflavin and lumichrome are cell density-independent. In this study, riboflavin showed a higher effect on the population growth of Chlorella than did lumichrome. The effects of synthetic riboflavin and lumichrome on microalgae were dependent on the concentration of these compounds in the culture media. Lower concentrations of riboflavin (1 ng mL−1 or 10 ng mL−1) enhanced the growth of C. sorokiniana, while the highest amount of riboflavin (100 ng mL−1) showed no effect. Synthetic riboflavin and lumichrome significantly increased the production of carbohydrates compared to the basal medium. Lumichrome showed the highest production of carbohydrates at 48 h while riboflavin at 96 h. Pigments were significantly more affected by the presence of lumichrome than by riboflavin. Enhanced growth and production of carbohydrates and pigments in C. sorokiniana grown in exudates of A. brasilense, suggests a synergistic effect of the riboflavin and lumichrome produced and exuded by this bacterium.
       
  • The use of polyelectrolytes for simultaneous dewatering and fractionation
           of microalgal proteins, lipids, and pigments
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Varun Gejji, Ronald Lacey, Sandun D. FernandoFor making microalgae-based bio-refinery platform sustainable and economically viable, it is necessary to simplify the harvesting process while enabling co-extraction of high-value bio-products from biomass. In this work, the ability of poly-diallyl dimethylammonium chloride (polyDADMAC) to dewater and extract cellular debris, lipids, and pigments to hexane phase while retaining protein fraction in the aqueous phase was investigated. It was observed that different components could be migrated from one phase to the other by modulating the system pH. Close to the isoelectric point, proteins can be retained in the aqueous phase while migrating algal debris to the hexane phase via targeted binding of the polyelectrolyte. Approximately 80% of total proteins were retained in the aqueous phase at pH 4, and ∼90% of cellular debris were migrated to the hexane phase at pH 4.5. Results indicate the possibility of separating multiple components from microalgae in an aqueous-organic solvent two-phase system using polyDADMAC.Graphical abstractGraphical abstract for this article
       
  • Comparing the effects of pre-deposited and pre-mixed powdered activated
           carbons on algal fouling during ultrafiltration
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Yan Zhang, Hongjing Jia, Xinyi Wang, Chengwu Ma, Rongwei Xu, Qiang Fu, Shuang LiAbstractThis investigation compared the effects of pre-deposited and pre-mixed powdered activated carbons (PACs) in submerged ultrafiltration membrane reactors on the distribution of extracellular organic matter (EOM) and its contribution to algal fouling during the filtration of algae-rich water. Experimental results indicate that pre-mixed PAC mitigated algal fouling, whereas pre-deposited PAC exhibited the opposite effect. The porous fouling layer in the pre-mixed case favored the retention of rejected EOM in the concentrated solution owing to a high backward migration rate. Conversely, the dense fouling layer in the pre-deposited case impeded the backward diffusion of EOM, which caused the majority of the rejected EOM to accumulate on the surface and at the bottom of the fouling layer. This difference in EOM distribution led to different cleaning efficiencies. Physical cleaning easily removed both algal cells and pre-mixed PAC from the membrane surfaces, whereas physical and chemical cleanings were both ineffective for pre-deposited PAC, owing to the stronger PAC-EOM attractive force and the NaClO-induced change in the chemical bonds of the PAC and even the membranes. Moreover, decreased algae growth rates were observed in the reactors with PAC as a result of changes in the illumination and the cake layer structure, which could further intensify the contrast between the effects of pre-deposited and pre-mixed PACs on fouling.
       
  • Antioxidative defense response of Ulva prolifera under high or
           low-temperature stimulus
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Juan Juan Yang, Da Chun Yu, Ya Feng Ma, Yi Yin, Song Dong ShenAbstractBecause marine organisms have evolved to adapt to a wide variety of environmental factors on varying temporal and spatial scales, the antioxidative metabolic pathway are different. The aim of this study was to investigate the different antioxidative response of Ulva Prolifera (U. prolifera) that have been exposed to high temperature (UpHT) or low-temperature (UpLT) stresses. The results of our study suggested that mainly UpHT and not UpLT increased the expression of superoxide dismutase (SOD), catalase (CAT), and L-ascorbate peroxidase (APX) more than those in the medium-temperature (UpMT) controls. In addition, biological index analyses indicated that both SOD and CAT activities increased after culturing for 48 h. The chlorophyll levels increased to the highest point after culturing for 4 d in the UpHT group but remained unchanged in the UpLT group. In addition, peroxide (H2O2) and malondialdehyde (MDA) levels increased under UpHT but remained unchanged under UpLT stimuli. We suggest that our findings have significantly improved our understanding of the different molecular mechanisms involved in the tolerance of algae to UpHT or UpLT stimulus, which might explain the seasonal blooms of U. prolifera.
       
  • Photosynthetic conversion of CO2 to hyaluronic acid by engineered strains
           of the cyanobacterium Synechococcus sp. PCC 7002
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Lifang Zhang, Tiago Toscano Selão, Peter J. Nixon, Birgitta NorlingHyaluronic acid (HA), consisting of alternating N-acetylglucosamine and glucuronic acid units, is a natural polymer with diverse cosmetic and medical applications. Currently, HA is produced by overexpressing HA synthases from gram-negative Pasteurella multocida (encoded by pmHAS) or gram-positive Streptococcus equisimilis (encoded by seHasA) in various heterotrophic microbial production platforms. Here we introduced these two different types of HA synthase into the fast-growing cyanobacterium Synechococcus sp. PCC 7002 (Syn7002) to explore the capacity for producing HA in a photosynthetic system. Our results show that both HA synthases enable Syn7002 to produce HA photoautotrophically, but that overexpression of the soluble HA synthase (PmHAS) is less deleterious to cell growth and results in higher production. Genetic disruption of the competing cellulose biosynthetic pathway increased the HA titer by over 5-fold (from 14 mg/L to 80 mg/L) and the relative proportion of HA with molecular mass greater than 2 MDa. Introduction of glmS and glmU, coding for enzymes involved in the biosynthesis of the precursor UDP-N-acetylglucosamine, in combination with partial glycogen depletion, allowed photosynthetic production of 112 mg/L of HA in 5 days, an 8-fold increase in comparison to the initial PmHAS expressing strain. Addition of tuaD and gtaB (coding for genes involved in UDP-glucuronic acid biosynthesis) also improved the HA yield, albeit to a lesser extent. Overall our results have shown that cyanobacteria hold promise for the sustainable production of pharmaceutically important polysaccharides from sunlight and CO2.Graphical abstractGraphical abstract for this article
       
  • Protein extracted from symbiotic culture of Chlorella pyrenoidosa and
           Yarrowia lipolytica shows structure-related detoxifying effects against 2,
           2’-azobis (2-methyl-propanimidamidine) dihydrochloride induced oxidative
           stress
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Qin Wang, Sufen Li, Yuming Zhong, Huifan Liu, Jianliang Liu, Hui Liu, Jian Cheng, Yuqing Huang, Xuanyi Cai, Haijun LiuAbstractWe characterized the co-culture system of Chlorella pyrenoidosa and Yarrowia lipolytica to identify co-culture products of high application value. We first optimized the co-culture parameters using different ratios of algae and Y. lipolytica, which highlighted the competitive relationship between the two organisms. Analysis of pH values indicated that a relatively alkaline symbiotic co-culture might result in undetectable amounts of Y. lipolytica. The ratio of C. pyrenoidosa and yeast did not influence the balance of dissolved oxygen, but showed an influence on the production of chlorophyll A and total protein, with the protein content significantly increasing after 5 days of co-culture. Two protein hydrolysates were extracted from a single culture of C. pyrenoidosa and from a co-culture with Y. lipolytica (3:1 ratio) after 5 days. Structure analysis indicated a high molecular weight and composition of antioxidative-associated amino acids in the co-culture protein, and the two spatial structures were quite diverse; the co-culture protein showed formation of side chain vibrations and unordered structures. Notably, Y. lipolytica could stimulate the formation of superoxide dismutase and the chlorophyll a-b binding protein. In contrast to the protein from C. pyrenoidosa single culture, the co-culture protein showed remarkable protective effects on erythrocytes under oxidative stress, which may be attributed to its specific structure. The activities of antioxidative-associated enzymes were significantly lower than those in the control group (without protein), and the contents of oxidation-related metabolic products, including total glutathione, increased, while the glutathione disulfide content decreased significantly. We hypothesize that this C. pyrenoidosa-specific protein structure obtained from co-culture with Y. lipolytica consists of more exposed hydrophobic residues on the surface of protein molecules, resulting in enhanced antioxidative activity. Therefore, the protein from the yeast-algal symbiotic co-culture has a larger variable structure and shows potent anti-hemolytic activity under oxidative stress.
       
