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  Subjects -> BIOLOGY (Total: 3126 journals)
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BIOTECHNOLOGY (236 journals)                  1 2 | Last

Showing 1 - 200 of 239 Journals sorted alphabetically
3 Biotech     Open Access   (Followers: 8)
Advanced Biomedical Research     Open Access  
Advances in Bioscience and Biotechnology     Open Access   (Followers: 16)
Advances in Genetic Engineering & Biotechnology     Hybrid Journal   (Followers: 7)
Advances in Regenerative Medicine     Open Access   (Followers: 2)
African Journal of Biotechnology     Open Access   (Followers: 6)
Algal Research     Partially Free   (Followers: 11)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 67)
American Journal of Bioinformatics Research     Open Access   (Followers: 7)
American Journal of Polymer Science     Open Access   (Followers: 32)
Anadolu University Journal of Science and Technology : C Life Sciences and Biotechnology     Open Access  
Animal Biotechnology     Hybrid Journal   (Followers: 8)
Annales des Sciences Agronomiques     Full-text available via subscription  
Applied Biochemistry and Biotechnology     Hybrid Journal   (Followers: 43)
Applied Biosafety     Hybrid Journal  
Applied Food Biotechnology     Open Access   (Followers: 3)
Applied Microbiology and Biotechnology     Hybrid Journal   (Followers: 64)
Applied Mycology and Biotechnology     Full-text available via subscription   (Followers: 4)
Arthroplasty Today     Open Access   (Followers: 1)
Artificial Cells, Nanomedicine and Biotechnology     Hybrid Journal   (Followers: 1)
Asia Pacific Biotech News     Hybrid Journal   (Followers: 2)
Asian Journal of Biotechnology     Open Access   (Followers: 9)
Asian Pacific Journal of Tropical Biomedicine     Open Access   (Followers: 2)
Australasian Biotechnology     Full-text available via subscription   (Followers: 1)
Banat's Journal of Biotechnology     Open Access  
BBR : Biochemistry and Biotechnology Reports     Open Access   (Followers: 5)
Beitr?ge zur Tabakforschung International/Contributions to Tobacco Research     Open Access   (Followers: 2)
Bio-Algorithms and Med-Systems     Hybrid Journal   (Followers: 2)
Bio-Research     Full-text available via subscription   (Followers: 3)
Bioactive Materials     Open Access   (Followers: 1)
Biocatalysis and Agricultural Biotechnology     Hybrid Journal   (Followers: 4)
Biocybernetics and Biological Engineering     Full-text available via subscription   (Followers: 5)
Bioethics UPdate     Hybrid Journal   (Followers: 1)
Biofuels     Hybrid Journal   (Followers: 11)
Biofuels Engineering     Open Access   (Followers: 1)
Biological & Pharmaceutical Bulletin     Full-text available via subscription   (Followers: 4)
Biological Cybernetics     Hybrid Journal   (Followers: 10)
Biomarkers and Genomic Medicine     Open Access   (Followers: 3)
Biomarkers in Drug Development     Partially Free   (Followers: 1)
Biomaterials Research     Open Access   (Followers: 4)
BioMed Research International     Open Access   (Followers: 4)
Biomédica     Open Access  
Biomedical and Biotechnology Research Journal     Open Access  
Biomedical Engineering Research     Open Access   (Followers: 6)
Biomedical Glasses     Open Access  
Biomedical Reports     Full-text available via subscription  
BioMedicine     Open Access  
Biomedika     Open Access  
Bioprinting     Hybrid Journal   (Followers: 1)
Bioresource Technology Reports     Hybrid Journal   (Followers: 1)
Bioscience, Biotechnology, and Biochemistry     Hybrid Journal   (Followers: 21)
Biosensors Journal     Open Access  
Biosimilars     Open Access   (Followers: 1)
Biosurface and Biotribology     Open Access  
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 1)
BioTechniques : The International Journal of Life Science Methods     Full-text available via subscription   (Followers: 28)
Biotechnologia Acta     Open Access   (Followers: 1)
Biotechnologie, Agronomie, Société et Environnement     Open Access   (Followers: 2)
Biotechnology     Open Access   (Followers: 6)
Biotechnology & Biotechnological Equipment     Open Access   (Followers: 4)
Biotechnology Advances     Hybrid Journal   (Followers: 33)
Biotechnology and Applied Biochemistry     Hybrid Journal   (Followers: 44)
Biotechnology and Bioengineering     Hybrid Journal   (Followers: 153)
Biotechnology and Bioprocess Engineering     Hybrid Journal   (Followers: 5)
Biotechnology and Genetic Engineering Reviews     Hybrid Journal   (Followers: 13)
Biotechnology and Health Sciences     Open Access   (Followers: 1)
Biotechnology and Molecular Biology Reviews     Open Access   (Followers: 2)
Biotechnology Annual Review     Full-text available via subscription   (Followers: 5)
Biotechnology for Biofuels     Open Access   (Followers: 10)
Biotechnology Frontier     Open Access   (Followers: 2)
Biotechnology Journal     Hybrid Journal   (Followers: 16)
Biotechnology Law Report     Hybrid Journal   (Followers: 4)
Biotechnology Letters     Hybrid Journal   (Followers: 34)
Biotechnology Progress     Hybrid Journal   (Followers: 40)
Biotechnology Reports     Open Access  
Biotechnology Research International     Open Access   (Followers: 1)
Biotechnology Techniques     Hybrid Journal   (Followers: 10)
Biotecnología Aplicada     Open Access  
Bioteknologi (Biotechnological Studies)     Open Access  
BIOTIK : Jurnal Ilmiah Biologi Teknologi dan Kependidikan     Open Access  
Biotribology     Hybrid Journal   (Followers: 1)
BMC Biotechnology     Open Access   (Followers: 16)
Cell Biology and Development     Open Access  
Chinese Journal of Agricultural Biotechnology     Full-text available via subscription   (Followers: 4)
Communications in Mathematical Biology and Neuroscience     Open Access  
Computational and Structural Biotechnology Journal     Open Access   (Followers: 2)
Computer Methods and Programs in Biomedicine     Hybrid Journal   (Followers: 8)
Copernican Letters     Open Access   (Followers: 1)
Critical Reviews in Biotechnology     Hybrid Journal   (Followers: 20)
Crop Breeding and Applied Biotechnology     Open Access   (Followers: 3)
Current Bionanotechnology     Hybrid Journal  
Current Biotechnology     Hybrid Journal   (Followers: 4)
Current Opinion in Biomedical Engineering     Hybrid Journal   (Followers: 1)
Current Opinion in Biotechnology     Hybrid Journal   (Followers: 56)
Current Pharmaceutical Biotechnology     Hybrid Journal   (Followers: 9)
Current Research in Bioinformatics     Open Access   (Followers: 12)
Current Trends in Biotechnology and Chemical Research     Open Access   (Followers: 3)
Current trends in Biotechnology and Pharmacy     Open Access   (Followers: 8)
EBioMedicine     Open Access  
Electronic Journal of Biotechnology     Open Access  
Entomologia Generalis     Full-text available via subscription  
Environmental Science : Processes & Impacts     Full-text available via subscription   (Followers: 4)
Experimental Biology and Medicine     Hybrid Journal   (Followers: 3)
Folia Medica Indonesiana     Open Access  
Food Bioscience     Hybrid Journal  
Food Biotechnology     Hybrid Journal   (Followers: 9)
Food Science and Biotechnology     Hybrid Journal   (Followers: 8)
Frontiers in Bioengineering and Biotechnology     Open Access   (Followers: 6)
Frontiers in Systems Biology     Open Access   (Followers: 2)
Fungal Biology and Biotechnology     Open Access   (Followers: 2)
GM Crops and Food: Biotechnology in Agriculture and the Food Chain     Full-text available via subscription   (Followers: 1)
GSTF Journal of BioSciences     Open Access  
HAYATI Journal of Biosciences     Open Access  
Horticulture, Environment, and Biotechnology     Hybrid Journal   (Followers: 11)
IEEE Transactions on Molecular, Biological and Multi-Scale Communications     Hybrid Journal   (Followers: 1)
IET Nanobiotechnology     Hybrid Journal   (Followers: 2)
IIOAB Letters     Open Access  
IN VIVO     Full-text available via subscription   (Followers: 4)
Indian Journal of Biotechnology (IJBT)     Open Access   (Followers: 2)
Indonesia Journal of Biomedical Science     Open Access   (Followers: 2)
Indonesian Journal of Biotechnology     Open Access   (Followers: 1)
Indonesian Journal of Medicine     Open Access  
Industrial Biotechnology     Hybrid Journal   (Followers: 17)
International Biomechanics     Open Access  
International Journal of Bioinformatics Research and Applications     Hybrid Journal   (Followers: 13)
International Journal of Biomechatronics and Biomedical Robotics     Hybrid Journal   (Followers: 4)
International Journal of Biomedical Research     Open Access   (Followers: 2)
International Journal of Biotechnology     Hybrid Journal   (Followers: 5)
International Journal of Biotechnology and Molecular Biology Research     Open Access   (Followers: 3)
International Journal of Biotechnology for Wellness Industries     Partially Free   (Followers: 1)
International Journal of Environment, Agriculture and Biotechnology     Open Access   (Followers: 5)
International Journal of Functional Informatics and Personalised Medicine     Hybrid Journal   (Followers: 4)
International Journal of Medicine and Biomedical Research     Open Access   (Followers: 1)
International Journal of Nanotechnology and Molecular Computation     Full-text available via subscription   (Followers: 3)
International Journal of Radiation Biology     Hybrid Journal   (Followers: 4)
Iranian Journal of Biotechnology     Open Access  
ISABB Journal of Biotechnology and Bioinformatics     Open Access  
Italian Journal of Food Science     Open Access   (Followers: 1)
JMIR Biomedical Engineering     Open Access  
Journal of Biometrics & Biostatistics     Open Access   (Followers: 3)
Journal of Bioterrorism & Biodefense     Open Access   (Followers: 6)
Journal of Petroleum & Environmental Biotechnology     Open Access   (Followers: 1)
Journal of Advanced Therapies and Medical Innovation Sciences     Open Access  
Journal of Advances in Biotechnology     Open Access   (Followers: 5)
Journal Of Agrobiotechnology     Open Access  
Journal of Analytical & Bioanalytical Techniques     Open Access   (Followers: 7)
Journal of Animal Science and Biotechnology     Open Access   (Followers: 4)
Journal of Applied Biomedicine     Open Access   (Followers: 2)
Journal of Applied Biotechnology     Open Access   (Followers: 2)
Journal of Applied Biotechnology Reports     Open Access   (Followers: 2)
Journal of Applied Mathematics & Bioinformatics     Open Access   (Followers: 5)
Journal of Biologically Active Products from Nature     Hybrid Journal   (Followers: 1)
Journal of Biomaterials and Nanobiotechnology     Open Access   (Followers: 6)
Journal of Biomedical Photonics & Engineering     Open Access  
Journal of Biomedical Practitioners     Open Access  
Journal of Bioprocess Engineering and Biorefinery     Full-text available via subscription  
Journal of Bioprocessing & Biotechniques     Open Access  
Journal of Biosecurity Biosafety and Biodefense Law     Hybrid Journal   (Followers: 3)
Journal of Biotechnology     Hybrid Journal   (Followers: 64)
Journal of Biotechnology and Strategic Health Research     Open Access  
Journal of Chemical and Biological Interfaces     Full-text available via subscription   (Followers: 1)
Journal of Chemical Technology & Biotechnology     Hybrid Journal   (Followers: 9)
Journal of Chitin and Chitosan Science     Full-text available via subscription   (Followers: 1)
Journal of Colloid Science and Biotechnology     Full-text available via subscription  
Journal of Commercial Biotechnology     Full-text available via subscription   (Followers: 6)
Journal of Crop Science and Biotechnology     Hybrid Journal   (Followers: 3)
Journal of Essential Oil Research     Hybrid Journal   (Followers: 2)
Journal of Experimental Biology     Full-text available via subscription   (Followers: 25)
Journal of Genetic Engineering and Biotechnology     Open Access   (Followers: 5)
Journal of Ginseng Research     Open Access  
Journal of Industrial Microbiology and Biotechnology     Hybrid Journal   (Followers: 17)
Journal of Integrative Bioinformatics     Open Access  
Journal of Medical Imaging and Health Informatics     Full-text available via subscription  
Journal of Molecular Biology and Biotechnology     Open Access  
Journal of Molecular Microbiology and Biotechnology     Full-text available via subscription   (Followers: 11)
Journal of Nano Education     Full-text available via subscription  
Journal of Nanobiotechnology     Open Access   (Followers: 4)
Journal of Nanofluids     Full-text available via subscription   (Followers: 1)
Journal of Organic and Biomolecular Simulations     Open Access  
Journal of Plant Biochemistry and Biotechnology     Hybrid Journal   (Followers: 4)
Journal of Science and Applications : Biomedicine     Open Access  
Journal of the Mechanical Behavior of Biomedical Materials     Hybrid Journal   (Followers: 12)
Journal of Trace Elements in Medicine and Biology     Hybrid Journal   (Followers: 1)
Journal of Tropical Microbiology and Biotechnology     Full-text available via subscription  
Journal of Yeast and Fungal Research     Open Access   (Followers: 1)
Marine Biotechnology     Hybrid Journal   (Followers: 4)
Meat Technology     Open Access  
Messenger     Full-text available via subscription  
Metabolic Engineering Communications     Open Access   (Followers: 4)
Metalloproteinases In Medicine     Open Access  
Microbial Biotechnology     Open Access   (Followers: 9)
MicroMedicine     Open Access   (Followers: 3)
Molecular and Cellular Biomedical Sciences     Open Access   (Followers: 1)
Molecular Biotechnology     Hybrid Journal   (Followers: 13)
Molecular Genetics and Metabolism Reports     Open Access   (Followers: 3)
Nanobiomedicine     Open Access  
Nanobiotechnology     Hybrid Journal   (Followers: 2)
Nanomaterials and Nanotechnology     Open Access  
Nanomedicine and Nanobiology     Full-text available via subscription  
Nanomedicine Research Journal     Open Access  