  • Characterisation of organic matter in membrane photobioreactors (MPBRs)
           and its impact on membrane performance
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Yunlong Luo, Rita K. Henderson, Pierre Le-ClechUnderstanding the behaviour of organic materials in bioreactors is an important part of system assessment. This paper focuses on the combined use of liquid chromatography – organic carbon detection and fluorescence excitation–emission matrix spectroscopy for characterising the fate of dissolved organic compounds in membrane photobioreactors operated under different hydraulic and solids retention time. It was found that small amino acids/peptides were largely removed in the reactors, which coincided with the production of biopolymers. The biopolymers were effectively retained (>84%) by the ultrafiltration membrane, in contrast with other algal-derived substances, such as quinones, flavonoids and extracellular chlorophyll a. During long-term low-flux operation (4.5 L/m2 h), preferential deposition of organic matter (e.g. biopolymers) and particles on different fouling layers was observed. The upper fouling layer (obtained by rinsing) was found to contain the greatest amount of organic foulants (211–348 mg/m2) and solids (7.5–15.5 g/m2). By contrast, chemically desorbing layer showed the lowest degree of organic matter build-up, whereby low molecular weight acids were the most abundant organic material. The short-term flux-stepping trials conducted for the same microalgal biomass revealed distinct results, presumably due to the different fouling mechanism involved, where preferential deposition of foulants was not expected given the high driving force.Graphical abstractGraphical abstract for this article
       
  • Assessing the influence of the hydraulic retention time and
           carbon/nitrogen ratio on urban wastewater treatment in a new
           anoxic-aerobic algal-bacterial photobioreactor configuration
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Alma Toledo-Cervantes, Esther Posadas, Isabel Bertol, Sara Turiel, Ana Alcoceba, Raúl MuñozThe influence of the hydraulic retention time (HRT) (2 and 4 days) and the carbon/nitrogen ratio (C/N) (7, 8 and 9) of the wastewater on the treatment of synthetic domestic wastewater was evaluated in a new anoxic-aerobic algal-bacterial photobioreactor configuration operated at solids retention time of 10 d by biomass recycling and withdrawal. The removal of chemical oxygen demand remained between 84% and 89% regardless of the operational conditions. However, the decrease in the HRT from 4 to 2 d entailed reductions in the removal of total nitrogen (TN) and P-PO43− from 87 ± 2% to 62 ± 2% and from 22 ± 5% to 11 ± 1%, respectively. On the other hand, the decrease in the C/N ratio of the wastewater from 9 to 8 and 7 at a HRT of 2 d induced TN removals of 62 ± 4% and 48 ± 4%, respectively. In contrast, P-PO43- removals unexpectedly increased from 11 ± 1% at a C/N ratio of 9 to 53 ± 3% and 47 ± 5% at C/N ratios of 8 and 7, respectively. Finally, biomass settling and recycling supported the enrichment of an algal-bacterial population with good settleability characteristics (suspended solids removals in the settler ∼98%), being Chlorella vulgaris the dominant microalga specie at a C/N ratio of 9 which was gradually replaced by Phormidium sp., as a result of the reduction in the C/N ratio of the wastewater.Graphical abstractGraphical abstract for this article
       
  • Influence of light regime on the performance of an immobilised microalgae
           reactor for wastewater nutrient removal
    • Abstract: Publication date: December 2019Source: Algal Research, Volume 44Author(s): Rachel Whitton, Francesco Ometto, Raffaella Villa, Marc Pidou, Bruce JeffersonAbstractMicroalgae immobilised within a resin shaped into beads have demonstrated the ability to remediate nutrients from wastewater effluents within hydraulic retention times as low as 3 h. Methods to further optimise performance consider parameters relating to the bead with the impact of external conditions seldom investigated. Light is an essential parameter for microalgal growth with its effect on suspended cultures well documented. This work explores the influence of light on nutrient remediation by immobilised microalgae in order to recommend an optimal lighting solution for an immobilised microalgae technology based on Scenedesmus obliquus encapsulated within calcium-alginate beads. White light (400–700 nm) at a photon flux density (PFD) of 200 μmol∙m−2∙s−1 was determined optimal when illuminating a packed bed configuration. When considering phosphate, these conditions supported a remediation rate of 10.7 (± 0.01) mgP∙h−1∙106 beads−1 in comparison to 10.2 (± 0.01) and 10.1 (± 0.01) mgP∙h−1∙106 beads−1 for the blue (465 nm) and red (660 nm) spectra respectively. Although similar performance was demonstrated, light transmission trials determined white light to penetrate to greater bed depths resulting in a larger photoactive zone. A PFD of 200 μmol∙m−2∙s−1 was regarded as optimal when considering performance, attenuation depth and effective use of total supplied light. In addition, photoperiods trials determined lighting periods
       
  • Photoautotrophic production of succinate via the oxidative branch of the
           tricarboxylic acid cycle influences glycogen accumulation in Synechocystis
           sp. PCC 6803
    • Abstract: Publication date: November 2019Source: Algal Research, Volume 43Author(s): Magdalena Mock, Andreas Schmid, Katja BühlerAbstractCyanobacteria are interesting biocatalysts for the sustainable production of value-added compounds, but a functional link of biocatalytic efficiency and cell physiology is missing. Especially the role and structure of the tricarboxylic acid (TCA) cycle in cyanobacteria is not fully understood. Succinate dehydrogenase (SDH) is an essential enzyme linking the TCA cycle to the quinone pool and its substrate succinate is an important platform chemical. We utilized Synechocystis sp. PCC 6803 as a host organism for the photoautotrophic production of succinate via the oxidative branch of the TCA cycle. In Synechocystis sp. PCC 6803 SDH is described to be encoded by three open reading frames (ORF). Four SDH deletion mutants were created and characterized regarding the formation of succinate. Synechocystis_∆sll1625 was the best performing strain accumulating 420 mg L−1 succinate during cultivation in a 1.8 L-photobioreactor under constant illumination. Furthermore, deletion of the SDH resulted in a non-bleaching phenotype and concomitant accumulation of glycogen and succinate during growth at 5% CO2. This substantially influenced cell physiology of the mutant, reflected in decreased cell numbers and higher cell volumes. Thus, the TCA cycle seems to have a key role in controlling carbon fluxes from CO2 into biomass, storage compounds like glycogen, and other carbon sinks.
       
  • Bioremoval of heavy metals from metal mine tailings water using microalgae
           biomass
    • Abstract: Publication date: November 2019Source: Algal Research, Volume 43Author(s): Cynthia Urrutia, Erwin Yañez-Mansilla, David JeisonAbstractThe copper industry generates large quantities of mine tailings water. Thus, this study aims to select a microalgae species that is both tolerant and capable of the bioremoval of heavy metals from metal mine tailings water as well as the potential biorefinery of this microalgae biomass. Chlorella vulgaris and Scenedesmus spinosus were tested for tolerance to metal mine tailings water (MTW) in northern Chile and synthetic treatments of Cu and Mo (0.1 and 0.5 mg/L). Additionally, the biomass generated was characterized to evaluate its potential applications. The main results showed greater tolerance of C. vulgaris cultured in MTW treatment. In fact, high removal efficiency of Cu and Mo was detected for this microalgae in MTW: 64.7% and 99.9%, respectively. Similarly, Cu (55%) and Mo (80.3%) removal was observed at 0.5 mg/L synthetic concentration treatments after 72 h. However, cell wall fluorescence and chlorophyll parameters were mainly affected by 0.5 mg/L Cu synthetic concentration, where the mean fluorescence intensity (MFI) was 878, compared with the other treatments (≥1800). Morphological cell changes in the MTW treatment were observed using SEM images. The presence of Mo on the microalgae surface was detected by 0.47% and 0.82% in both Mo synthetic treatments exposed. Additionally, the characterization of microalgae biomass exposed to MTW showed a higher protein content and a minor difference of lipid content compared with the control treatment, which could be used in biorefinery processes. This study reveals the capability of C. vulgaris to remove heavy metals from this mine tailings water and the effect that occurs in microalgae cells.
       