        1 2 | Last

Journal Cover
Algal Research
Journal Prestige (SJR): 1.142
Citation Impact (citeScore): 4
Number of Followers: 11  
 
  Partially Free Journal Partially Free Journal
ISSN (Online) 2211-9264
Published by Elsevier Homepage  [3161 journals]
  • Purification of phycocyanin from Arthrospira platensis by hydrophobic
           interaction membrane chromatography
    • Abstract: Publication date: November 2018Source: Algal Research, Volume 35Author(s): Rosaria Lauceri, Graziella Chini Zittelli, Biancaelena Maserti, Giuseppe TorzilloThe cyanobacterium Arthrospira platensis is an important source of phycocyanin, which has many commercial applications in foods, cosmetics and pharmaceutics. In this study, hydrophobic interaction membrane chromatography (HIMC) was used for the first time to separate phycocyanin from allophycocyanin and obtain analytical grade phycocyanin, avoiding packed bed (i.e., packed column) chromatography steps. The extraction of phycobiliproteins was carried out on freeze-dried biomass samples suspended in NaCl 0.1 M, and the phycobiliprotein crude extract was obtained by centrifuging the suspension to eliminate cell debris. The crude extract, after the addition of an appropriate amount of ammonium sulphate, was loaded on an ammonium sulphate responsive commercial hydrophilic polyvinylidene fluoride (PVDF) membrane for the HIMC purification process. Applying a two-step HIMC purification procedure, a phycocyanin purity ratio of 4.20 and a yield of 67.0% was attained.Graphical abstractUnlabelled Image
       
  • The effect of high-intensity ultrasound on cell disruption and lipid
           extraction from high-solids viscous slurries of Nannochloropsis sp.
           biomass
    • Abstract: Publication date: November 2018Source: Algal Research, Volume 35Author(s): Shunyu Yao, Srinivas Mettu, Sam Q.K. Law, Muthupandian Ashokkumar, Gregory J.O. MartinThe effect of ultrasonication on the cell rupture of marine microalgae Nannochloropsis sp. was studied as a function of the slurry solids concentration and treatment time. The concentrated viscous wet-biomass (~12 to 25% solids concentration) was subjected to ultrasonication (20 kHz) at 3.8 W/mL for up to 5 min. Compared to extraction without cell rupture, sonication led to a significant increase in lipid yield from ~11% to about 70% within 5 min of sonication. The extraction yield was found to decrease with increased solids concentration, with a large decrease between 20% to 25% solids. This is attributed to the increase in viscosity and decrease in speed of sound with increase in solids. The ultrasound attenuation coefficient increased 320-fold as the solids increased from 20 to 25%. Such a large attenuation of ultrasound places a limit of 20% solids to be used for cell rupture by ultrasound. The specific energy requirements per unit mass of extracted lipid were lowest at 20% solids. At lower concentrations energy was wasted heating water, at higher concentrations the lipid yields were reduced due to ultrasound attenuation.Graphical abstractUnlabelled Image
       
  • Effective in situ harvest of microalgae with bacterial cellulose produced
           by Gluconacetobacter xylinus
    • Abstract: Publication date: November 2018Source: Algal Research, Volume 35Author(s): Qiaohong Chen, Qi Fan, Zexuan Zhang, Yiqiang Mei, Haiying WangAbstractA new biological approach was explored to harvest microalgae in situ with bacterial cellulose produced by Gluconacetobacter xylinus grown in microalgal culture by adding different proportions of glucose/yeast extract (GY) media. This study attempted to optimize this process in terms of GY media concentration, process time, microalgae cell concentration, and oscillation speed. Bacterial cellulose successfully harvested nearly 90% of Scenedesmus obliqnus and Chlamydomonas reinhardtii after only 8 h, and 92% of Chlorella vulgaris after 48 h, with supplementation of 30% (v/v) GY media to the microalgae culture. This method allows harvested media to be recycled instead of GY media, and can be used for a variety of cell densities. Scanning electron microscopy revealed that microalgae cells were harvested after being embedded in a network of bacterial cellulose. These results suggest this effective and simple operation has the potential for developing a cost-effective harvest method for microalgae production.
       
  • Seawater desalination concentrate for cultivation of Dunaliella salina
           with floating photobioreactor to produce β-carotene
    • Abstract: Publication date: November 2018Source: Algal Research, Volume 35Author(s): Chenba Zhu, Xiaoqian Zhai, Ji Jia, Jinghan Wang, Desen Han, Yonghai Li, Yajie Tang, Zhanyou ChiAbstractUsing seawater desalination concentrate to produce microalgae biomass enriched with high value products is a promising way to improve the profitability of desalination industry, but this is seriously limited by enormous land requirement for microalgae farming, as well as high cost of microalgae cultivation. In this study, low cost floating photobioreactor was adopted to cultivate Dunaliella salina to produce β-carotene, using seawater desalination concentrate as culture medium. With carbonate precipitate pretreatment, 97.6% Ca2+ and 60.3% Mg2+ were removed from seawater desalination concentrate. Then, this carbonate enriched medium was bubbled with CO2, to generate bicarbonate, and this increased total inorganic carbon to 0.254 mol L−1. Cultivation with this medium resulted in biomass production without difference from optimized concentrated artificial seawater medium. Pilot scale cultivation of D. salina with floating PBR on ocean showed that 300 g algal biomass containing 14.3 g β-carotene can be produced from 1 m3 desalination concentrate. This amount of β-carotene enriched biomass has a value more than $ 40, and would significantly improve the profitability of desalination industry.
       
  • Performance of a high rate algal pond treating septic tank effluent from a
           community wastewater management scheme in rural South Australia
    • Abstract: Publication date: November 2018Source: Algal Research, Volume 35Author(s): Neil A. Buchanan, Paul Young, Nancy J. Cromar, Howard J. FallowfieldAbstractA high rate algal pond (HRAP) incorporated into a community wastewater management scheme was operated over two years in the Mediterranean climate of Kingston on Murray, South Australia. Uniquely, the study evaluated the performance of the HRAP when fed (12 m3 day−1) either treated effluent from on-site septic tanks or a facultative pond further treating the septic tank effluent from within the community (population 300). The influence of depth and season on wastewater treatment and biomass production were determined for both configurations. Generally, wastewater treatment (>90% BOD5 removed) and biomass production (31.7 g m−2 day−1) was improved when the HRAP was fed septic tank effluent. PO4-P removal was low and effected by biomass uptake rather than precipitation. Inorganic nitrogen removal was independent of depth in the warmer months and inversely related to depth in the colder months. The mean log10 removal values for Escherichia coli were 1.75 and 2.75 for the HRAP when fed septic and facultative pond effluent respectively. In the prevailing Mediterranean climate, adequate BOD5 and nitrogen removal, and disinfection assessed using E. coli as the faecal indicator organism was achieved at 0.32 m depth at a retention time of 4 days.
       
  • Differential growth, yield and biochemical responses of maize to the
           exogenous application of Kappaphycus alvarezii seaweed extract, at
           grain-filling stage under normal and drought conditions
    • Abstract: Publication date: November 2018Source: Algal Research, Volume 35Author(s): Khanjan Trivedi, K.G. Vijay Anand, Pradip Vaghela, Arup GhoshAbstractMaize is sensitive to water stress at flowering and grain-filling stages and thus strategies for the mitigation of stress and improving the yield sustainably would be beneficial. Two factorial pot experiments were carried out to assess the efficacy of a biostimulant product obtained from Kappaphycus alvarezii in conjunction with recommended rate of fertilizers (RRF), in mitigating moderate and severe stress in maize. The plants were subjected to normal as well as water deficit conditions following which Kappaphycus alvarezii seaweed extract (KSWE) was applied foliarly only once at the grain-filling stage along with a suitable control (water spray + RRF). Growth and yield parameters along with antioxidant enzymes, metabolites and reactive oxygen species content in leaves were studied. The results revealed that water deficit conditions (moderate and severe) significantly (p 
       
  • Molecular characterization and atomistic model of biocrude oils from
           hydrothermal liquefaction of microalgae
    • Abstract: Publication date: November 2018Source: Algal Research, Volume 35Author(s): Diego López Barreiro, Francisco J. Martin-Martinez, Cristian Torri, Wolter Prins, Markus J. BuehlerAbstractHydrothermal liquefaction (HTL) converts wet biomass into biocrude oils that can serve as a green substitute to fossil crude oil for several applications, i.e., biofuel or additive for asphalt. However, the use of biocrude oils in such applications has been limited by a lack of detailed characterization of its molecular components. This hinders the establishment of molecular models for biocrude oil that can be used to establish computationally the links between HTL parameters, chemical composition of biocrude, and its macroscopic properties and applications. Understanding such links would significantly reduce the need of expensive and time-consuming trial-and-error HTL experimentation. Here, we present the first molecular model of biocrude oil from microalgae derived from a detailed analytical characterization by pyrolysis gas chromatography mass spectrometry (Py-GC–MS) with non-negative matrix factorization (NNMF), supported by an extensive literature research. The selected molecules are then characterized by conceptual density functional theory (DFT) calculations. These are then used to evaluate the reactivity and intermolecular interactions of biocrude oil in upgrading and oxidative ageing processes, which are the most relevant for its aforementioned application as biofuel or as additive for asphalt. The results show that the properties of the light fraction of biocrude oil favor its use for biofuel. In the case of additive for asphalt pavement, the light fraction is less prone to oxidative ageing, while the heavy fraction might still be useful to provide the rheological properties required for asphalt concrete.
       
  • Laboratory extraction of microalgal lipids using sugarcane bagasse derived
           green solvents
    • Abstract: Publication date: November 2018Source: Algal Research, Volume 35Author(s): Sérgio S. de Jesus, Gabriela F. Ferreira, Leonardo V. Fregolente, Rubens Maciel FilhoAbstractThree green solvents were tested for lipid extraction based on the Bligh and Dyer method. Lipids from the microalgae Chlorella pyrenoidosa were extracted through the tertiary systems 2-methyltetrahydrofuran:isoamylalcohol:water (1:3, 1:2, 1:1, 2:1, 3:1 v/v) and 2-methyltetrahydrofuran:ethanol:water (3:1 v/v). For comparative effect, extractions with chloroform:methanol:water (3:1, 2:1, 1:1, 1:2, 1:3 v/v), with binary systems 2-methyltetrahydrofuran:water, isoamyl alcohol:water, chloroform:water, n-hexane:water, and monophasic systems 2-methyltetrahydrofuran (2-MeTHF), isoamyl alcohol, chloroform and n-hexane were used. The Bligh and Dyer method using green solvents was highly efficient, although some undesirable components were extracted, especially when larger volumes of isoamyl alcohol were used. System 2-MeTHF:ethanol:water formed only a biphasic system when it was used in a 3:1 (v/v) proportion, obtaining 64% of fatty acids. The chloroform:methanol (1:2 v/v) system extracted 122.2 ± 1.9 mg g−1, in which 92.4% consisted of fatty acids. In systems using green solvents, the extractions with the system 2-MeTHF:isoamyl alcohol (2:1 v/v) achieved a 78% selectivity (99.6 ± 7.6 mg g−1of fatty acids) and an 88.2% efficiency when compared with the reference system chloroform:methanol 1:2 (v/v).The fatty acids profile showed that extractions with 2-MeTHF:isoamyl alcohol had higher percentages of fatty acids with low degree of unsaturation, which is ideal for the production of better quality biodiesel. The results obtained suggest that2-MeTHF:isoamyl alcohol (2:1 v/v) can replace the chloroform:methanol system currently used. At an industrial level, this system still requires some technical improvements related to the energy expenditure for solvent evaporation, and at an economic level, the high price of the 2-MeTHF makes the process impracticable compared with hexane.
       
  • A life-stage conflict of interest in kelp: Higher meiospore settlement
           where sporophyte attachment is weak
    • Abstract: Publication date: November 2018Source: Algal Research, Volume 35Author(s): Philip D. Kerrison, Michele S. Stanley, Elaine Mitchell, Liam Cunningham, Adam D. HughesMeiospores of Laminariales macroalgae must select a benthic substratum suitable for their attachment and survival, but also suitable for the development of the sessile sporophyte stage which can grow metres in length. In a controlled four month experiment, meiospores of Saccharina latissima were allowed to settle and develop on twelve different polymer surfaces. Highest meiospore settlement was seen where the attachment force of the developing macroscopic sporophytes was weak (
       
  • Effect of temperature control on green algae grown under continuous
           culture
    • Abstract: Publication date: November 2018Source: Algal Research, Volume 35Author(s): Carolann M. Knutson, Evelyn M. McLaughlin, Brett M. BarneyAbstractThe large-scale cultivation of algae of commercial value requires a variety of important energy-related inputs to achieve the proposed yields required for economic viability. One specific energy input of interest is temperature control and the associated costs of this control, both in terms of initial capital investment and costs associated with continued cooling or heating. In this work, the green algae Neochloris oleoabundans and Scenedesmus dimorphus were grown in tightly-controlled turbidostat-based photobioreactors to determine the potential benefits of temperature control for biomass production of these organisms versus allowing these cultures to experience temperature fluctuations similar to what would be found in uncontrolled, outdoor open ponds or closed bioreactors. The results of these studies indicate stark differences between these two strains, with N. oleoabundans yielding improved growth rates under conditions of stringent temperature control at 22 °C, while S. dimorphus yielded slightly higher growth under conditions where temperature was allowed to fluctuate based on modeled natural temperature profiles. Further analysis reveals that the utilization of non-conventional temperature profiles could enhance growth yields further for N. oleoabundans, allowing it to overcome the detrimental effects of the natural temperature fluctuation. These results and a discussion of the potential for turbidostat-based algal culture growth are presented.
       
  • Comparative assessment of evaporation models in algal ponds
    • Abstract: Publication date: November 2018Source: Algal Research, Volume 35Author(s): Quentin Béchet, Bruno Sialve, Jean-Philippe Steyer, Andy Shilton, Benoit GuieysseThe ability to predict water evaporation from shallow ponds is needed to accurately assess the water demand and costs of microalgae farming. This study assessed the accuracy of seven evaporation models available in the literature against experimental data collected in a raceway algal pond located in Narbonne, France. A theoretical ‘flat-plate’ evaporation model and the “Sartori model” were identified as the most accurate models (errors of 14.2% and 9.2%, respectively, over a period of 274 days). As these two models require the mathematical determination of pond temperature, simulations were performed to determine if pond temperature could be substituted for air temperature to compute yearly evaporation estimates. Unfortunately, assuming that pond temperature was equal to air temperature caused significant inaccuracies on the yearly evaporation (e.g. up to 68% in an arid climate with the Sartori model). High-resolution co-modeling of evaporation and temperature is therefore required for accurate evaporation predictions.Graphical abstractUnlabelled Image
       
  • Comparison between jet and paddlewheel mixing for the cultivation of
           microalgae in anaerobic digestate of piggery effluent (ADPE)
    • Abstract: Publication date: November 2018Source: Algal Research, Volume 35Author(s): Eladl Eltanahy, Sarik Salim, Ashiwin Vadiveloo, Jennifer J. Verduin, Bruno Pais, Navid R. MoheimaniAbstractThere is great need to improve turbulent mixing of microalgae cultures grown in turbid wastewater to ensure efficient use of light and nutrients for higher biomass productivity and nutrient removal rates. In this outdoor study, we compared the turbulent mixing and nutrient removal efficiency of conventional paddlewheel driven raceway ponds (PWP) with customized jet-nozzle raceway pond (JNP) on microalgae grown in undiluted anaerobic digestate of piggery effluent (ADPE). Overall, the concentration of microalgae consisting mainly of Cyanobacteria and Chlorella sp. trended higher in the JNP than the PWP with notable absence of diatoms in JNP. The average percentage of ammonium removal rates were found to be significantly higher in the JNP (36.8% ± 3.93) than the PWP (23.5% ± 4.42). The measured amount of turbulent kinetic energy (TKE), as an indicator of algal movement at eight distinct locations of both ponds, trended higher in the JNP than the PWP, suggesting improved mixing performance with higher shear stress on cultures in the JNP. Based on the higher ammonium removal rates and turbulence mixing, JNP was found to be more efficient for the cultivation of microalgae in ADPE than PWP.
       
  • Flow conditions influence nutrient removal at an artificial lake and a
           drinking water reservoir with an algal floway
    • Abstract: Publication date: November 2018Source: Algal Research, Volume 35Author(s): Zhihao Yan, Patrick C. Kangas, Xin Yuan, Yuehao Chen, Ying Zhang, Ji Li, Yuping Su, Xinjuan Gao, Nengwang ChenTo optimize flow condition of algal turf scrubber (ATS) system for nutrient (nitrogen and phosphorus) removal at eutrophic waterbodies, we constructed two experimental scale (2.5 m2) algal floways to test nutrient removal rates under various flow conditions via regulating flow rate and intermittent frequency of pump on/off. Results showed that the largest algal productivity and nutrient removal rate were generally obtained under the hydraulic loadings of 120 L min−1 m−1. Nutrient removal rate was high with an intermittent inflow 4 h−1, followed by 12 h−1 and 60 h−1. We estimated that a hectare-scale floway system under a flow rate of 120 L min−1 m−1 and intermittent flow 4 h−1 which would have satisfactory performance with affordable investment. This option has the greatest potential for the application of such technology in nutrient pollution abatement while producing bioresources from harvested microalgae.Graphical abstractUnlabelled Image
       
  • Using microalgal communities for high CO2-tolerant strain
           selection
    • Abstract: Publication date: November 2018Source: Algal Research, Volume 35Author(s): Hualong Wang, Fru Azinwi Nche-Fambo, Zhigang Yu, Feng ChenCertain species of microalgae are capable of growing under high concentrations of carbon dioxide (CO2). These microalgae have potential to be used for sequestering CO2 released as industrial pollutants using a phototrophic carbon fixation system. While some CO2-tolerant algal species have been identified from existing algal culture collections, this study explored a community-based approach to enrich and isolate CO2-tolerant microalgae. Meanwhile, we monitored the change of bacterial and microalgal communities during the CO2 enrichment period based on the 16S and 18S rRNA gene sequences. Four different treatments were set up in the laboratory to test the effect of nutrient and CO2 on the natural planktonic community. At the end of the enrichment experiment (17 days), green algae (Chlorophyta), especially Scenedesmus species, dominated the microalgal community when the water samples were enriched with high CO2 (10%) and nutrient. The dominance of species in the CO2-enriched samples was also evident in the clonal isolation of microalgae at the end of the experiment. This study clearly demonstrates that the supplementation of high levels of CO2 to a natural phytoplankton community is an efficient way to enrich and isolate CO2-tolerant microalgae. The community-based approach described here poses several advantages over the traditional culture-based screening method for isolating microalgae with specific characteristics.Graphical abstractUnlabelled Image
       
  • Thermosynechococcaceae as a source of thermostable C-phycocyanins:
           properties and molecular insights
    • Abstract: Publication date: November 2018Source: Algal Research, Volume 35Author(s): Yuanmei Liang, Michal B. Kaczmarek, Agnieszka K. Kasprzak, Jie Tang, Md. Mahfuzur Rahman Shah, Peng Jin, Anna Klepacz-Smółka, Jay J. Cheng, Stanisław Ledakowicz, Maurycy DarochAbstractThis study describes characterisation of three thermophilic strains of cyanobacteria belonging to Thermosynechococcaceae and their utilisation as a source of thermostable C-phycocyanin. Three strains NIES 2133, NIES 2134 and PCC 6715 have been cultivated in two types of growth media and two temperatures: 45 and 50 °C and assessed for C-phycocyanin productivity. Among these strains Synechococcus lividus sp. PCC 6715, phylogenetically closer to Thermosynechococcus sp. clade than other Synechococcaceae, has been selected for subsequent study to characterise its C-phycocyanin. The strain showed faster growth rates than the other two and appeared to utilise different bicarbonate uptake mechanism based on SbtA, whilst BCT1 mechanism was found in NIES2133 and 2134. Higher growth rates translated to larger overall C-phycocyanin productivity. C-phycocyanin has been purified using chromatographic methods and its thermostability and pH stability has been assessed against that of Spirulina. Results have shown that PCC 6715 C-phycocyanin is one of the most stable proteins of this type reported to date. It exhibits 90% stability after 5-hour incubation at 50 °C and about 70% stability after 2-week incubation at the same temperature. PCC 6715 phycocyanins show high stability at acidic pH at both 4 °C and 50 °C, whilst at 50 °C maintain 100% stability during 4-hour incubation at pH 4.0 to 8.0. PCC 6715 phycocyanin shows good long-term stability characteristics and could be considered as a thermostable replacement for Spirulina phycocyanin. Analysis of molecular model of PCC 6715 C-phycocyanins and crystal structures of other phycocyanins reveals interesting pattern of amino acid substitutions that are present in thermophilic proteins that could have significant impact on their significantly higher thermostability. Phycocyanins from thermostable cyanobacteria exhibit evolutionarily conserved amino acid substitutions localised in the single structural hotspot of the protein that result in additional stabilising interactions within and between protein subunits when compared to proteins from mesophilic counterparts.
       
  • Blue light enhances astaxanthin biosynthesis metabolism and extraction
           
    • Abstract: Publication date: November 2018Source: Algal Research, Volume 35Author(s): Ruijuan Ma, Skye R. Thomas-Hall, Elvis T. Chua, Eladl Eltanahy, Michael E. Netzel, Gabriele Netzel, Yinghua Lu, Peer M. SchenkHaematococcus pluvialis accumulates large amounts of astaxanthin during its haematocyst stage. Cyst germination is a biological pretreatment method for improved astaxanthin extraction with potential to replace energy-intensive homogenizer-based mechanical cell cracking methods. The present study demonstrates effects of different LED light wavelengths on haematocyst germination and on its astaxanthin biosynthesis pathway. Blue light enhanced the germination efficiency and slowed the nitrogen consumption rate, resulting in significantly higher astaxanthin content and improved extractability compared with white and red lights, that also had lower germination rates. After 5 days, the total astaxanthin extractability under blue light was 4.0 and 6.7 times higher than for white and red lights, respectively. The blue light receptor gene phot was significantly induced which upregulated the biosynthesis pathway genes psy and pds, as well as dgat1 and dgat2d. Hence, blue light triggers germination and astaxanthin biosynthesis, providing a strategy for improved extraction while modulating higher biosynthesis during germination.Graphical abstractBlue light increases Haematococcus pluvialis astaxanthin contents, cyst germination efficiency, astaxanthin extractability, and also regulates the astaxanthin biosynthesis pathway.Unlabelled Image
       
  • Response to wound-activated stress through a lipid oxidative metabolic
           pathway in Pyropia haitanensis
    • Abstract: Publication date: November 2018Source: Algal Research, Volume 35Author(s): Juanjuan Chen, Yu Chen, Rui Yang, Qijun Luo, Haimin Chen, Jilin Xu, Xiaojun Yan, Baochun ShenPyropia haitanensis inhabits the intertidal zone and is affected by rough waves and sediment, as well as herbivore-induced and mechanical damage. However, the mechanisms of P. haitanensis response to wounding have not been elucidated. Lipid metabolism is an important defense mechanism in algae, and the lipid defense strategy of P. haitanensis elicited by wound-activated stress was investigated in this study. P. haitanensis was damaged by cutting and allowed to recover for 30 and 60 min. Release of H2O2 that was stimulated by wounding could act as a primary signal to induce phospholipase A2 activation, which catalyzes the degradation of membrane lipids to release free fatty acids. Then, several polyunsaturated fatty acids (C18:2, C20:4 and C20:5) were oxidized by PhLOXs, resulting in decreased polyunsaturated fatty acid levels and increased oxylipins, which were further transformed into short-chain volatile organic compounds. Moreover, increased jasmonic acid levels were also detected after wounding, indicating that the jasmonic acid pathway may also be involved in the defense response of P. haitanensis to wounding, similar to higher plants. Hence, the oxidative lipid metabolic pathway elucidated herein offers plausible physiological insights into lipid metabolism in P. haitanensis in response to wound-activated stress and may facilitate efficient development and improvement of Pyropia quality by producing cultivars resistant to wounding.Graphical abstractUnlabelled Image
       
  • Development of potential yield loss indicators to assess the effect of
           seaweed farming on fish landings
    • Abstract: Publication date: November 2018Source: Algal Research, Volume 35Author(s): Nils Préat, Marleen De Troch, Sonja van Leeuwen, Sue Ellen Taelman, Steven De Meester, Florent Allais, Jo DewulfIn recent years, several indicators have been proposed to assess the effect of human activities on ecosystems provisioning capacity. Some of these methods focus on the Net Primary Production (NPP) available for ecosystem functioning through the comparison between the Human Appropriated Net Primary Production (HANPP) and the ecosystem's initial NPP at a given reference year. While some approaches have been proposed for marine ecosystems, most of the HANPP studies focus on terrestrial systems. This study highlights the relation between the HANPP methods and the production of natural resources in marine ecosystems. The linkage between current overfishing and future fish provisioning (ecosystem service) is well known. However, less studied before, is the relation between seaweed aquaculture and fish provisioning through the marine food web. Seaweed growth requires nutrients and light that will consequently be no longer available for natural phytoplankton production. As seaweed is periodically harvested, a fraction of the ecosystem's NPP (HANPP) is no longer available for ecosystem production. The HANPP of aquaculture reduces the ecosystem carrying capacity and thus affects commercial fish stocks. Therefore, an integrative approach is proposed in this study to assess the potential effect of seaweed farming on fish landings in the Greater North Sea. Three indicators are proposed to assess the Lost Potential Yield (LPY) in fish landings: LPYB, LPYV and LPYE, accounting respectively for reduction in biomass, monetary value and eco-exergy. For these three aspects, the LPY results remains smaller than the seaweed production, meaning that the overall natural resources balance for seaweed farming is positive.Graphical abstractUnlabelled Image
       
  • Process for selective extraction of pigments and functional proteins from
           Chlorella vulgaris
    • Abstract: Publication date: November 2018Source: Algal Research, Volume 35Author(s): Sayali Kulkarni, Zivko NikolovExtraction of multiple high-value products is recommended for sustainability of the microalgal production platform. This study proposes a process for selective extraction of carotenoids and chlorophylls with ethanol, followed by alkaline pH extraction of proteins from wet, freeze-thawed Chlorella vulgaris biomass. A biomass-to-solvent ratio of 1:5 and 3 extraction stages were required to achieve maximum extraction yield of chlorophylls and carotenoids. The main compounds in the ethanol extract were identified as lutein, chlorophyll a and chlorophyll b. The lutein and total chlorophyll yield in the extracts were 5.4 mg/g and 15.4 mg/g dry biomass respectively. Effective protein release from freeze-thawed biomass was contact-time dependent and>76% of total protein could be extracted in 15 min via bead-milling, and in 6 min by high-pressure homogenization at 15000 psi. Ethanol extraction of pigments affected protein solubility, and an alkaline pH was required to release the same total protein. Concentration and fractionation of proteins was carried out using a two-stage membrane filtration process and 78–80% of proteins remained in the 300 kDa retentate. Ethanol treatment and higher pH conditions did not negatively impact membrane filtration, nutritive value, or the emulsification properties of protein concentrates.Graphical abstractUnlabelled Image
       