  • Effect of pulsed electric field treatment on enzymatic hydrolysis of
           proteins of Scenedesmus almeriensis
    • Abstract: Publication date: Available online 14 September 2019Source: Algal ResearchAuthor(s): Sahar Akaberi, Christian Gusbeth, Aude Silve, Divya Senthil Senthilnathan, Elvira Navarro-López, Emilio Molina-Grima, Georg Müller, Wolfgang FreyAmino acids concentrates derived from microalgae biomass through enzymatic protein hydrolysis can improve plant growth by saving the energy that is required for amino acid synthesis from conventional mineral fertilizer resources. To obtain high enzymatic hydrolysis yields, pre-treatment of microalgae biomass prior to enzymatic hydrolysis is suggested for facilitating enzyme access to proteins.Pulsed electric field (PEF) treatment was introduced as a pre-treatment to fresh and concentrated (50 g·kgsus−1 to 80 g·kgsus−1) Scenedesmus almeriensis biomass prior to enzymatic hydrolysis. The concentrated microalgae suspension was treated at an initial conductivity of σ = 1 mS·cm−1 with 1 μs long pulses at an electric field strength of 40 kV·cm−1 and a treatment energy of 75 kJ·kgsus−1 and 150 kJ·kgsus−1. For benchmarking, additional biomass samples were processed by high pressure homogenization (HPH) at 2 kbar and up to 5 passes. Enzymatic hydrolysis was performed by applying the commercial enzymes Alcalase 2.5 L and Flavourzyme 1000 L for 180 min. The amino acids content in supernatant was determined by using the orto-phthaldialdehyde (OPA) assay.PEF treatment at both energy inputs and HPH treatment at 2 kbar, 5 passes, revealed the same hydrolysis kinetics and the same final value of the degree of hydrolysis (DH) of 50% ± 2%. The energy demand for PEF pre-treatment amounts to 0.75 MJ·kgdw−1 when processing biomass at 100 gdw·l−1. After both pretreatments, incomplete protein hydrolysis could be detected by SDS-PAGE analysis of residual biomass. Most feasible, hydrophobic protein fractions and protein aggregation impede complete protein hydrolysis by the applied enzyme cocktail.Since PEF treatment preserves cell shape and biomass separability and thus enables cascade processing, it is suggested as alternative downstream processing method for the production of amino acids concentrates from microalgae biomass.Graphical abstractUnlabelled Image
       
  • Corrigendum to “Application of aqueous alkaline extraction to remove ash
           from algae harvested from an algal turf scrubber” [Algal Res. 35 (2018)
           370–377]
    • Abstract: Publication date: Available online 13 September 2019Source: Algal ResearchAuthor(s): John E. Aston, Bradley D. Wahlen, Ryan W. Davis, Anthony J. Siccardi, Lynn M. Wendt
       
  • Combination of Light Emitting Diodes (LEDs) for photostimulation of
           carotenoids and chlorophylls synthesis in Tetradesmus sp.
    • Abstract: Publication date: November 2019Source: Algal Research, Volume 43Author(s): Vanessa Daneluz Gonçalves, Márcia Regina Fagundes-Klen, Daniela Estelita Goes Trigueros, Adilson Ricken Schuelter, Alexander Dimitrov Kroumov, Aparecido Nivaldo MódenesIn this work, Tetradesmus sp. was investigated regarding biomass and pigment production. The cultivation of Tetradesmus sp. was carried out in a BG-11 medium in addition to a vertical tubular photobioreactor (PBR) irradiated with different spectral combinations and intensities, within a 24:00 h photoperiod. The LEDs emitting light with white; red; yellow; green and blue spectrum were used alone and/or combined, with intensities varying from 13 to 190 μmol m−2 s−1. ANOVA suggested significant effects of the light combination, intensity and interaction between the factors on biomass, carotenoid and chlorophyll responses. The blue light accelerated the growth of Tetradesmus sp. in all three experiments. The combinations white:green (95 μmol m−2 s−1), red:blue (50 μmol m−2 s−1) and blue (25 μmol m−2 s−1) favored biomass growth; while white:green (190 μmol m−2 s−1), red:green (50 μmol m−2 s−1) and red (25 μmol m−2 s−1) favored the synthesis of carotenoids and chlorophylls. Culture reproduction under the spectral regions favoring pigment synthesis indicated that Tetradesmus sp. was photostimulated to synthesize both pigments, especially with red:green (50,50%) at 50 μmol m−2 s−1, where the highest production of carotenoids (6.09 ± 0.29 mg (g biomass)−1) and chlorophyll a (10.08 ± 0.75 mg (g biomass)−1) was obtained.Graphical abstractUnlabelled Image
       
  • Productivity of Nannochloropsis oceanica in an industrial closely spaced
           flat panel photobioreactor
    • Abstract: Publication date: November 2019Source: Algal Research, Volume 43Author(s): N.H. Norsker, M. Michiels, P.M. Slegers, G.L.A.M. Swinkels, M.J. Barbosa, R.H. Wijffels
       
  • Demonstration of the potential of Picochlorum soloecismus as a microalgal
           platform for the production of renewable fuels
    • Abstract: Publication date: November 2019Source: Algal Research, Volume 43Author(s): C. Raul Gonzalez-Esquer, Kimberly T. Wright, Nilusha Sudasinghe, Carol K. Carr, Claire K. Sanders, Aiko Turmo, Cheryl A. Kerfeld, Scott Twary, Taraka DaleAbstractPhotosynthetic microbes are considered promising biofactories for transforming inorganic carbon from the atmosphere into a renewable source of chemicals and precursors of industrial interest; however, there continues to be a need for strains that demonstrate high productivity, environmental robustness, and the potential to be genetically manipulated. Genome sequencing and biochemical characterization of promising culture collection microalgae strains, as well as the isolation of previously unidentified strains from the environment or mixed cultures, bring us closer to the goal of decreasing the cost-per-gallon of algal biofuels by identifying new and promising potential production strains. The halotolerant alga Picochlorum soloecismus was isolated from the culture collection strain, Nannochloropsis salina CCMP 1776. Here, we show that P. soloecismus accumulates moderate levels of fatty acids and high levels of total carbohydrates and that it can effectively grow in a range of salinities. In addition, we make use of its sequenced genome to compare it to other biofuel production platforms and to validate the capacity for engineering this strain's genome. Our work shows that Picochlorum soloecismus is a candidate production strain for the generation of renewable bioproducts.
       
  • Prospects of using biomass of N2-fixing cyanobacteria as an organic
           fertilizer and soil conditioner
    • Abstract: Publication date: November 2019Source: Algal Research, Volume 43Author(s): Mauro Do Nascimento, Marina E. Battaglia, Lara Sanchez Rizza, Rafael Ambrosio, Andres Arruebarrena Di Palma, Leonardo CurattiIncreasing production of N-fertilizers is mandatory to support the expected demand of food over the next decades. While reduced access to N-fertilizers compromises food security in some regions of the world, incorrect management in other regions causes detrimental effects on the environment. Biological N2-fixation is a natural process for N-fertilization of plants in natural environments which could only be partially exploited in intensive agriculture. This is mainly because the current technology of crop inoculation with live microorganisms is often constrained by the inoculant's survival and propagation in the agricultural environment.In this study, we pursued a controlled eutrophication approach to recycling nutrients from agro-industrial runoffs for the production of an organic fertilizer and soil conditioner. Biomass of a N2-fixing cyanobacterium was obtained using a P-enriched fermentation vinasse as a sole source of macronutrients. The cyanobacterial biomass substituted for urea in wheat growth in artificial semi-arid soil, especially when sporadic watered simulating a semi-arid rainfall regime. Comparative analyses suggested a higher persistence of the organic fertilizer in the soil than an equivalent amount of urea.This study advocates the convenience of concentrating nutrients from industrial wastewater into biomass of N2-fixing cyanobacteria for their re-use in crop fertilization. It discusses the advantages of separating biological fertilizer production from crop cultivation in order to circumvent the odds of the microorganisms' acclimation to the agronomic conditions, and the techno-economic challenges towards maturation of the proposed technology.Graphical abstractUnlabelled Image
       