  • Microwave-assisted extraction of polysaccharides from Arthrospira
           (Spirulina) platensis using the concept of green chemistry
    • Abstract: Publication date: November 2018Source: Algal Research, Volume 35Author(s): Amanda de Sousa e Silva, Weuller Teixeira de Magalhães, Laís Marques Moreira, Maria Valderez Ponte Rocha, Ana Karine Pessoa BastosThe microalgae Spirulina (Arthrospira) platensis has captured attention in the biotechnology field, containing in its composition mainly proteins, carbohydrates, lipids and pigments that are compounds of interest in food, pharmaceutical and cosmetic industries. Branched polysaccharides are the most important among the polymeric components since this microalga and its extraction usually involve high costs with energy and toxic solvents. In this context, the aim of this work was to evaluate the efficiency of obtaining polysaccharides from microalgae A. platensis by a microwave-assisted process, using water as a solvent, following the principles of green chemistry, mainly solvent and energy saving. Different parameters were evaluated: extraction time (1 min of extraction in the microwave was fixed and a contact time of the microalgae with water after the exposure to the microwaves was studied - 0, 20, 40 and 60 min), microwave power (186, 310, 434, 558 and 620 W) and the biomass:solvent ratio (1:15, 1:25, 1:30, 1:35 and 1:45 w·v−1). The optimum extraction condition was obtained using only a treatment in the biomass for 20 min, to remove pigments and lipids before the extraction that was conducted in a microwave power of 434 W for 1 min, biomass:solvent ratio 1:30 w·v−1 and no further contact, obtaining 127 ± 5 mg of carbohydrate/g of biomass. Purified polysaccharide was composed of major glucose and rhamnose, a biomolecule very important given that it has wide applications in medical and food industries.Graphical abstractUnlabelled Image
       
  • Application of the distributed activation energy model to the kinetic
           study of pyrolysis of Nannochloropsis oculata
    • Abstract: Publication date: November 2018Source: Algal Research, Volume 35Author(s): Daniel Viju, Ribhu Gautam, R. VinuPyrolysis of algae is a promising route to produce high quality bio-oil and renewable chemicals. Owing to its complex structural composition, multiple pseudo-components are required to describe its thermal decomposition in a wide temperature range and evaluate the reaction kinetics. In this study, the pyrolysis behavior of the microalga, Nannochloropsis oculata (N. oculata), was studied by means of a thermogravimetric analyzer at various heating rates. A four-parallel-reaction scheme characterizing the pyrolysis of carbohydrate, protein, lipid and the secondary decomposition of char was employed to model thermal degradation using distributed activation energy model (DAEM). The average and standard deviation of activation energy, pre-exponential factor, and composition of the model components for pyrolysis of N. oculata were estimated. The model mass loss and differential mass loss profiles matched well with the experimental data at different heating rates. Based on the model predictions, the decomposition of proteins, carbohydrates, lipids and char occurred in the temperature regimes of 200–450 °C, 200–300 °C, 400–500 °C, and 750–900 °C, respectively. To gain valuable insights on the pyrolysate composition at various temperature regimes, analytical pyrolysis-gas chromatography/mass spectrometry experiments were performed. Indole and phenol, aliphatic and aromatic hydrocarbons, and long chain oxygenates were observed as the major pyrolysates in the temperature regimes of 30–350 °C, 350–600 °C and 600–1000 °C, respectively.Graphical abstractUnlabelled Image
       
  • Detailed biochemical and morphologic characteristics of the green
           microalga Neochloris oleoabundans cell wall
    • Abstract: Publication date: November 2018Source: Algal Research, Volume 35Author(s): Behzad Rashidi, Luisa M. TrindadeAbstractChlorophyta, the group of green algae of which there are>6000 species, manifests a great diversity of intercellular and extracellular components. Building blocks in the cell walls of Chlorophyta are very distinct and they may contain various components. Here, we characterize the cell walls of Neochloris oleoabundans, a Chlorophyte microalga, both in terms of biochemical composition and morphology. N. oleoabundans cell walls are composed of about 24.3% carbohydrates, 31.5% proteins, 22.2% lipids and 7.8% inorganic material, which contrasts to the cell walls of (higher) terrestrial plants in which carbohydrates are by far the main component. We also observed that cell wall carbohydrates are mainly non-cellulosic polysaccharides, essentially composed of rhamnose, galactose, glucuronic acid and glucosamine, of which glucose is only a minor component. The lipids comprising the N. oleoabundans cell walls are generally wax/cutin-like. Electron microscopic studies revealed that N. oleabundans cell walls are approximately 200 nm thick and consist of two main layers: a thinner inner layer and a more electron-dense outer layer. On the outer layer are hair-like structures that are possibly rich in carbohydrates. These findings are an important contribution that enable us to understand the complexity of cell walls in green microalgae.
       
  • Subarctic microalgal strains treat wastewater and produce biomass at low
           temperature and short photoperiod
    • Abstract: Publication date: November 2018Source: Algal Research, Volume 35Author(s): Lorenza Ferro, András Gorzsás, Francesco G. Gentili, Christiane FunkIn Northern countries, microalgal-based processes are challenging due to low light and temperature conditions during a significant part of the year. Three natural strains from Northern Sweden (Chlorella vulgaris, Scenedesmus sp., Desmodesmus sp.) and a collection strain (Scenedesmus obliquus UTEX 417) were cultured in municipal wastewater, comparing their performances, biomass composition and nutrients removal under continuous light at standard (25 °C) and low temperature (5 °C), short photoperiod (3 h light, 25 °C), or moderate winter conditions (6 h light, 15 °C). Only the natural strains grew at low temperature, highly consuming total nitrogen and phosphate (>80% and>70%, respectively) even during cold- and dark-stress. At reduced growth rates, C. vulgaris and Scenedesmus sp. produced similar amounts of biomass (>1 g/l) as in standard conditions. Scenedesmus sp. and Desmodesmus sp. showed phenotypic plasticity and increased carbohydrate content. Short photoperiod strongly reduced growth rates, biomass and storage compounds and induced flocculation in C. vulgaris.Graphical abstractUnlabelled Image
       
  • Study of soil cyanobacteria along a rural-urban gradient
    • Abstract: Publication date: November 2018Source: Algal Research, Volume 35Author(s): Pradeep Kumar Rai, Anuradha Rai, Naveen Kumar Sharma, Surendra SinghAbstractUrbanization is one of the modern and critical factors adversely affecting global biodiversity. The impact of urbanization on soil microbial diversity has sporadically been studied of cyanobacterial diversity. The present study analyzes morphological as well as molecular diversity of cyanobacteria along a rural-urban gradient using a culture based approach. In total, 22 cyanobacterial morphotypes (14 genera and 21 species) from five orders were reported; dominated by the members of the order Nostocales. In general, cyanobacterial diversity decreased from rural to urban areas; with N2-fixing heterocystous forms dominating the cyanobacterial flora of the urban area. The values of Shannon–Weaver (2.56) and Simpson's (2.32) indices suggested higher cyanobacterial diversity in the rural area compared to that of the sub-urban and urban areas. Statistical analyses established the importance of physico-chemical factors in structuring the cyanobcaterial communities along the gradient with soil characteristics such as – pH, organic carbon, nitrogen and bulk density, directly as well as indirectly.
       
  • Proposal of a new thraustochytrid genus Hondaea gen. nov. and comparison
           of its lipid dynamics with the closely related pseudo-cryptic genus
           Aurantiochytrium
    • Abstract: Publication date: November 2018Source: Algal Research, Volume 35Author(s): Younès Dellero, Olivier Cagnac, Suzanne Rose, Khawla Seddiki, Mathilde Cussac, Christian Morabito, Josselin Lupette, Riccardo Aiese Cigliano, Walter Sanseverino, Marcel Kuntz, Juliette Jouhet, Eric Maréchal, Fabrice Rébeillé, Alberto AmatoAbstractThraustochytrids are marine protists highly ecologically relevant in mangrove environments. The family Thraustochytriaceae underwent profound taxonomical rearrangements in the last decade, with the description and emendation of several genera. Here, we identified two new thraustochytrid strains (CCAP 4062/1 and CCAP 4062/3) collected from the same mangrove environment in Mayotte Island (Indian Ocean) and representative of two sister clades in the phylogenetic Aurantiochytrium super clade. Phylogenomic (on 2389 genes) and phylogenetic analyses on 18S rDNA sequences led us to propose the description of a new genus, Hondaea gen. nov. (CCAP 4062/3), closely related and pseudo-cryptic to Aurantiochytrium (CCAP 4062/1). Compared to Aurantiochytrium, Hondaea did not produce amoeboid cells and its zoospores were smaller. Chemotaxonomical traits, such as fatty acid, sterol, and carotenoid profiles measured along the growth curves, validated the new genus description. Genome sequencing and manual annotation of lipid metabolism genes revealed similar pathways in both strains. However, such pathways showed different dynamics during the growth phases. Aurantiochytrium accumulated carotenoids (canthaxanthin) and large amounts of triacylglycerols enriched in ω3-docosahexaenoic acid in the stationary phase, while squalene and free cholesterol increased during the early exponential phase. In contrast, Hondaea accumulated low amounts of triacylglycerols enriched in odd and saturated fatty acids during the early exponential phase, whereas free-sterol and carotenoid contents were little affected. These results suggest that these genera evolved independently, although phylogenetically and ecologically closely related. This comparative study also showed that the biotechnological potential of thraustochytrids cannot be deduced solely from phylogenetic and genomic analyses.
       
  • Sustainable microalgae cultivation by using anaerobic centrate and biogas
           from anaerobic digestion
    • Abstract: Publication date: November 2018Source: Algal Research, Volume 35Author(s): Dingnan Lu, Xiaoqi (Jackie) Zhang, Xiao Liu, Lin Zhang, Mark HinesAbstractThis research was conducted to determine the effectiveness of using biogas generated from the anaerobic digestion of septic tank sludge and its anaerobic centrate on microalgal cultivation. Three types of sparging gas (biogas, air, and nitrogen gas) and two culture media (anaerobic centrate and Bold Basal Medium) were used to generate six different experimental settings. The most microalgal growth of 1074 mg VSS/L was achieved when both biogas and anaerobic centrate were used after 10 days of cultivation at 30 °C. In addition, the anaerobic centrate used had a reduction of 89% in its soluble chemical oxygen demand, a 97.3% reduction in the phosphorus concentration, and a 71.5% reduction in the nitrogen concentration. The results demonstrated tremendous benefits of biogas reuse and anaerobic centrate reclamation via microalgae cultivation.
       
  • Simulation study on comparison of algal treatment to conventional
           biological processes for greywater treatment
    • Abstract: Publication date: November 2018Source: Algal Research, Volume 35Author(s): Arun K. Vuppaladadiyam, Noemi Merayo, Angeles Blanco, Jingwei Hou, Dionysios D. Dionysiou, Ming ZhaoThe reuse of greywater is a promising strategy to preserve fresh water resources for future generations. The main objective of the present study is to simulate three different biological treatment technologies (high rate algal pond (HRP), conventional activated sludge (AS) treatment and rotating biological contactors (RBC)) at varying pollutant loadings (low, medium and high-strength polluted greywater) and, then, compare the treatment efficiency of HRP treatment with both RBCs and AS process. All of the adopted technologies were found to produce effluents with satisfactory quality. RBC achieved higher removal of nitrate and phosphorus compared to the conventional AS treatment process, whereas sensitivity analyses reveal that the AS process reached the steady state condition faster than the RBC process. The removal efficiency for AS process was 100% for biochemical oxygen demand, while the total suspended solids and Escherichia coli concentrations were lower than 5 mg L−1 and 0.001 MPN 100-mL−1, respectively. Algal ponds treatment is effective but highly variable. However, it had additional benefits such as CO2 assimilation and biomass production. The treatment efficiency of algal system depended mainly on the mass concentrations of algae and flow rates. Algae mass concentration of 700 g m−3 and flow rate of 40 m3 d−1 achieved complete removal of the SBOD. The influence of operational parameters on the production of algal biomass was investigated and the higher CO2 fixation efficiency was achieved with the fraction of photoperiod as 0.8 and mass concentration of algae 1000 g m−3.Graphical abstractUnlabelled Image
       
  • Analysis of mass transfer capacity in raceway reactors
    • Abstract: Publication date: November 2018Source: Algal Research, Volume 35Author(s): M. Barceló-Villalobos, J.L. Guzmán Sánchez, I. Martín Cara, J.A. Sánchez Molina, F.G. Acién FernándezAbstractIn the present work, a methodology is proposed to determine the mass transfer capacity in existing microalgae raceway reactors to minimize excessive dissolved oxygen accumulation that would otherwise reduce biomass productivity. The methodology has been validated using a 100 m2 raceway reactor operated in semi-continuous mode. The relevance of each raceway reactor section was evaluated as well as the oxygen transfer capacity in the sump to different air flow rates. The results confirm that dissolved oxygen accumulates in raceway reactors if no appropriate mass transfer systems are provided. Therefore, mass transfer in the sump is the main contributor to oxygen removal in these systems. The variation in the volumetric mass transfer coefficient in the sump as a function of the gas flow rate, and therefore the superficial gas velocity in the sump, has been studied and modelled. Moreover, the developed model has been used to estimate the mass transfer requirements in the sump as a function of the target dissolved oxygen concentration and the oxygen production rate. The proposed methodology allows us to determine and optimize the mass transfer capacity in the sump for any existing raceway reactor. Moreover, it is a powerful tool for the optimization of existing reactors as well as for the design optimization of new reactors.
       
  • Behavior of Euglena gracilis under simultaneous competing optical
           and chemical stimuli
    • Abstract: Publication date: November 2018Source: Algal Research, Volume 35Author(s): Kazunari Ozasa, June Won, Simon Song, Mizuo MaedaAbstractIn this study, we developed a microfluidic system to elucidate the behavioral response of Euglena gracilis cells to simultaneous competing optical and chemical stimuli. The system illuminated a nonuniform blue light of 0.5–18 mW/cm2 on cells confined in a 2D microchamber to induce a photophobic response (step-up photo-shock). After cells accumulated in areas of weak blue light, a CO2 gradient (0%–100%) was generated in the microchamber to induce counter chemotaxis (aerotaxis). E. gracilis cells showed negative chemotaxis for areas of higher CO2 concentrations rather than strong blue light, suggesting that CO2 chemotaxis is dominant over blue light photophobicity. We also examined phototaxis instead of photo-shock responses, using in-plane uniform blue light illumination in a counter direction to the CO2 gradient. The cells exhibited both CO2 chemotaxis and blue light phototaxis, and swam back and forth randomly. In both cases, some sensitive cells accumulated in niche areas, primarily with CO2 concentration 
       
  • Spontaneous mutation rate as a source of diversity for improving desirable
           traits in cultured microalgae
    • Abstract: Publication date: November 2018Source: Algal Research, Volume 35Author(s): Marc Krasovec, Sophie Sanchez-Brosseau, Nigel Grimsley, Gwenael PiganeauAbstractMutations are the main origin of the biodiversity and biological innovations across the tree of life. The number of mutations in a population depends of the mutation rate, noted μ, a key parameter for understanding the evolutionary and adaptive capacity of a species. New mutations are submitted to selection and drift and their probability of fixation in a population depends on their advantageous, deleterious or neutral fitness effect. This process occurs in natural populations, but also in any lab cultures. In this context, the role of spontaneous mutations in the generation of genetic diversity in cultured algae has so far been overlooked, despite its influence on the acquisition and maintenance of desirable phenotypic traits. Several algal species that have a high biotechnological potential, such those producing high-value molecules, might be improved by domestication and oriented selection by experimental evolution. Here, we provide the first estimation of the spontaneous mutation rate, μ, in Picochlorum costavermella (Trebouxiophyceae), a green alga with many potential biotechnological applications. Its spontaneous mutation rate is μ = 10.12 × 10−10 (CI Poisson distribution, μ = 6.3–15.4 × 10−10) mutations per nucleotide per genome per generation. This is one of the highest mutation rates reported for a unicellular eukaryote.
       
  • Conversion of biowaste leachate to valuable biomass and lipids in mixed
           cultures of Euglena gracilis and chlorophytes
    • Abstract: Publication date: November 2018Source: Algal Research, Volume 35Author(s): Marika Tossavainen, Neha Katyal Chopra, Silja Kostia, Kalle Valkonen, Anil K. Sharma, Suvigya Sharma, Anne Ojala, Martin RomantschukMicroalgae are a sustainable alternative for production of valuable omega −3 fatty acids (FAs), but high production costs limit commercialization. Utilization of waste as a nutrient source increases the economics of the cultivation process. Additionally, using mixed algal cultures instead of monocultures makes the cultivation process more flexible and can increase biomass and lipid production. Here, the growth and lipid production of microalgae Euglena gracilis, Selenastrum sp. and, Chlorella sorokiniana were studied in mono- and mixed cultures in small and pilot scale experiments in biowaste leachate. In pilot scale, also nutrient reduction and the number of bacteria were analyzed. Biomass production in the most productive mixed cultures was similar, but not higher than in most productive monocultures. The lipid production was highest in the small-scale monoculture of Selenastrum (10.4% DW) and in the pilot scale culture of Selenastrum with E. gracilis (11.1% DW). The content of alpha-linolenic acid (ALA) increased and eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) remained stable during the cultivation period in all pilot scale cultures. However, increases in biomass and lipid production toward the end of the cultivation resulted in higher EPA and DHA yields in the well growing monoculture of E. gracilis and in the mixed culture of E. gracilis with Selenastrum. Co-cultivation of E. gracilis and Selenastrum also had a positive influence on nutrient uptake and resistance against bacteria. This type of mixed culture may be a good option for commercialization. However, as shown here, minor changes in cultivation conditions can rapidly result in dominance of a subdominant strain, and thus the stability of strain performance and production of desired FAs needs further investigation.Graphical abstractUnlabelled Image
       
  • Metabolomic profiles of tropical Chlorella and Parachlorella species in
           response to physiological changes during exponential and stationary growth
           phase
    • Abstract: Publication date: November 2018Source: Algal Research, Volume 35Author(s): Vejeysri Vello, Shivshankar Umashankar, Siew-Moi Phang, Wan-Loy Chu, Phaik-Eem Lim, Abdul Majid Nazia, Kan-Ern Liew, Sanjay Swarup, Fook-Tim ChewAbstractChlorella species are known to be potential algal candidates for biodiesel production due to their ability to store high lipid content and their natural metabolic versatility. An understanding of physiology and metabolic capacity of indigenous Chlorella strains is potentially useful for future biodiesel production in the tropical environment. The primary aim of this study was to assess the photosynthetic performance, biochemical content and fatty acid composition of Chlorella and Parachlorella species grown and harvested during exponential (EX) and stationary (STA) growth phases in batch culture. Physiological data suggested that the cells responded to these conditions by initiating lipid accumulation when growing from EX to STA phase. An increase of lipid and saturated fatty acids (SFA) contents was observed in STA, although this trend was not consistent across the different strains of Chlorella and Parachlorella species. To gain further insights into metabolomic adaptation at different growth phases, metabolites were extracted from selected Chlorella and Parachlorella strains at EX and STA phase. These metabolic profiles were analysed resulting in identification of 74 metabolites. Metabolomic profiles of Parachlorella showed that there was an increase in recycling of amino acids and nucleic acids at STA phase. The metabolites associated with photosynthesis and chlorophyll biosynthesis were also repressed while carbon sources were channelled into lipid biosynthesis. Meanwhile, Chlorella species showed a similar response in carbon allocation for lipid accumulation with lesser influence on amino acid and chlorophyll degradation. Therefore, Chlorella and Parachlorella species exhibit different changes in metabolic responses at different growth phases, which may be the result of metabolic adaptations arising from their evolutionary plasticity. Overall, our results expand the current understanding of metabolomics of Chlorella and Parachlorella species and provide valuable insights into their lipid accumulation during different stages, which is important for optimization of lipid productivity for biodiesel production.
       
  • Microalgae research worldwide
    • Abstract: Publication date: November 2018Source: Algal Research, Volume 35Author(s): Jose Antonio Garrido-Cardenas, Francisco Manzano-Agugliaro, Francisco Gabriel Acien-Fernandez, Emilio Molina-GrimaAbstractIn this paper, worldwide research trends in the microalgae field are analyzed based on a bibliometric study. We have reviewed the number of publications and their distribution, as well as the most relevant journals and keywords, to determine the evolution and latest tendencies in this field. The results confirm that this is a fast-growing area in terms of the number of publications. The most relevant journals on this subject are Bioresource Technology and Algal Research. Although the majority of papers come out of the USA, the institutions with larger number of publications are actually located in China, France and Spain. The most frequently cited strains are Chlorella and Chlamydomonas. The main keywords that appear in over 1000 articles are generally related to microalgae cultivation applications such as ‘biomass, biofuel, and lipids’ while others are related to the methodology; for instance, ‘bioreactor’. Of all the keywords, ‘biomass’ stands out, as it appears in almost 20% of publications. Bibliographic analysis confirms that Microalgae Biotechnology is a very active field, where scientific productivity has exponentially increased over recent years in tandem with industrial production. Therefore, expectations are high in this field for the near future.
       
  • Orchestration of transcriptome, proteome and metabolome in the diatom
           Phaeodactylum tricornutum during nitrogen limitation
    • Abstract: Publication date: November 2018Source: Algal Research, Volume 35Author(s): Ilse M. Remmers, Sarah D'Adamo, Dirk E. Martens, Ric C.H. de Vos, Roland Mumm, Antoine H.P. America, Jan H.G. Cordewener, Linda V. Bakker, Sander A. Peters, René H. Wijffels, Packo P. LamersAbstractNitrogen deprivation increases the triacylglycerol (TAG) content in microalgae but also severely decreases the growth rate. Most approaches that attempted to increase TAG productivity by overexpression or knockdown of specific genes related to the regulation of the lipid synthesis have reported only little success. More insight into the molecular mechanisms related to lipid accumulation and impaired growth rate is needed to find targets for improving TAG productivity. By using the emerging “omics” approach, we comprehensively profiled the physiology, transcriptome, proteome and metabolome of the diatom Phaeodactylum tricornutum during steady state growth at both nitrogen limited and replete levels during light:dark cycles. Under nitrogen limited conditions, 22% (2699) of the total identified transcripts, 17% (543) of the proteins and 44% (345) of the metabolites were significantly differentially regulated compared to nitrogen replete growth conditions. Although nitrogen limitation was responsible for the majority of significant differential transcript, protein and metabolite accumulation, we also observed differential expression over a diurnal cycle. Nitrogen limitation mainly induced an upregulation of nitrogen fixation, central carbon metabolism and TCA cycle, while photosynthetic and ribosomal protein synthesis are mainly downregulated. Regulation of the lipid metabolism and the expression of predicted proteins involved in lipid processes suggest that lipid rearrangements may substantially contribute to TAG distribution. However, TAG synthesis is also limited by the reduced carbon flux through central metabolism. Future strain improvements should therefore focus on understanding and improving the carbon flux through central carbon metabolism, selectivity and activity of DGAT isoforms and lipase enzymes.
       
  • Cell disruption by cationic surfactants affects bioproduct recovery from
           Synechocystis sp. PCC 6803
    • Abstract: Publication date: September 2018Source: Algal Research, Volume 34Author(s): YenJung Sean Lai, Yun Zhou, Everett Eustance, Levi Straka, Zhaocheng Wang, Bruce E. RittmannAbstractCationic surfactants can be used to improve extraction of high-value products from microalgae, but the best way to apply cationic surfactants has not been established. We evaluated the impacts of contact time and concentration for two cationic surfactants – dodecyltrimethylammonium bromide (DTAB) and hexadecyltrimethylammonium bromide (CTAB) – on extraction of lipids and nonpolar pigments, carotenoids and chlorophyll a, from Synechocystis sp. PCC 6803. For the most dose-effective concentration, pigment extraction was better with the longer alkyl-chain length, i.e., CTAB > DTAB, because the longer alkyl chain of CTAB increased cell membrane permeability, causing cell lysis that allowed solvent-pigment contact. A CTAB dose of 25 mM and treatment for 5 h gave the highest pigment extraction, nearly 30 and 12 mg/g dried biomass for chlorophyll a and carotenoids, respectively. In contrast, lipid recovery was better with the shorter alkyl-chain length, DTAB > CTAB. DTAB disrupted the cells less, which allowed the solvent to access more lipids held in the cells. Thus, the selection of surfactant and dosing strategy depends on which products are targeted. With moderate cell disruption, a moderate dose of CTAB (10 mM) was effective for recovering pigments and lipids simultaneously.
       
  • Preliminary data on the dietary safety, tolerability and effects on lipid
           metabolism of the marine microalga Tisochrysis lutea
    • Abstract: Publication date: September 2018Source: Algal Research, Volume 34Author(s): Elisabetta Bigagli, Lorenzo Cinci, Alberto Niccolai, Natascia Biondi, Liliana Rodolfi, Massimo D'Ottavio, Mario D'Ambrosio, Maura Lodovici, Mario R. Tredici, Cristina LuceriAbstractThe marine microalga Tisochrysis lutea is an interesting source of nutrients and bioactive compounds such as fucoxanthin and docosahexaenoic acid, used so far mainly in aquaculture. To investigate its dietary safety and tolerability on mammals, male Sprague-Dowley rats were fed an AIN-76 diet containing 20% of T. lutea F&M-M36 biomass, for 1 month.T. lutea rich diet showed an apparent digestibility similar to that of the non enriched AIN-76 diet and did not affect growth or animal behavior, but was associated to higher water intake, urinary excretion and urinary sodium probably due to the high salt content of the algal biomass. However, blood pressure, creatinine and urea, kidney morphology and heart left ventricular wall thickness were not affected. T. lutea fed rats showed an increase in cholesterol high density lipoprotein, HDL (p 
       
  • The combined influence of 24‑epibrassinolide and 3‑indoleacetic acid
           on growth and accumulation of pigments and fatty acids in the microalgae
           Scenedesmus quadricauda (CPCC-158)
    • Abstract: Publication date: November 2018Source: Algal Research, Volume 35Author(s): Tatiana A. Kozlova, Bruce P. Hardy, David B. LevinAbstractInterest in the use of wastewaters of different origins for the industrial production of microalgal biomass for biofuels and bioproducts has stimulated studies on the influence of a variety of compounds in wastewaters on algal physiology. Following the previously published work on the impact of four single phytohormones on the physiology of the microalga Scenedesmus quadricauda (CPCC-158), we investigated the combined effect of the 24‑epibrassinolide (EBL) and 3‑indoleacetic acid (IAA) on S. quadricauda biosynthesis and biomass production. Synergistic increases in S. quadricauda biomass production, chlorophyll-a accumulation, total carotenoid accumulation, as well as total and major neutral lipid (triacylglyceride) accumulation were observed for most of the mixed hormone trials. Mixed hormones had stimulatory effects on growth and biosynthesis of S. quadricauda, but the influence of mixed hormones on algae growth (maximum 1.6-times greater) was less than their influence on algal biosynthesis (maximum 1.7-, 2.7-, and 3.3-fold for chlorophyll-a, total carotenoids, and fatty acids, respectively) compared with single hormone treatments. The mechanism of EBL and IAA cross-talk is likely specific to targeted biosynthetic pathways. The type of relationship between two mixed phytohormones was assessed with Ting-Chao Chou Test. Our results highlight the need for further research on the combined influence of phytohormones on algae physiology.
       