  • Phosphorus starvation and luxury uptake in green microalgae revisited
    • Abstract: Publication date: November 2019Source: Algal Research, Volume 43Author(s): Alexei Solovchenko, Inna Khozin-Goldberg, Irina Selyakh, Larisa Semenova, Tatiana Ismagulova, Alexandr Lukyanov, Ilgar Mamedov, Elizaveta Vinogradova, Olga Karpova, Ivan Konyukhov, Svetlana Vasilieva, Peter Mojzes, Cor Dijkema, Margarita Vecherskaya, Ivan Zvyagin, Ladislav Nedbal, Olga GorelovaAbstractPhosphorus (P) is central to storing and transferring energy and information in living cells, including those of microalgae. Many microalgal species dwelling in low P environments are naturally equipped to take up and store P whenever it becomes available through a complex phenomenon known as “luxury P uptake.” Its research is required for better understanding of the nutrient geochemical cycles in aquatic environments but also for biotechnological applications such as sequestration of nutrients from wastewater and production of algal fertilizers. Here, we report on our recent insights into luxury P uptake and polyphosphate formation originating from physiological, ultrastructural, and transcriptomic evidence. The cultures pre-starved of P and re-fed with inorganic phosphate (Pi) exhibited a bi-phasic kinetics of Pi uptake comprising fast (1–2 h after re-feeding) and slow (1–3 d after re-feeding) phases. The rate of Pi uptake in the fast phase was ca. 10 times higher than in the slow phase with an opposite trend shown for the cell division rate. The transient peak of polyphosphate accumulation was determined 2–4 h after re-feeding and coincided with the period of slow cell division and fast Pi uptake. In this phase, the microalgal cells reached the highest P content (up to 5% of dry cell weight). The P re-feeding also reversed the characteristic changes in cell lipids induced by P starvation, namely increase in the major membrane glycolipid (DGDG/MGDG) ratio and betaine lipids. These changes were reversed upon Pi re-feeding of the starved culture. Electron microscopy revealed the ordered organization of vacuolar polyphosphate indicative of the possible involvement of an enzyme (complex) in their synthesis. A candidate gene encoding a protein similar to the vacuolar transport chaperone (VTC) protein, featuring an expression pattern corresponding to polyphosphate accumulation, was revealed. Implications of the findings for efficient biocapture of phosphorus are discussed.
       
  • Hydrothermal liquefaction of residual microalgae biomass after pulsed
           electric field-assisted valuables extraction
    • Abstract: Publication date: November 2019Source: Algal Research, Volume 43Author(s): Bingfeng Guo, Boda Yang, Aude Silve, Sahar Akaberi, Daniel Scherer, Ioannis Papachristou, Wolfgang Frey, Ursel Hornung, Nicolaus DahmenEfficient extraction of valuable products from microalgae and utilization of the residual biomass for biofuel production appear to bring economic benefits for the microalgae biorefineries. The pulsed electric field (PEF) method has been proposed as a promising pre-treatment for microalgae wet extraction. For conversion of microalgae biomass and residues, hydrothermal liquefaction (HTL) is considered a suitable method. Here, a combination of PEF-assisted valuables extraction of microalgae and HTL of the residual biomass is studied for the first time. The microalgae Auxenochlorella protothecoides, Chlorella vulgaris, and Scenedesmus almeriensis were cultivated, harvested, treated by PEF, and then subjected to lipid extraction, protein extraction, or extraction of amino acids after enzymatic protein hydrolysis. The residual biomass obtained from PEF-assisted valuables extraction was subjected to HTL in micro autoclaves at a temperature of 350 °C and pressure of 25 MPa for 15 min holding time. Product yields and analytical results obtained by elemental content measurement, 1H-nuclear magnetic resonance spectroscopy, Fourier-transform infrared spectroscopy, and gel permeation chromatography show that PEF alone has no significant direct influence on microalgae HTL. The harsh HTL conditions decisively determine the product yields and biocrude quality. However, PEF enhances the lipid extraction yield from 4 wt% to 33 wt%. Consequently, the biocrude yield decreases from 58 wt% to 43.2 wt%. Moreover, PEF boosts the protein extraction yield from almost zero to 41.6 wt% of the total protein, resulting in an increased biocrude yield by about 2 wt%. Finally, PEF accelerates the formation of amino acids by enzymatic hydrolysis, improving the extraction efficiency up to 150% in the first 60 min of the extraction. The extracted residue promises to produce a biocrude yield higher by 6 wt% and a better biocrude quality with lower nitrogen content. An overall mass balance of PEF-assisted valuables extraction and HTL is presented.Graphical abstractUnlabelled Image
       
  • The genus Prototheca (Trebouxiophyceae, Chlorophyta) revisited:
           Implications from molecular taxonomic studies
    • Abstract: Publication date: November 2019Source: Algal Research, Volume 43Author(s): Tomasz Jagielski, Zofia Bakuła, Jan Gawor, Kacper Maciszewski, Wolf-Henning Kusber, Mariusz Dyląg, Julita Nowakowska, Robert Gromadka, Anna KarnkowskaThe only algae which are able to inflict disease on humans and other mammals through active invasion and spread within the host tissues belong to either of two genera: Chlorella and Prototheca. Whereas Chlorella infections are extremely rare, with only two human cases reported in the literature, protothecosis is an emerging disease of humans and domestic animals, especially dairy cows. The genus Prototheca, erected by Krüger in 1894, has undergone several significant revisions, as more phenotypic, chemotaxonomic, and molecular data have become available. Due to this, a large number of Prototheca strains have been accumulated in public culture collections, over the years, where they still exist under outdated or invalid infraspecific or species names. In this study, the partial cytb gene was used as a marker to revise the taxonomy and nomenclature of a set of Prototheca strains, preserved in major algae culture repositories worldwide.Within the genus, two main lineages were observed, with a dominance of typically dairy cattle-associated (i.e. P. ciferrii, formerly P. zopfii gen. 1, the here validated P. blaschkeae, and one newly erected species, namely P. bovis, formerly P. zopfii gen. 2) and human-associated (i.e. P. wickerhamii, P. cutis, P. miyajii) species, respectively. In the former lineage, three newly described species were allocated, namely P. cookei sp. nov., P. cerasi sp. nov., and P. pringsheimii sp. nov., and the lecto- and epitypified P. zopfii species. The second, or so-called P. wickerhamii lineage, incorporated a newly proposed species of P. xanthoriae sp. nov. These protothecans were shown as the closest relatives of the photosynthetic genera, Chlorella and Auxenochlorella. The environmental species P. ulmea was synonymized with the lecto- and epitypified P. moriformis species.For circumscription and differentiation of Prototheca spp., the use of phenotypic characters, and morphology in particular, is of limited value and should rather be auxiliary to molecular marker-based approaches. As demonstrated in our previous study and corroborated in the present one, the cytb gene provides higher resolution than the conventional rDNA markers, and currently represents the most efficient barcode for the Prototheca algae.Graphical abstractUnlabelled Image
       
  • Functional and phenotypic flow cytometry characterization of
           Picochlorum soloecismus
    • Abstract: Publication date: November 2019Source: Algal Research, Volume 43Author(s): Christina R. Steadman Tyler, Claire K. Sanders, Reece S. Erickson, Taraka Dale, Scott N. Twary, Babetta L. MarroneMultiple physiological traits essential for efficient cellular function are important when considering the selection and engineering of algal species for biofuel and bioproduct generation. Bioengineering methods have become more ubiquitous producing several novel algal lines with potentially enhanced traits. Complex metabolic interactions, however, require greater depth in characterizing cellular responses to delineate mechanistic understanding. We have developed fluorescence-based high-throughput flow cytometry protocols to facilitate characterization of cell morphology, membrane permeability, metabolic activity, cell viability, intracellular pH, and reactive oxygen species in isolates derived from the species Picochlorum soloecismus. Flow cytometry parameters were optimized for each assay. This suite of molecular flow cytometry probes and procedures can be utilized for rapid screening of optimal phenotypes in microalgae under various environmental conditions as new technical strategies for improving algae strain productivity are established.Graphical abstractUnlabelled Image
       
  • Simultaneous dissolution and uptake of nutrients in microalgal treatment
           of the secondarily treated digestate
    • Abstract: Publication date: November 2019Source: Algal Research, Volume 43Author(s): Nilüfer Ülgüdür, Tuba H. Ergüder, Göksel N. DemirerAnaerobic digestion processes result in large volumes of digestates which still require the development of elaborate and viable management options to improve the sustainability of these processes. Coupling of secondary anaerobic treatment with a microalgal nutrient removal process may serve benefits such as residual biogas and associated greenhouse gas capture from the digestate content, microalgal biomass build-up and its further valorization. This study investigated the applicability a microalgal nutrient removal process in a secondarily treated digestate (the digestate of a digestate) as a complementary unit. The results indicated that up to 100% dissolved reactive phosphorus (DRP), 97.8% total dissolved phosphorus (TDP) and 93.7% ammonium nitrogen (NH4+-N) removal could be attained in the treatment of the digestate of a digestate using microalgal cultures. Folding phosphorus concentrations via dissolution was found to compensate for dilution related phosphorus deficiency for microalgal growth. Microalgal biomass obtained by the end of operation could be concentrated from 6.4‐15.5 mg/L to 164.2–502.6 mg/L (2100–7900%) by simple gravity settling which was correlated with the prevalence of agglomerated particles in the size range of 10–100 μm. The results demonstrated not only the applicability of the microalgal process after secondary anaerobic treatment of the digestate, but also brought about the dissolution concept for nutrients during microalgal growth.Graphical abstractUnlabelled Image
       
  • Effects of gluconate on biomass improvement and light stress tolerance of
           Haematococcus pluvialis in mixotrophic culture
    • Abstract: Publication date: November 2019Source: Algal Research, Volume 43Author(s): Na Pang, Xiangyu Gu, Xiao Fu, Shulin ChenAbstractMixotrophic culture shows great potential for improving microalgal growth. Currently, the complex roles of organic carbon for biomass enhancement in mixotrophic culture remain a topic of investigation. In this study, the green microalgae Haematococcus pluvialis was cultured for biomass production under mixotrophic conditions using a new organic carbon source, sodium gluconate. Experiments feeding H. pluvialis with sodium gluconate, sodium acetate, and ribose were conducted. The best growth performance was achieved with sodium gluconate exposed to high light intensity. With the addition of 2 g/L gluconate, the maximum cell number achieved 2.43 × 106/mL at 105 ± 3 μmol m−2 s−1 light intensity, a five-fold increase over that of heterotrophic culture and 89.8% increase over ribose-fed mixotrophic culture. The maximum dry cell weight was 2.09 g/L with a specific growth rate of 0.48 d−1, an increase of 77.1% over that with optimal ribose conditions. The cellular motility of microalgae was affected by the culture age and light intensity. At lower light intensity (45 ± 3 μmol m−2 s−1), the highest motile cell number was 7.33 × 105/mL with gluconate. Under mixotrophic conditions, the culture with gluconate kept high numbers of motile cells with the increase of light intensity, 3.17 × 105/mL at 105 ± 3 μmol m−2 s−1. Even high light intensity caused decrease in cellular motility, gluconate-fed microalgae still had active cell activity with more motile cells compared with that fed with ribose. Microalgae with gluconate triggered resistant response against high light intensity under mixotrophic conditions. Moreover, H. pluvialis showed great potential in effective photosynthesis with higher chlorophyll content under high light condition. These results indicate that gluconate is an effective organic carbon source for improving biomass productivity, cell activity, and photosynthesis efficiency for H. pluvialis in mixotrophic culture.
       
  • Investigating the modulation of metabolites under high light in
           mixotrophic alga Asteracys sp. using a metabolomic approach
    • Abstract: Publication date: November 2019Source: Algal Research, Volume 43Author(s): Akanksha Agarwal, Kashif M. Shaikh, Krushna Gharat, Pannaga P. Jutur, Reena A. Pandit, Arvind M. LaliAbstractMetabolomic fluctuations in microalgal cells under mixotrophic growth regimes are scarcely understood. Our study explores these changes in an oleaginous microalga, Asteracys sp. when grown mixotrophically under high irradiances. Biomass production under autotrophic and mixotrophic regimes were studied at two light intensities (LL; 100 μmol photons m−2 s−1 and HL; 900 μmol photons m−2 s−1) for Asteracys sp. Studies on supplementation of external carbon such as glucose (mixotrophic mode) under different light intensities has not been demonstrated in context with enhanced biomass production. In the present study, we have provided external source of carbon as glucose in LL and HL regimes and observed a marked influence of glucose assimilation on the overall machinery of the cell. Our qualitative metabolomics reveals a stress-like phenomenon in Asteracys sp. under HL with enhanced biomass. In overview, our data analysis highlights few metabolites such as trehalose, proline and α-tocopherol that showed significant changes in response to light as well as in growth regime. Our analysis predicts an interrelation cross talk between maltose and sucrose pathways within cells owing to possible alteration in starch degradation under the influence of light. However, mixotrophy with additional carbon supplementation in presence of light did not alter or enhance lipid biosynthesis. In conclusion, our hypothesis indicates modulation of metabolites in presence of glucose under high light would rather facilitate rearrangement in metabolic pathways for enhanced biomass production.
       
  • Chlorella vulgaris bioaccumulates excess manganese up to 55× under
           photomixotrophic conditions
    • Abstract: Publication date: November 2019Source: Algal Research, Volume 43Author(s): Amanda L. Smythers, Nicole L. Perry, Derrick R.J. KollingAbstractManganese is a transition metal that can accumulate in waterways in concentrations above natural abundance due to the mining, metallurgy, and agricultural industries. While chemical technologies for manganese removal are abundantly available, the high solubility of manganese in aqueous solutions causes steep decreases in removal efficiency and generates hazard waste that can be problematic to store. Chlorella vulgaris, a robust, unicellular green alga, offers an environmentally friendly alternative to chemical methods with the added economic potential of generating value-added products. In this study, C. vulgaris was exposed to increasing concentrations of manganese and monitored for bioaccumulation and adsorption. Additionally, cells were monitored for biochemical changes by assaying for terminal biochemical composition and determining photosynthetic activity throughout the life cycle of the culture. Evidence suggests that C. vulgaris can bioaccumulate manganese to an intracellular concentration of 733.3 mM and remove up to 56.74% of the manganese from highly concentrated media through both intracellular bioaccumulation and membrane-bound adsorption. Interestingly, the cultures exposed to high concentrations were able to accumulate manganese up to 55× the external concentration without experiencing inhibitory effects resulting from metal toxicity. Furthermore, cultures exposed to increased manganese displayed higher amounts of protein biosynthesis and an increase in photosynthetic capacities, potentially related to structural changes in the light harvesting antenna complexes of photosystem II.
       