  • Recovery of lipophilic products from wild cyanobacteria (Aphanizomenon
           flos-aquae) isolated from the Curonian Lagoon by means of supercritical
           carbon dioxide extraction
    • Abstract: Publication date: November 2018Source: Algal Research, Volume 35Author(s): Michail Syrpas, Jolita Bukauskaitė, Ričardas Paškauskas, Loreta Bašinskienė, Petras Rimantas VenskutonisCyanobacteria are widely distributed photosynthetic microorganisms that can be found in almost every terrestrial and aquatic environment. In heavily eutrophicated water bodies, massive proliferation of cyanobacteria can lead into excessive surface water blooms. Over the last decades the presence of Aphanizomenon sp. dominated blooms have also been reported in the Curonian Lagoon. Recent reports indicate that removal of wild cyanobacterial blooms from the Curonian Lagoon as a management measure should be prioritized. In this study, the utilization of wild cyanobacteria as a potential source of high-added value products by means of supercritical CO2 extraction (SFE-CO2) is reported. Central composite design (CCD) and response surface methodology (RSM) were employed to optimize SFE-CO2 parameters (temperature, pressure and time) to obtain high yield lipophilic extracts. Under optimal conditions (42.5 MPa, 55 °C and 120 min), SFE-CO2 yielded 4.43 g/100 g DW of non-polar extract, showing 20% higher extraction efficiency at 3-fold lower extraction time as compared to the conventional Soxhlet extraction. SFE-CO2 fraction was rich in α‑linolenic acid (27% of total fatty acids) and α‑tocopherol (293 μg/g extract). Moreover, the total phenolic content and the in vitro radical scavenging capacity of extracts and solid fractions were evaluated too. Furthermore, preliminary life cycle assessment (LCA) showed that SFE-CO2 had a higher life cycle impact as compared to the hexane system. Thus, SFE-CO2 could be utilized to valorise wild cyanobacteria into valuable products with various industrial applications.Graphical abstractUnlabelled Image
       
  • Influence of Fe/HZSM-5 catalyst on elemental distribution and product
           properties during hydrothermal liquefaction of Nannochloropsis sp.
    • Abstract: Publication date: November 2018Source: Algal Research, Volume 35Author(s): Ziyun Liu, Hao Li, Jianli Zeng, Minsheng Liu, Yuanhui Zhang, Zhidan LiuHydrothermal liquefaction (HTL) is a promising thermochemical technology to produce biocrude oil from algae; however, further improvement of the process efficiency is still required. In this study, we used a cost-effective catalyst (Fe/HZSM-5) during HTL of microalgae Nannochloropsis sp. The highest biocrude oil yield (38.1 ± 3.2%) was achieved at 365 °C with the inclusion of Fe/HZSM-5, which improved the biocrude oil yield by 25% compared with the non-catalyzed group. In addition, Fe/HZSM-5 showed a positive effect on influencing element migration during the HTL process. An increase of carbon in the biocrude oil and increase of nitrogen in the aqueous phase were observed, which would benefit downstream processing, including biocrude oil upgrading and nutrients recovery. Furthermore, the presence of low-molecular weight ketones, acids, amides and phenols in the biocrude oil indicated improvement of the oil quality. Hence, Fe/HZSM-5 could be a promising catalyst for the HTL of algae, enhancing biocrude oil production and regulating the distribution of carbon and nitrogen in the product fractions.Graphical abstractUnlabelled Image
       
  • Combinations of Ulva and periphyton as biofilters for both ammonia and
           nitrate in mariculture fishpond effluents
    • Abstract: Publication date: September 2018Source: Algal Research, Volume 34Author(s): Lior Guttman, Suzanne E. Boxman, Roy Barkan, Amir Neori, Muki ShpigelAbstractPeriphyton-based biofilters for aquaculture effluent possess multiple advantages, in water oxygenation, CO2 reduction and production of useful biomass. The performance of a marine periphyton biofilter, in terms of uptake rate and efficiency in removing different forms of nitrogen, was investigated. A periphyton biofilter was paired with an upstream macroalgae biofilter stocked with Ulva to expose the periphyton to ammonia-depleted but nitrate-rich effluent. Three trials compared the removal of total ammonia-N (TAN), nitrate (NO3-N), total N and phosphorus. The biofiltration and growth performance of (1) the periphyton downstream to the Ulva tank, (2) periphyton alone and (3) Ulva alone were compared. Biofiltration performance was evaluated at different areal loads of TAN and NO3-N.Periphyton growth performance did not depend on the effluent nutrient composition or on N loads, and yielded between 7.3 and 10.6 g dry weight m−2 d−1. While the Ulva preferred uptake of TAN over NO3-N, the periphyton showed no preference between them, demonstrating flexible shifts between TAN and NO3-N uptake. TAN uptake rate by the periphyton was not influenced by the effluent composition. However, periphyton NO3-N uptake rate and efficiency rose about fivefold, up to 1.4 g NO3-N m−2 d−1 and 63%, respectively, upon depletion of TAN areal load below 0.18 g N m−2 d−1 (
       
  • Marine invasive macroalgae: Turning a real threat into a major opportunity
           - the biotechnological potential of Sargassum muticum and Asparagopsis
           armata
    • Abstract: Publication date: September 2018Source: Algal Research, Volume 34Author(s): Susete Pinteus, Marco F.L. Lemos, Celso Alves, Agnieszka Neugebauer, Joana Silva, Olivier P. Thomas, Luis M. Botana, Helena Gaspar, Rui PedrosaAbstractMarine invasive species are widely recognized as one of the worst threats to marine ecosystems integrity, unbalancing native communities, which may lead to paramount ecological and economic impacts. Within invasive seaweeds, Sargassum muticum and Asparagopsis armata are recognized as successful invaders in Europe and America. Despite several attempts to control the spread of marine invaders, until now, all have proven to be elusive, and therefore, alternative strategies should be embraced.Worldwide, seaweeds have been increasingly explored due to their ability to produce bioactive compounds. However, one of the main problems associated with the production/extraction of these bioactive compounds for new products development, is the source availability and the potential negative environmental consequences of this exploitation.Within this framework, the use of invasive species to obtain natural bioactive compounds presents us with a two-folded opportunity - high availability of the biological material for the extraction of unique bioactive compounds for new products development, and through specimen collection, mitigating negative effects caused by alien species, contributing for ecosystem integrity and sustainability.Over the last decades, the brown seaweed S. muticum and the red A. armata have been studied all over the world for their capacity to produce bioactive compounds, with main results pointing towards their high potential as producers of antioxidant, antifouling, antimicrobial, and antitumor compounds.The present review summarizes the biotechnological potential of S. muticum and A. armata as producers of bioactive compounds, while addressing the potential use of global threats as important blue growth pawns.
       
  • Hot and bright: Thermal and light environments for the culture of
           Oedogonium intermedium and the geographical limits for large-scale
           cultivation in Australia
    • Abstract: Publication date: September 2018Source: Algal Research, Volume 34Author(s): Andrew Cole, Christina Praeger, Thomas Mannering, Rocky de Nys, Marie MagnussonAbstractThe successful implementation of the intensive cultivation of freshwater macroalgae for bioremediation purposes relies on the consistent year-round uptake of nutrients, which is closely linked to the amount of biomass produced. This study examined how light and temperature influence the biomass productivity and photosynthetic efficiency of a tropical strain of the freshwater macroalga Oedogonium intermedium (Wittrock ex Hirn). We subsequently use this information to identify, at a coarse level, the locations within Australia that can provide a thermal and light environment that is conducive to the intensive year-round, production of this species. The optimal temperature range to cultivate O. intermedium is between 20 and 35 °C, and in general productivity increased with increasing photon flux within this temperature range. At temperatures outside of this optimal range O. intermedium still had positive growth when cultured at a constant temperature of as low as 15 °C and as high as 40 °C, but productivity was impaired, and these temperatures represent the minimum and maximum temperature thresholds for chronic exposure. At low temperatures, higher photon flux rates increased productivity, however, at higher temperatures (>35 °C) a higher photon flux decreased productivity. These experimental insights have enabled us to identify, at a coarse level, locations within Australia that provide a suitable thermal and light environment for the year-round cultivation of O. intermedium. In general, latitudes of ≤25° provide a thermal and light environment that can maintain a high rate of biomass productivity year-round. In contrast, most locations at latitudes higher than 25° provide a suitable environment only during the summer months. During winter the combination of low temperatures and low solar irradiances will prevent the successful cultivation of this tropical strain. In these cooler locations alternative species of locally adapted, freshwater macroalgae should be identified and domesticated to ensure bioremediation outcomes are maintained at these lower latitudes.
       
  • Effects of two toxic cyanobacterial crude extracts containing
           microcystin-LR and cylindrospermopsin on the growth and photosynthetic
           capacity of the microalga Parachlorella kessleri
    • Abstract: Publication date: September 2018Source: Algal Research, Volume 34Author(s): Ana L. Pereira, Catarina Santos, Joana Azevedo, Teresa P. Martins, Raquel Castelo-Branco, Vitor Ramos, Vitor Vasconcelos, Alexandre CamposAbstractSecondary metabolites produced by cyanobacteria like microcystins (MC) and cylindrospermopsin (CYN) have been frequently studied because of their toxicity in humans and other animals. However, the function(s) of these metabolites remain largely unknown. The objective of this work was to deepen the knowledge in this research area and characterize the allelopathic effects of the cyanotoxins MC and CYN on the green alga Parachlorella kessleri. Several assays were carried out under controlled laboratory conditions with cyanobacterial cell extracts from Microcystis aeruginosa and Chrysosporum ovalisporum, producers of MC-LR and CYN respectively, at concentrations of 55 and 150 μg/L. The effects of CYN at 150 μg/L was also studied in P. kessleri growing in Z8 medium with altered nutrient composition. The data obtained indicate that growth rate and photosynthetic pigments were not affected by the exposure to cyanobacterial toxic extracts compared to control. However, the growth rate and photosynthetic pigments content changed during the 14 days of P. kessleri cultivation, in both groups (control and treatment), which may reflect the culture conditions and P. kessleri growth curve. It was also possible to verify that nutrients' concentration of the microalga culture medium does not influence the growth rate of the green microalga or the biological activity of the cyanobacterial extracts. In conclusion, under these specific laboratory conditions, there were no toxic or allelopathic effects of M. aeruginosa and C. ovalisporum crude extracts, which demonstrates the high tolerance of this phytoplanktonic species for the cyanobacterial toxins MC and CYN and other metabolites.
       
  • Understanding the nitrogen uptake and assimilation of the Chinese strain
           of Aureococcus anophagefferens (Pelagophyceae)
    • Abstract: Publication date: September 2018Source: Algal Research, Volume 34Author(s): Linjian Ou, Yangyang Cai, Wenyu Jin, Zhou Wang, Songhui LuAbstractBrown tides caused by Aureococcus anophagefferens have occurred annually and severely impacted on the local ecology and economy in the coastal waters of Qinhuangdao, China since 2009. The uptake preference, pigment composition and growth responses of the Chinese strain of A. anophagefferens to different nitrogen substrates were studied in the laboratory to better understand its nitrogen (N) strategies and compare the findings with those from the other strains in the U.S.A. Our results indicated that A. anophagefferens had a high absolute uptake rate (ρmax) for NH4+ and low half-saturation constants (Ks) for NO3− and urea. It grew faster on the organic substrates (urea and glutamic acid) than that on the inorganic substrates (NO3− and NH4+). A. anophagefferens had higher contents of cellular pigments for both photosynthesis (chlorophyll a, chlorophyll c2, 19′-butanoyloxyfucoxanthin and fucoxanthin) and photoprotection (β-Carotene and diadinoxanthin) on urea than did on NO3− and NH4+, suggesting a stronger capability for photosynthesis on urea. A. anophagefferens had higher contents of cellular carbon, N and proteins on urea than did on NO3− and NH4+, suggesting a stronger capability for the acclimation and storage of C and N on urea. A. anophagefferens produced more β-carotene rather than chlorophyll a on glutamic acid and thus inhibited photosynthesis and carbon fixation. We found in this study that urea was the best N substrate for the growth of A. anophagefferens. A. anophagefferens might have a competitive advantage over other phytoplankton in waters enriched with DON, particularly with urea.
       
  • Hydroxyl radical pretreatment for low-viscosity sodium alginate production
           from brown seaweed
    • Abstract: Publication date: September 2018Source: Algal Research, Volume 34Author(s): Feng Gao, Xiumin Liu, Wuxi Chen, Wei Guo, Limei Chen, Demao LiAbstractFormalin pollution and water wastage are two of the main problems in the alginate industry. A novel pre-extraction treatment method based on the Fenton and electro-Fenton reactions is proposed to disrupt the cell wall of Macrocystis pyrifera and reduce the alginate filtrate viscosity, as an environmentally friendly process for alginate extraction. Under optimum Fenton (7.4 mM FeSO4 90 min) and electro-Fenton (EF-Fere 9 V, 90 min at pH 3, stirring) pre-extraction treatment conditions, the filtrate viscosity decreased by 83.99% and 97.79%, respectively. The filtrate viscosity decreased significantly as compared to the traditional approach under suitable operating conditions. Using of electro-Fenton for pre-extraction reduced water consumption by 60% in the filtration step and eliminated the use of formaldehyde during the process, reducing production costs and environmental pollution. Moreover, the yield and the quality of the alginate extracted after the pre-extraction improved.
       