  • Predicting removal kinetics of biochemical oxygen demand (BOD) and
           nutrients in a pilot scale fed-batch algal wastewater treatment system
    • Abstract: Publication date: November 2019Source: Algal Research, Volume 43Author(s): Isuru S.A. Abeysiriwardana-Arachchige, Nagamany NirmalakhandanOur previous reports have presented single-step treatment of primary-settled urban wastewater by a mixotrophic alga, Galdieria sulphuraria. Here, we present an approach to predict the operational cycle time, t*, required to meet the discharge standards for ammoniacal-nitrogen (NH3-N), phosphate (PO4) and biochemical oxygen demand (BOD) in fed-batch mode, under varying influent concentrations. First order removal rates of NH3-N, PO4 and BOD, determined using data from 10 fed-batch cycles in a pilot scale system (700 L), were used to predict their temporal fate and t* in 30 other cycles. Predicted concentrations of NH3-N, PO4, and BOD and t* over a wide range of influent concentrations agreed well with the measured ones, with root mean square errors, respectively, of 2.06 mg/L, 0.23 mg/L, 2.88 mg/L and 0.30 days. The coefficient of determination between the measured and the predicted values were as follows: for NH3-N: r2 = 0.82, n = 90; for PO4: r2 = 0.87, n = 90; for BOD: r2 = 0.70, n = 30; and for t*: r2 = 0.61, n = 30. The validity of the model in predicting temporal concentration profiles of NH3-N, PO4 and BOD reflected by Janus quotient (respectively of 0.85, 0.87 and 0.61) is comparable to or better than those reported in the literature. Sensitivity analysis procedures identified the influent concentration of PO4 as the most sensitive parameter in predicting t*.Graphical abstractUnlabelled Image
       
  • Mono- and poly-unsaturated triacylglycerol fractionation from Chlorella
           sp. using supercritical carbon dioxide
    • Abstract: Publication date: November 2019Source: Algal Research, Volume 43Author(s): Thomas Alan Kwan, Julie Beth ZimmermanExtraction of unsaturated triacylglycerols from microalgae is important towards the viability of a sustainable biorefinery. Supercritical carbon dioxide was used to extract and enrich the mono- and poly-unsaturated triacylglycerols using a step-wise extraction scheme where the supercritical carbon dioxide density was increased from 450 to 550 to 750 mg/ml over a total of 170 min. At the lowest density of 450 mg/ml, saturated fatty acid triacylglycerols comprised 88% (mol) of the extract while mono- and poly-unsaturated triacylglycerols were over 60% and 80% (mol) at 550 and 750 mg/ml supercritical carbon dioxide respectively. This extraction scheme was informed by solubility and intermolecular interactions of mixed triacylglycerols. Chrastil's solubility parameters suggested that saturated fatty acid triacylglycerols were susceptible to intermolecular interactions while mono- and poly-unsaturated triacylglycerols are less susceptible to these interactions. Combined with the low solubility of mono- and poly-unsaturated triacylglycerols and high solubility of saturated fatty acid triacylglycerols at low densities, these phenomena were combined to demonstrate how supercritical carbon dioxide can be tuned to fractionate mono- and poly-unsaturated triacylglycerols from saturated fatty acids from microalgae. This is significant as supercritical carbon dioxide extraction technology is scalable and suitable as a first unit process for separations in a biorefinery setting.Graphical abstractUnlabelled Image
       
  • Homogenization significantly enhances growth of macroalga Saccharina
           japonica female gametophytes
    • Abstract: Publication date: November 2019Source: Algal Research, Volume 43Author(s): Yun Zhang, Yingdi Zhang, Mengying Li, Li Li, Xianming Tang, Jiangtao GaoAbstractIn this work, a novel photobioreactor with blade impellers was designed and developed to enhance filamentous cell cultures derived from gametophytes of the brown macroalga Saccharina japonica. Such design efficiently homogenized and dispersed the culture filaments in the photobioreactor, which favored the vegetable growth by providing even exposure of almost all of female gametophytes to sufficient light and nutrients in the culture. As compared to conventional photobioreactors, the biomass productivity and specific growth rate increased by 141% and 51%, respectively, which resulted from the enhanced photosynthetic efficiency.The photobioreactor developed in this work enables an efficient light-to-biomass conversion, demonstrates a hitherto undescribed significant enhancement in photosynthesis activity and algal biomass and provides a viable and promising window for large-scale indoor applications.
       
  • Benchtop flow NMR spectroscopy as an online device for the in vivo
           monitoring of lipid accumulation in microalgae
    • Abstract: Publication date: November 2019Source: Algal Research, Volume 43Author(s): Dylan Bouillaud, Vladimir Heredia, Thomas Castaing-Cordier, Delphine Drouin, Benoît Charrier, Olivier Gonçalves, Jonathan Farjon, Patrick GiraudeauThe sustainable production of lipids by microalgae is widely developed among the bioprocess community targeting various applications such as feed, food, health or bioenergy. The cultivation of microalgae needs dedicated systems with the optimal illumination geometry. Performing non-invasive online analyses on these bioprocesses is limited to few analytical techniques, often based on optical properties and can however rarely be related to intracellular products. The real-time knowledge of the lipids accumulation in microalgae is –in this case– not possible. In this article, the proof-of-concept that the recent benchtop NMR spectroscopy device can be used for the non-invasive and selective detection of lipids inside microalgae cells is carried out. Three cultures of Nannochloropsis gaditana were analyzed in flow conditions. The relative quantitative feature is confirmed by the correlation with a reference technique classically used for lipid analysis, i.e. the FAME (Fatty Acid Methyl Ester) profiling by gas chromatography.Graphical abstractUnlabelled Image
       
  • Identification and theoretical explanation of chemical composition against
           α-amylase in the n-hexane extract from Sargassum fusiforme
    • Abstract: Publication date: November 2019Source: Algal Research, Volume 43Author(s): Jiao Yang, Chang Liu, Hengjiang Cai, Dongyu Gu, Zhenni Ji, Xinfeng Guo, Jing Tian, Jing Meng, Yi YangSargassum fusiforme is an edible alga that possesses a number of bioactivities, such as antidiabetic effects. In the present study, the n-hexane extract of S. fusiforme showed inhibitory activity against α-amylase. To interpret the α-amylase inhibitory activity of this extract, a method based on GC–MS and molecular docking was established. A total of 25 compounds were identified using GC–MS and then individually docked with α-amylase to simulate interactions between the latter and the ligands. Among the compounds determined, phenol, 2,2′-methylenebis[6-(1,1-dimethylethyl)-4-methyl- (PMDM) was completely enfolded in the active site of α-amylase via hydrophilic and electrostatic interactions, van der Waals forces, hydrogen bonds and π-π stacking interactions and showed the lowest binding energy (−6.25 kcal/mol). The activity of PMDM against α-amylase was further tested and verified in vitro, and its IC50 was found to be 79.96 ± 0.34 μM. Thus, this compound is responsible for the α-amylase inhibitory activity of the n-hexane extract of S. fusiforme.Graphical abstractUnlabelled Image
       
  • An effective approach of bacterial siderophore as nitrogen source
           triggering the desired biochemical changes in microalgae Chlorella
           variabilis ATCC 12198
    • Abstract: Publication date: November 2019Source: Algal Research, Volume 43Author(s): Soundarya Rajapitamahuni, Khushbu Bhayani, Pooja Bachani, Vamsi Bharadwaj S.V, Sandhya MishraThe present study was aimed to check whether catecholate siderophore can serve as a nitrogen source besides iron for microalgae. Catecholate siderophore from Idiomarina loihiensis RS 14 contains 13% nitrogen which can be a potential nitrogen source. Bacterial supernatant containing siderophores with different inoculum ratio was used to check the growth of Chlorella variabilis ATCC 12198. Nitrogen starvation with two stage cultivation was employed here to trigger the accumulation of lipid and carbohydrate. In continuous cultivation, the highest productivity of DCW was observed in 1%, 760 mg/L compared to culture grown at 0.5%, with an increase of 42.2% higher biomass productivity (21.66 mg/L/day). Similarly, in 1%, C. variabilis produced total 30% of lipid content which contains 75% of neutral lipid. Highest carbohydrate was (49.29%) found in cells grown under 9 days of stress in 1% followed by cells grown under 3 days of stress in 5% (46.52%) in stage II cultivation.Graphical abstractUnlabelled Image
       
  • Compatible solutes profiling and carbohydrate feedstock from diversified
           cyanobacteria
    • Abstract: Publication date: November 2019Source: Algal Research, Volume 43Author(s): Nitin Keshari, Muriel Gugger, Tao Zhu, Xuefeng LuAbstractCyanobacteria are promising cell factories for producing high-value bioproducts. They accumulate low molecular mass organic molecules under salinity stress conditions, which are known as compatible solutes, e.g. sucrose, trehalose, and glucosylglycerol (GG). The physiological properties of compatible solutes sort them as the potential bioproducts for applications in the field of health, pharmacy, and cosmetic sectors. During last few decades, mostly model cyanobacterial strains (unicellular from freshwater and marine habitats) have been targeted for the biochemical and molecular characterization of compatible solutes accumulation, while, the study on other cyanobacteria from extreme/stressful habitats are scanty. The advantage for selecting multicellular cyanobacteria in the present study is their easier harvesting mode over unicellular strains which are one of the primary concerns for the cost-effective production of desired products at pilot scale. Therefore, five cyanobacterial strains with diverse morphotypes belonging to subsection I (Unicellular), II (Baeocytous), III (Filamentous), and V (Ramified) isolated from extreme/stressful habitats (sewage pond and hot spring including freshwater strain as a reference) were screened for salt tolerance, compatible solutes profiling, and sugar feedstock production. High GG, sucrose, and glycogen production were found in Leptolyngbya sp. PCC 8913, Chroogloeocystis siderophila NIES-1031 and Fischerella major NIES-592, respectively. Under salt stress, Leptolyngbya sp. PCC 8913 showed a GG production of 101 ± 12 mg/L/OD730, which is significantly higher than that of the model strain Synechocystis sp. PCC 6803. Fischerella major NIES-592 and Oscillatoria laetevirens NIES-31 were identified as novel trehalose-producing cyanobacteria. The key genes involved in production of compatible solutes among these cyanobacteria were also studied. Thus, the results not only displayed the potential cyanobacteria for production of GG, sucrose, trehalose and glycogen but also address the metabolic pathways for the compatible solutes biosynthesis in diversified cyanobacteria, which can be further targeted for the in-depth study to enhance the production using molecular approaches.
       