  • Milking exopolysaccharides from Botryococcus braunii CCALA778 by
           membrane filtration
    • Abstract: Publication date: September 2018Source: Algal Research, Volume 34Author(s): Rafael García-Cubero, Weiliang Wang, Judit Martín, Elisabeth Bermejo, Lolke Sijtsma, Arnoud Togtema, María J. Barbosa, Dorinde M.M. KleinegrisAbstractThe aim of this work was to optimize the efficiency of extraction and recovery, also known as ‘milking’, of exopolysaccharides (excreted polysaccharides, EPS) from continuous cultures of Botryococcus braunii CCALA778. First, an indoor process was developed and optimised, ensuring the highest milking efficiency without compromising culture viability. For this, photobioreactors were operated in a photo-chemostat mode under simulated outdoor conditions of a typical summer at AlgaePARC (51°59′44.1”N 5°39′26.2″E) in Wageningen, The Netherlands. Once a steady state was reached, areal productivities of 23 g m−2 d−1 and 3 g m−2 d−1 for biomass and EPS were achieved. EPS milking was done by membrane filtration of one reactor volume at the beginning of the dark period. After optimization, the maximum recovery of EPS, without damaging the cells, was 12%; yielding a daily EPS extraction rate of 0.36 g m−2 d−1. The optimised process was scaled-up and applied outdoors during the summer (at AlgaePARC facilities). Outdoor cultures showed 25% lower biomass productivity (17 g m−2 d−1) but an 25% higher EPS productivity (4 g m−2 d−1). The efficiency in the milking, however, decreased as compared to indoor results. Only 3% of the total content of EPS produced outdoors was milked (0.12 g m−2 d−1). To improve the EPS milking process, future research should focus on increasing the EPS extraction yield without negatively influencing its production by Botryococcus braunii.
       
  • Simultaneous production of antioxidants and starch from the microalga
           Chlorella sorokiniana
    • Abstract: Publication date: September 2018Source: Algal Research, Volume 34Author(s): Ganna Petruk, Imma Gifuni, Anna Illiano, Mariana Roxo, Gabriella Pinto, Angela Amoresano, Antonio Marzocchella, Renata Piccoli, Michael Wink, Giuseppe Olivieri, Daria Maria MontiAbstractIn recent years, microalgae have gained considerable importance as potential source of biofuels and bioplastics. However, these markets are still developing, as the high costs of cultivation ask for exploiting microalgae into new areas and with a biorefinery approach towards a multicomponent cascade extraction process. Here, a sequential processing strategy was used to extract starch with high yield from Chlorella sorokiniana under biocompatible conditions. The extract residue was then tested as a potential source of antioxidants. We found a strong protective activity of the extract residue towards oxidative stress in vitro on human colon cancer cells and in vivo on Caenorhabditis elegans nematodes, by inhibiting ROS production and activating DAF-16/FOXO transcription factor pathway. A pool of molecules from three different classes (fatty acids, photosynthetic pigments and carotenoids) was identified as responsible for the antioxidant activity. To our knowledge, this is the first report on the obtainment, from a “waste” fraction, of high value products endowed with antioxidant activity tested in cell-based models and in vivo.
       
  • Life cycle assessment of industrial scale production of spirulina
           tablets
    • Abstract: Publication date: September 2018Source: Algal Research, Volume 34Author(s): Chensong Ye, Dongyan Mu, Naomi Horowitz, Zhonglin Xue, Jie Chen, Mingxiong Xue, Yu Zhou, Megan Klutts, Wenguang ZhouSpirulina platensis has been successfully commercialized as functional food ingredients, animal feed and medicine due to its high contents of protein, beta-carotene, vitamins, and minerals. In this study, we investigated the environmental performance (cradle-to-gate) of edible Spirulina tablets using Life Cycle Assessment (LCA). A comparative analysis with other three traditional foods or diets was conducted by using various nutrient values as functional units (e.g., protein content and a composite nutrient score) in the analysis. This research showed that Spirulina tablets production for protein caused environmental impacts mainly in fossil fuel use, acidification, climate change, smog formation, and eutrophication. The impact of the cultivation stage was the highest environmental impacts among all production stages resulting from the extensive use of chemicals, nutrients, and energy. The impacts of algae food production are around 2–5 times to algae production for biofuels which was also modeled in this study. In terms of protein production, algae tablet cause higher impacts than traditional terrestrial crops but lower impacts than protein from animal products. However, as the algae contain a wide variety of nutrients, especially high micronutrients such as the beta-carotene, the environmental impacts of producing the same nutrient combinations of protein and beta-carotene from carrot + tofu were higher than producing Spirulina tablets. The results in this work can be used to assess edible algae production inventories and provide reliable information for development of more sustainable products and processes.Graphical abstractUnlabelled Image
       
  • Pilot-scale demonstration of efficient ammonia removal from a
           high-strength municipal wastewater treatment sidestream by algal-bacterial
           biofilms affixed to rotating contactors
    • Abstract: Publication date: September 2018Source: Algal Research, Volume 34Author(s): Daniel B. Johnson, Lance C. Schideman, Thomas Canam, Robert J.M. HudsonAbstractThis report details our investigation of a novel, fixed-biofilm algal and bacterial system for the treatment of high-strength municipal anaerobic digester filtrate. Each reactor in the pilot-scale system comprises multiple Algaewheel™ rotating algal contactors (RACs) that help efficiently oxygenate the anaerobic digester filtrate being treated in a shallow tank. Total ammonia nitrogen (TAN) removal by microbial oxidation and anabolic uptake varied between 45 and 60% at hydraulic retention times (HRTs) of 0.5–2 days. Of the TAN removed during treatment,>95% was oxidized to nitrite with 27–36% subsequently evolved as N2 and only 3–11% oxidized to nitrate. The low extent of nitrate formation makes biological nutrient removal less costly, since nitrite reduction demands less oxygen, by 25%, and organic carbon, by 40%, than nitrate reduction. In addition, due to the efficient aeration by RACs, it should be possible to design systems for sidestream treatment of digester filtrate that require up to 80% less electricity than are typical for aerobic ammonia oxidation.
       
  • Isolation of high-CO2-acclimated Micractinium sp. strains from eutrophic
           reservoir water
    • Abstract: Publication date: September 2018Source: Algal Research, Volume 34Author(s): Sakie China, Katsuhiko FujiiAbstractCO2-tolerant microalgae have received much attention for their potential application in the fixation of CO2 from industrial flue gas. Consequently, there have been extensive efforts to isolate and characterize these microalgae. However, microalgae acclimated to high levels of CO2, which optimally grow at CO2 concentrations close to that of industrial flue gas, can be more useful for CO2 fixation. Several microalgal strains have been reported to be tolerant to high levels of CO2, but the optimal CO2 concentrations for their growth is generally lower than their maximum tolerable CO2 level. In the present study, we isolated several microalgal strains from freshwater reservoirs. Among the isolates, two Micractinium sp. strains were found to grow preferably at high levels of CO2. The strains grew best at around 30% CO2, and were capable of growing even at 80% CO2. As a combustion gas from coal-fired power plants, the largest CO2 source, contains around 15% of CO2, it can be a suitable carbon source for the strains in photoautotrophic cultivation. Interestingly, the strains were found to contain high amounts of vitamin B6 and γ-aminobutyric acid. Among the identified fatty acids, the C18 unsaturated and C16 saturated fatty acids were the most dominant. Based on these results, the strains appear to be promising candidates for application in nutraceutical production using CO2 in industrial flue gas as a substrate.
       
  • Energy minimization of a tilted panel filtration system for microalgae
           filtration: Performance modeling and optimization
    • Abstract: Publication date: September 2018Source: Algal Research, Volume 34Author(s): A. Eliseus, Z.A. Putra, M.R. Bilad, N.A.H.M. Nordin, M.D.H. Wirzal, J. Jaafar, Asim L. Khan, AqshaAbstractTo realise the enormous potential of biofuel feedstock for commercial purposes, the energy for harvesting microalgae biomass must be significantly lowered. A recently developed tilted panel filtration system offers ease of unit operation and energy saving, but it still can be further optimized to lower its energy consumption. This paper investigates and optimizes the concurrent effects of tilting angle (θ), specific aeration demand (SADm) and switching frequency (Sf) in a tilted panel system on microalgae filtration permeability using developed empirical equations. Experiment was designed to create random sets of operational parameters, and the experimental data were plotted with response surface methodology to develop permeability model. Analysis of variance verifies that the model is excellent fit with high correlational value (p-value 
       
  • New ultra-flat photobioreactor for intensive microalgal production: The
           effect of light irradiance
    • Abstract: Publication date: September 2018Source: Algal Research, Volume 34Author(s): Imma Gifuni, Antonino Pollio, Antonio Marzocchella, Giuseppe OlivieriAbstractOne of the main bottlenecks for the exploitation of microalgae is the low biomass concentration of the cultures: high harvesting costs and large cultivation area are always required. This bottleneck is partly due to a low light availability along the optical path of photobioreactors. An ultra-thin flat photobioreactor (UFP) (3 mm thickness) was proposed to increase both biomass concentration and productivity. The performance of the UFP was investigated: the effects of incident light intensity - from 50 and 1000 μmolPhotons m−2 s−1 - on cell growth, photosynthesis rate, and biochemical composition of Chlorella sorokiniana were characterized. The maximum microalgal concentration and the maximum areal productivity were 24 kg m−3 and 1.34 g m−2 h−1, respectively. The cell specific growth rate reached 0.1 h−1 at 1000 μmol m−2 s−1. The biochemical composition of the microalgal biomass changed with the light irradiance. Protein content increased from 35 up to 53% of DW with increasing the light intensity. The concentration of storage compounds, such as starch and lipids, decreased from 30 to 16% and from 30 to 10%, respectively, with increasing the light intensity. A limit in the maximum biomass concentration achievable was identified. Several hypotheses have been discussed. A light transfer model was applied to assess the presence of light limitation. Other hypotheses were analyzed in depth and the most feasible explanations were found to be a) the damage to the photosystem when exposed for long period to continuous and high light irradiances, b) nutrient limitation due to salt precipitation or c) gas-liquid transfer of the CO2. Finally, benefits and drawbacks of the ultra-thin culture system were discussed.
       
  • Pilot-scale production of poly-β-hydroxybutyrate with the cyanobacterium
           Synechocytis sp. CCALA192 in a non-sterile tubular photobioreactor
    • Abstract: Publication date: September 2018Source: Algal Research, Volume 34Author(s): Clemens Troschl, Katharina Meixner, Ines Fritz, Klaus Leitner, Alejandra Palacios Romero, Adriana Kovalcik, Petr Sedlacek, Bernhard DrosgAbstractThe biopolymer poly-β-hydroxybutyrate (PHB) can be used as a promising bioplastic. It has a broad range of applications and is degraded relatively rapidly by soil organisms. Like many prokaryotes, the cyanobacterium Synechocystis sp. CCALA192 produces this biopolymer as a storage compound, especially under nutrient limitation.In a 200-L tubular photobioreactor, we cultivated Synechocystis sp. CCALA192 semi-continuously over a period of 75 days with CO2 as sole carbon source. A two-stage cultivation strategy was performed, where after 5–7 days nitrogen was depleted and the culture started to produce PHB and gradually turned from blue-green to yellow. After 16–20 days, 90% of the culture were harvested and the residual 10% were used as inoculum for the following cycle. The harvested culture had an average biomass concentration of 1.0 g/L with an average PHB content of 12.5% of cell dry weight. After restarting with fresh nutrients, the yellow culture turned blue-green again and degraded the PHB within 24–48 h. When nitrogen of the medium was consumed, PHB was produced again and the cycle continued. In the late stage of each production cycle, a ripening process was observed, where no CO2 was consumed but the PHB concentration was still rising at the expense of the existing glycogen rich biomass.Establishing a stable Synechocystis sp. CCALA192 culture under non-sterile conditions turned out to be difficult, as this small unicellular organism is very sensitive and easily grazed by protozoa. Therefore, a special cultivation strategy with partially anoxic conditions was necessary.
       
  • Carbon, nitrogen, and phosphorus removal, and lipid production by three
           saline microalgae grown in synthetic wastewater irradiated with different
           photon fluxes
    • Abstract: Publication date: September 2018Source: Algal Research, Volume 34Author(s): Manuel Sacristán de Alva, Víctor Manuel Luna Pabello, María Teresa Orta Ledesma, Modesto Javier Cruz GómezMariculture production has increased in the last decades, with untreated wastewater discharged directly into the sea, impacting coastal ecosystems. There is a need for mariculture wastewater treatment systems that are cost-effective. This can be met by the implementation of wastewater treatment systems that in addition to removing pollutants are capable of producing valuable by-products such as biomass for the biofuel industry. In this study, Dunaliella sp., Nannochloropsis sp. and Tetraselmis sp. microalgae were cultivated in controlled environments simulating mariculture wastewaters. Single stage culture systems were used to grow these microalgae, the growing conditions included inducing stress with different photon flux densities (900, 1500 and 2000 μmol m−2 s−1), and low carbon, nitrogen and phosphorus concentrations obtained at the stationary phase, in order to force these microalgae to increase their lipid content. The best results were obtained with Tetraselmis sp., which achieved 132.8 mg L−1 day−1 of biomass productivity at 900 μmol m−2 s−1. Nevertheless the best lipid productivity was reached at 1500 μmol m−2 s−1, also by Tetraselmis sp., being 29.5 mg L−1 day−1, where biomass productivity was of 124.5 mg L−1 day−1. All three microalgae species were able to remove>90% of nitrogen and orthophosphates, and 80% of carbon, which makes them suitable for treating mariculture wastewater, and in addition, represent a valuable high lipid content biomass byproduct usable as raw material for biodiesel synthesis.Graphical abstractUnlabelled Image
       
  • Response of Gracilaria lemaneiformis to nitrogen deprivation
    • Abstract: Publication date: September 2018Source: Algal Research, Volume 34Author(s): Yang Wang, Yinqi Feng, Xiaojuan Liu, Mingqi Zhong, Weizhou Chen, Fan Wang, Hong DuAbstractThe rhodophyte Gracilaria lemaneiformis plays a significant role in nitrogen (N) utilization as an economic macroalgae. However, very little is known about how G. lemaneiformis adapts to N deprivation. In this study, G. lemaneiformis were pre-cultured in artificial seawater with 50 μM inorganic N for 4 days and two groups were set after the pre-culture, N-deprived treatment with 0 μM N nutrient and N-replete control with 50 μM N nutrient. The response of G. lemaneiformis to N deprivation was analyzed at physiological, transcriptomic and proteomic levels. Physiologically, our data revealed that N depletion resulted in the increase of C/N ratio in a sustained period of N deprivation. Nitrogenous compounds were available in N depletion, including amino acids, phycoerythrin and soluble protein, but not DNA and chlorophyll-a. Furthermore, transcriptomic analysis underscored two major responses of G. lemaneiformis to N deprivation: 1) N assimilation pathway, PSII and PSI initially responded to N deprivation in 4 days, but declined sharply during the N deprivation; 2) Carbon fixation and glycolysis metabolism both rapidly recovered during a sustained period of N deprivation from strong repression of the first 2 days. Proteomics data indicated that electron-transfer proteins in the photosynthesis of G. lemaneiformis increased dramatically, but phycoerythrin protein decreased under N deprivation. However, GS protein and ribulose-bisphosphate carboxylase (RubisCO) protein remained stable. Therefore, this investigation revealed that the C-N metabolism was essential to survival under N deprivation.
       
  • High-density cultivation of microalgae continuously fed with unfiltered
           water from a recirculating aquaculture system
    • Abstract: Publication date: September 2018Source: Algal Research, Volume 34Author(s): Sophia Egloff, Fridolin Tschudi, Zala Schmautz, Dominik RefardtAbstractWater from recirculating aquaculture systems (RAS) has been shown to be a suitable growth medium for microalgae and their cultivation can, therefore, be used to reduce RAS emissions. However, while efficient wastewater treatment is possible, the nutrient content of RAS water limits attainable microalgae biomass densities to 1–2 g l−1 at best, which requires frequent harvesting of microalgae. We have taken advantage of the constant evaporation of water from an open thin-layer photobioreactor (200 l volume, 18 m2 illuminated surface, artificial supply of CO2) to continuously add water from RAS to a microalgae culture and thereby provide nutrients for continued growth while evaporating all water. To test for a possible inhibitory effect of RAS water on microalgae growth, components of mineral medium were omitted stepwise in subsequent cultivations and replaced by RAS water as the only source of nutrients. This approach showed that microalgae can be grown successfully for up to three weeks in RAS water without additional nutrients and that high (20 g l−1) biomass densities can be attained. While growth in wastewater did not reach productivities measured in mineral medium, analysis of growth data suggested that this reduction was not due to an inhibitory effect of the RAS water but due to an insufficient supply rate of nutrients, even though RAS water contained up to 158 mg l−1 NO3-N. It is, therefore, concluded that this method can be used to fully treat the wastewater discharge of a RAS. Furthermore, because both water evaporation from and microalgae growth in the photobioreactor correlated positively with each other due to their shared dependency on solar radiation, supply of nutrients continuously adjusts to changes in demand. It is estimated that the area of a photobioreactor required to treat all emissions of a RAS requires approximately 6.5 times the area of the latter.
       
  • Characterization of plant carbon substrate utilization by
           Auxenochlorella protothecoides
    • Abstract: Publication date: September 2018Source: Algal Research, Volume 34Author(s): Brian W. Vogler, Shawn R. Starkenburg, Nilusha Sudasinghe, Jenna Y. Schambach, Joseph A. Rollin, Sivakumar Pattathil, Amanda N. BarryAlgae hold great potential as a source of renewable fuel due to their ability to produce refinery-compatible diesel and jet fuel precursors. Significant effort has been made to maximize productivity under photoautotrophic growth conditions; however, little progress has been made to discover and understand reduced carbon assimilation pathways or enzymatic degradation of complex carbon substrates in algae. We purport that utilization of plant-based carbon substrates in addition to photosynthesis (mixotrophic growth) for biochemical assimilation into biomass, biofuels, and bioproducts, can increase cultivation productivity and improve the economic viability of algal-derived biofuels. Herein we report that a freshwater production strain of microalgae, Auxenochlorella protothecoides UTEX 25, is capable of directly degrading and utilizing non-food plant substrates, such as switchgrass, for cell growth. Glycome profiling of plant substrates before and after addition to A. protothecoides cultures demonstrates the utilization of xyloglucans. Genomic, proteomic and transcriptomic analyses revealed the identity of many enzymes that are hypothesized to be involved in complex carbohydrate degradation, including several family 5 and 9 glycosyl hydrolases. This work paves the way for future designer engineering of plant‑carbon utilization to further improve productivity of algal production strains.Graphical abstractUnlabelled Image
       
  • Supercritical carbon dioxide extraction and fractionation of lipids from
           freeze-dried microalgae Nannochloropsis oculata and Chlorella vulgaris
    • Abstract: Publication date: September 2018Source: Algal Research, Volume 34Author(s): Sara Obeid, Nicholas Beaufils, Séverine Camy, Hosni Takache, Ali Ismail, Pierre-Yves PontalierAbstractThis study deals with the selective extraction of neutral lipids from microalgae. We investigated the consequences of bypassing cell-wall disintegration before supercritical carbon dioxide extraction. Different operating parameters (use of co-solvent, pressure, and time) were tested on freeze-dried Chlorella vulgaris and Nannochloropsis oculata. The solid phase extraction technique (SPE) was used throughout the extraction process to assess variations in the yield of liberated neutral lipids, glycolipids, and phospholipids. Under operating conditions, 97% of neutral lipids were extracted from C. vulgaris using ethanol (10% v/v) as co-solvent. Neutral lipids from N. oculata represented most of the extracts (83%), whereas the proportion of glycolipids and phospholipids did not exceed 12.1% and 5.3%, respectively. Microscopic observation showed that cell wall integrity was maintained during the extraction process.
       
  • Enhanced docosahexaenoic acid production by Crypthecodinium cohnii under
           combined stress in two-stage cultivation with date syrup based medium
    • Abstract: Publication date: September 2018Source: Algal Research, Volume 34Author(s): Leila Aliasgharzade Rumiani, Hassan Jalili, Abdeltif AmraneAbstractIn this study, date syrup was used for the first time as an alternative carbon source for Crypthecodinium cohnii growth and docosahexaenoic acid (DHA) production by response surface methodology. Four medium variables including date syrup concentration, pH, yeast extract and sea salt concentrations were considered to optimize biomass production. Maximum biomass concentration, 6.6 g/L, was achieved in 17 g/L date syrup concentration, 2 g/L yeast extract, 20 g/L sea salt and pH 7. After this optimization, a two-step feed strategy in fed batch cultivation was done in the optimized date based medium to enhance DHA production. The first step was dedicated to biomass formation and the second step was designed for DHA production. In the second step, single and for the first time, the combined effects of growth temperature shift from 25 to 20 °C, and nitrogen starvation on DHA production were investigated. The results revealed that the most appropriate strategy was a fed batch cultivation combined with both nitrogen depletion and temperature growth shift after 6th days from inoculation, leading to an enhancement of DHA production to 5.65 g/L, which was approximately twice the amount obtained considering the fact that the control was 2.9 g/L. Results revealed that date syrup based medium with two-step fed batch cultivation under combined stress can be an effective strategy for the production of valuable microalgal metabolites in heterotrophic conditions.
       
  • Comparative analysis of in vitro antioxidant capacities of
           mycosporine-like amino acids (MAAs)
    • Abstract: Publication date: September 2018Source: Algal Research, Volume 34Author(s): Priscila Torres, Janaína Pires Santos, Fungyi Chow, Marcelo J. Pena Ferreira, Deborah Y.A.C. dos SantosAbstractThe most common Mycosporine-like Amino Acids (MAAs) in red algae (asterina-330, shinorine, palythine, palythinol, and porphyra-334) were evaluated regarding their in vitro antioxidant capacities, comparing them with synthetic (BHT and Trolox) and natural (ascorbic acid, gallic acid, p-cumaric acid, quercetin, and rutin) antioxidants. Folin-Ciocalteu, ABTS+, and FRAP assays have the same reaction mechanism of electron transfer and usually show a positive correlation. However, the antioxidant capacities for the MAAs were discrepant between these assays. While porphyra-334, shinorine, and palythine were as active as, or more active than synthetic phenolic antioxidants (Trolox and BHT) in Folin-Ciocalteu assay, the antioxidant potentials of MAAs were lower than those of the standard compounds in ABTS+ and FRAP assays. The pH-dependent antioxidant power was hypothesized as an explanation for this distinct behavior and was evaluated through ABTS+ assay. Alkaline pH allows antioxidant capacities similar to Trolox in ABTS+ assay, supporting our hypothesis. Comparing to standard compounds, MAAs showed low activity using ORAC assay and were pro-oxidant in β-carotene/linoleic acid assay. Therefore, imino-MAAs present relevant in vitro antioxidant capacity under specific pH conditions in assays based on electron transfer.
       
  • Chemical structure investigation of tropical Turbinaria turbinata seaweeds
           and its derived carbon sorbents applied for the removal of hexavalent
           chromium in water
    • Abstract: Publication date: September 2018Source: Algal Research, Volume 34Author(s): Christelle Yacou, Sandro Altenor, Betty Carene, Sarra GaspardAbstractBiomass such as algae, has a great potential to simultaneously deliver renewable energy, bio-products and also better water quality. A pathway towards the realization of these benefits is through the development of valuable materials preferably inexpensive. This work reports on the successful exploitation of Turbinaria turbinata, a brown alga widely available in many tropical areas; which was used as sorbent for the removal of hexavalent chromium from aqueous media. By characterizing the surface material, we showed that the dried alga exhibits several polyfunctional metal-binding sites, enabled to use it as a raw material. Further surface modification (pre-treatment with acid) and structural modification (preparation of both chemically and physically activated carbons) was also carried out to enhance material adsorption properties. Significant improvement of metal uptake (up to 40 fold higher) was obtained, depending of the testing conditions. Based on a close examination of the surface chemistry and pH profiles, a mechanism describing the adsorption mechanism of the different systems was proposed.
       
  • Extraction of R-Phycoerythrin from marine macro-algae, Gelidium pusillum,
           employing consortia of enzymes
    • Abstract: Publication date: September 2018Source: Algal Research, Volume 34Author(s): Rochak Mittal, K.S.M.S. RaghavaraoExtraction of phycobiliproteins (R-phycoerythrin, R-PE) from macroalgae is difficult due to the presence of complex matrix of polysaccharides (agar, cellulose etc.) present in the cell wall which offers major hindrance for cell disruption. The present study is focused on the identification of suitable process conditions for the extraction of R-phycoerythrin (R-PE) from marine macroalgae, Gelidium pusillum (Stackhouse) Le Jolis., by enzymatic hydrolysis of polysaccharide-complex present in the macroalgal cell wall. Identification of optimum process conditions like incubation duration (2,4,6 h), incubation temperature (25, 30, 35, 40 °C) and enzyme to biomass ratio (0,20,40,60, 80 U/g biomass, fw) was carried out for agarase, cellulase and xylanase. Different relative proportions of these enzymes in a mixture at different pH (5.8, 6.8, 7.8) values were employed at the most suitable set of conditions. When employed alone, cellulase resulted in a minimum improvement (6%), agarase (14%) and xylanase the maximum (16%) on R-PE yield. Presence of cellulase in consortia has resulted in maximum improvement in R-PE yield (26%) at 25 °C and pH 5.8. Consortia of enzymes were more effective in improving the yield of biomolecules over the individual enzymes due to efficient hydrolysis of complex cell wall structure of biomass of Gelidium pusillum macroalgae and can be employed for the extraction of biomolecules also from other macroalgae.Graphical abstractUnlabelled Image
       
  • Non-catalytic fast pyrolysis and catalytic fast pyrolysis of
           Nannochloropsis oculata using Co-Mo/γ-Al2O3 catalyst for valuable
           chemicals
    • Abstract: Publication date: September 2018Source: Algal Research, Volume 34Author(s): Ribhu Gautam, R. VinuMicroalgae is projected as a promising third generation biomass feedstock for the production of biofuel and fine chemical intermediates. This study is focused on the selective production of chemicals from Nannochloropsis oculata microalga via catalytic fast pyrolysis technique using Co-Mo/γ-Al2O3 catalyst. Non-catalytic and catalytic fast pyrolysis (CFP) experiments were conducted in an analytical micropyrolyzer coupled with gas chromatograph/mass spectrometer to study the effects of temperature, catalyst-to-algae ratio, and metal loading on support on pyrolysate composition. The catalyst, Co-Mo/γ-Al2O3, was prepared using wetness incipient impregnation method, and characterized for its structure and pore size distribution. Catalyst-to-algae mass ratios used to study the pyrolysate composition and quality were 1:3, 1:1 and 2:1. The major organic compounds from both non-catalytic fast pyrolysis and CFP of the microalga were long chain nitriles, long chain alkanes and alkenes, polyaromatic and monoaromatic hydrocarbons. The optimum fast pyrolysis temperature under non-catalytic conditions that promoted the selectivity of aliphatic and aromatic hydrocarbons was 500 °C. The incorporation of Co-Mo/γ-Al2O3 catalyst promoted the formation of specific organic compounds like 1‑isocyanobutane and dimethylketene to the tune of 35% selectivity. The formation pathways for these compounds are proposed to involve dehydration, isomerization, ketonization and CH addition reactions of the amide and carboxylic acid moieties generated from the protein and lipid fractions of the alga. Owing to the low oxygen content in the pyrolysates from CFP, the estimated calorific value of organics in the pyrolysates was higher (33–39 MJ kg−1) than that of the microalga (18 MJ kg−1).Graphical abstractUnlabelled Image
       
 
 
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