  • Towards phosphorus recycling for agriculture by algae: Soil incubation and
           rhizotron studies using 33P-labeled microalgal biomass
    • Abstract: Publication date: November 2019Source: Algal Research, Volume 43Author(s): Nina Siebers, Diana Hofmann, Henning Schiedung, Alexander Landsrath, Bärbel Ackermann, Lu Gao, Peter Mojzeš, Nicolai D. Jablonowski, Ladislav Nedbal, Wulf AmelungAbstractAlgae effectively accumulate phosphorus (P) from the environment, qualifying them as a promising novel P fertilizer. We hypothesized that P in algae can be rapidly transformed in soil and mobilized for plant growth. To determine the fate of algal fertilizer in soil and to trace its efficiency for plant uptake, we labeled the algae Chlorella vulgaris with the radioisotope 33P. To optimize the labeling we studied P-uptake dynamics in detail using a pre-starved culture and additionally monitored polyphosphate (Poly-P) and organic carbon (C) reserve pools by Raman microscopy. Using an optimized labeling procedure, the concentrations and distribution of both algae-derived 33P and mineral fertilizer 33P (control) were characterized in incubation and rhizotron experiments. Soil incubation was performed with four major reference groups (Andosol, Alisol, Cambisol, and Vertisol). To assess 33P plant uptake we grew wheat in rhizotrons on Cambisol. Soil analyses at different incubation times demonstrated sequential 33P fractionation, while plant uptake of algae-derived 33P was followed using sequential autoradiographic imaging. We found that the algae increased labile P pools comprising Resin- and NaHCO3-extractable P in soils during the first 2 weeks of incubation, similar to the effects of NPK fertilizer. The soils with elevated concentrations of Fe- and Al-oxides (Andosol and Alisol) immediately bound 55 to 80% of the applied fertilizer 33P into the moderately available NaOH-P fraction, whereas the soils with lower concentrations of Fe/Al-oxides (Cambisol, Vertisol) stored 35–71% of the algal-P in the labile fraction. The rhizotron experiments visually supported the release and plant-uptake of algal 33P, thus verifying the suitability of algal-fertilizer for plant growth.
       
  • Comparative proteomics investigation of central carbon metabolism in
           Euglena gracilis grown under predominantly phototrophic, mixotrophic and
           heterotrophic cultivations
    • Abstract: Publication date: November 2019Source: Algal Research, Volume 43Author(s): Mafruha T. Hasan, Angela Sun, Bishal Khatiwada, Leon McQuade, Mehdi Mirzaei, Junior Te'o, Graham Hobba, Anwar Sunna, Helena NevalainenAbstractEuglena gracilis can use a wide range of organic carbon sources, as well as CO2 from the atmosphere. This metabolic versatility is owed to the genome of E. gracilis that can encode a wide range of enzymes. Many of these enzymes are regulated post-transcriptionally, allowing the cells to adapt quickly to changes in their surroundings. Here we investigated the effect of predominantly phototrophic (PT), mixotrophic (MT) and heterotrophic (HT) cultivation on central carbon metabolism in E. gracilis Z using label-free shotgun proteomics. Differential expression between isozymes was observed based on the cultivation condition. A hexokinase enzyme identified in the published transcriptome was not detected in the proteome. Instead, a high-specificity glucokinase appeared to conduct the first step of glycolysis. Two candidates for paramylon synthase were identified (EgGSL1 and EgGSL2), of which the predominant EgGSL2 protein was detected across all growth conditions, while EgGSL1 was only detected in the presence of light (PT and MT cultivations). Proteomic analysis revealed that the oxidative pentose phosphate pathway also plays a key role in glucose metabolism under MT and HT cultivation. Some chloroplast-encoded proteins and enzymes of the Calvin pathway were detected under HT cultivation indicating regulation at the post-translational level. The carbon metabolic pathways investigated here in terms of proteomic changes provide new information, as well as validate data presented elsewhere with quantitative proteomics, adding to the existing knowledge of metabolism in E. gracilis. Putative functional annotations of several proteins that were previously unidentified are also provided.
       
  • Determination of individual chain length and chain-length distribution of
           polyphosphates in microalgae by 31P-DOSY-NMR
    • Abstract: Publication date: November 2019Source: Algal Research, Volume 43Author(s): Liming Wang, Christina Kuchendorf, Sabine WillboldAbstractDue to its ecological and biotechnological relevance, polyphosphate in microalgae is currently the focus of intense research. Numerous biological functions are performed by or dependent on polyphosphate, and they depend, among other factors, on its chain length. Chain length determination is important for understanding polyphosphate metabolism and for maximizing intracellular polyphosphate abundance per unit weight of biomass. 31P-DOSY NMR virtually separates various polyphosphate polymers in a mixture based on different translational diffusion coefficients. The diffusion coefficient of a polyphosphate molecule correlates with its molecular weight, enabling determination of individual chain lengths. Moreover, the polydispersity index can also be uniquely determined by DOSY as a measure of the overall chain-length distribution of polyphosphates. By contrast, conventional 31P NMR is only able to estimate the average chain length of the entire polyphosphate pool. Therefore, DOSY provides the opportunity to deepen our insight into polyphosphate metabolism and dynamics in algal biomass.
       
  • The past, present and future of algal continuous cultures in basic
           research and commercial applications
    • Abstract: Publication date: November 2019Source: Algal Research, Volume 43Author(s): William J. HenleyAbstractPhotoautotrophic continuous cultures (chemostat, turbidostat or exponential fed-batch operation) of algae began seventy-five years ago in the laboratory and nearly sixty years ago in large-scale outdoor wastewater treatment. Despite this deep and rich history, continuous culture approaches have been used in a small fraction of publications involving algal culturing over the last fifty-five years. Algae grown in continuous cultures are indefinitely in exponential balanced growth, poised at a particular physiological steady state, or a cyclical steady state under a light-dark cycle (cyclostat). This enables mechanistic linking of culture conditions to physiology much more precisely than in batch cultures, where conditions (light, nutrient and possibly CO2 availability), physiological state and specific growth rate change progressively. Continuous cultures also yield consistent biomass composition over time and have the potential to exhibit higher time-averaged biomass production than batch cultures, because growth rate does not decelerate. Commercial algal culture for various products has been studied almost exclusively in batch culture at all scales. The prevailing dogma is that elevated TAG content (the most extensively studied product) occurs only when cell division ceases due to nutrient depletion. Limited recent experimental evidence from continuous cultures suggests that this is not necessarily the case, thus warranting further investigation. Continuous cultures may be particularly useful for customizing biomass composition in favor of desirable high value bioproducts. Innovative continuous culture approaches, including hybrid designs and manipulated steady state, therefore promise to advance basic algal research and, pending scaled-up experimentation, may be useful for commercial biomass production in some contexts. There is insufficient information to date to conclude whether continuous culture (or hybrid) approaches can be commercially successful for any application, thus it is premature to dismiss commercial continuous cultures as impracticable or to assert them as suitable or superior.
       
  • Expression and characterization of human lactoferrin with tandem zinc
           finger protein in Chlamydomonas reinhardtii
    • Abstract: Publication date: November 2019Source: Algal Research, Volume 43Author(s): Xiaonan Pang, Yuxi Tong, Fang Li, Xuan Wei, Xiwen Chen, Jia Liu, Defu ChenLactoferrin (LF) is a naturally occurring iron-binding glycoprotein with a number of biological functions. However, its bioavailability remains a major limitation for clinical applications. In this study, we explored the expression of functional human lactoferrin (hLF) containing tandem zinc finger protein (ZFP) repeats in Chlamydomonas reinhardtii. Codon-optimized ZFPn-hLF fusion genes, where n donates 0, 1, 2, or 3 repeats of ZFP, were transformed into C. reinhardtii CW-15 strain. A total of 23 ZFPn-hLF-expressing clones were obtained. The expression levels of the ZFPn-hLF proteins ranged from 1.97% to 2.32% of the total soluble protein. The expression of ZFPn-hLF proteins did not compromise the proliferation of C. reinhardtii. The recombinant ZFPn-hLFs retained the antibacterial activities toward Escherichia coli and Klebsiella variicola IV-3, and also the antioxidant activities toward DPPH and hydroxyl free radicals. ZFP fusion did not compromise the stability of hLF and enabled efficient internalization of hLF into normal human small intestine cells. Efficiency of the internalization was found to be dependent on the number of tandem ZFPs, incubation time and incubation temperature. Our results indicate that recombinant ZFPn-hLFs expressed in C. reinhardtii promotes the absorption of lactoferrin in human intestinal epithelial cells, and thus provide an effective strategy to enhance the bioavailability of lactoferrin for its utilization in clinical applications.Graphical abstractUnlabelled Image
       
  • Efficient hydrolysis of glycogen from engineered Synechocystis sp. PCC
           6803 catalyzed by recyclable surface functionalized nanoparticles for
           ethanol production
    • Abstract: Publication date: November 2019Source: Algal Research, Volume 43Author(s): Rajendran Velmurugan, Aran IncharoensakdiThe availability of sugars is a key factor for industrial ethanol production. In this study, recyclable surface functionalized metal oxides were prepared and used as catalysts to obtain sugars directly from engineered Synechocystis sp. PCC 6803 (hereafter Synechocystis) biomass. The individual, sulphonated and tungstenated forms of Al2O3, CaO, Fe3O4, TiO2 and ZrO2 were screened for the hydrolysis of Synechocystis glycogen under ultrasound irradiation. Among them, the sulphonated ZrO2 produced a maximum fermentable sugar yield of 40.2 g/L, whereas the tungstenated ZrO2 produced 37.8 g/L. This improvement was due to the combined action of ultrasound irradiation and acidic groups conferred by sulphur or tungsten on metal oxides. In recycling, tungstenated metal oxides were superior to sulphonated metal oxides in terms of recovery and hydrolysis efficiency. The compatibility of the tungstenated metal oxides mediated hydrolysis with fermentation using Saccharomyces cerevisiae MTCC-170 produced the highest ethanol concentration (16.5 g/L), which favors the overall process.Graphical abstractSchematic representation of surface functionalized metal oxide mediated hydrolysis for ethanol production.Unlabelled Image
       
  • Long-term treatment with 9-cis-β-carotene rich alga Dunaliella bardawil
           ameliorates photoreceptor degeneration in a mouse model of retinoid cycle
           defect
    • Abstract: Publication date: November 2019Source: Algal Research, Volume 43Author(s): Victoria Edelshtain, Alon Peled, Adi Tzameret, Sarah Pri Chen, Hana Ziv, Estela Derazne, Dror Harats, Rachel Greenberg, Ayelet Harari, Aviv Shaish, Ifat Sher, Ygal RotenstreichAbstractThe retinoid cycle is the enzymatic pathway that regenerates the vision chromophore, 11-cis retinal, after it is bleached during light absorption. Genetic insults to this cycle result in incurable blinding retinal dystrophies such as retinitis pigmentosa and Leber congenital amaurosis. Previous studies demonstrated that oral treatment with 9-cis-β-carotene rich Dunaliella bardawil powder significantly improved visual and retinal function in patients with fundus albipunctatus night blindness and retinitis pigmentosa. Here we examined the effect of oral treatment with the Dunaliella powder on retinal function and structure in RPE65rd12 mice, a model of a genetic defect in the retinoid cycle. Mice were fed with a control diet, vitamin A deficient diet (VAD) or VAD diet supplemented with Dunaliella powder for 13 months. Mice fed with Dunaliella presented significantly higher dark-adapted (35.7 μV ± 3.1 vs. 6.9 μV ± 2.5, p 
       
  • Harmless disposal and resource utilization of wastes from the lake in
           China: Dewatering, composting and safety evaluation of fertilizer
    • Abstract: Publication date: November 2019Source: Algal Research, Volume 43Author(s): Shiqun Han, Jinlian Li, Qing Zhou, Guofeng Liu, Tao WangRemoval of waste (cyanobacteria, macrophytes and sediment) from Chaohu Lake, a large freshwater lake in China, might cause secondary environmental pollution due to improper disposal. Bioleaching dewatering and composting were performed in this study to dispose these wastes. The results showed that bioleaching could effectively decrease the water content in the cyanobacteria-macrophytes-sediment mixture. The reduced nitrogen-loss rate and increased humus content were observed in the compost after inoculating with microbial agent. High-throughput DNA sequencing showed that the microbial inoculants influenced microbial community composition. The degradation rates of microcystin variant with leucine (MC-LR) and microcystin variant with arginine (MC-RR) in the treatment of composting plus microbial inoculation were significantly higher than those in the natural placement. Seeds of Chinese cabbage were grown in the soil supplemented with mature compost for 67 days. The content of heavy metals in the organic fertilizer, soil and cabbage were much lower than the corresponding limited values of the national standard in China. In conclusion, the cyanobacteria, macrophytes and sediment in China Chaohu Lake could be used safely as raw materials for composting.Graphical abstractUnlabelled Image
       
  • Extraction and purification of eicosapentaenoic acid and docosahexaenoic
           acid from microalgae: A critical review
    • Abstract: Publication date: November 2019Source: Algal Research, Volume 43Author(s): Xiangping Li, Juping Liu, Guanyi Chen, Jianguang Zhang, Chuanbin Wang, Bin LiuAbstractEPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) products have been widely applied due to their medical and healthcare value. In this paper, the methods for extracting DHA and EPA from microalgae and related purification methods were summarized and analyzed. The yields of DHA and EPA from different species of microalgae were investigated. The optimal extraction and purification methods and microalgae species that are suitable for the extraction of EPA and DHA products were determined. Currently, organic solvents are extensively used to extract oil from microalgal biomasses. The supercritical fluid extraction technique is an ideal method for lipid extraction. Based on the findings presented in this paper, a combination of multiple methods is a better choice to extract and purify EPA and DHA from microalgae.
       
  • Enhancing Scenedesmus obliquus biofilm growth and CO2 fixation in a
           gas-permeable membrane photobioreactor integrated with additional rough
           surface
    • Abstract: Publication date: November 2019Source: Algal Research, Volume 43Author(s): Chenglong Guo, Danru Duan, Yahui Sun, Yuying Han, Sha ZhaoAbstractMicroalgae biofilm photobioreactors (PBRs) have been gaining more and more attention worldwide attributed to their advantages of lower water requirement and simpler harvesting process. In this work, aiming at enhancing microalgae biofilm growth and gas-liquid mass transfer based on previous biofilm PBRs, a gas-permeable membrane PBR integrated with additional rough surface (GMPBR-RS) was designed. By attaching an additional piece of stainless steel mesh onto the upper surface of the newly prepared gas-permeable membrane, the roughness of the substratum surface for Scenedesmus obliquus biofilm adhesion was enhanced and therefore resulted in a 28.27% improvement in areal biomass density of S. obliquus relative to the control PBR. Moreover, responses of S. obliquus biofilm adsorption growth and CO2 fixation in the GMPBR-RS to various liquid flow rates and gas flow rates were investigated. Notably, the maximum areal biomass density of S. obliquus biofilm and CO2 removal efficiency of the GMPBR-RS reached 31.44 g m−2 and 65.05%, respectively.
       
 
 
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