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  Subjects -> BIOLOGY (Total: 3193 journals)
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BIOTECHNOLOGY (244 journals)                  1 2 | Last

Showing 1 - 200 of 244 Journals sorted alphabetically
3 Biotech     Open Access   (Followers: 8)
Advanced Biomedical Research     Open Access  
Advances in Bioscience and Biotechnology     Open Access   (Followers: 17)
Advances in Genetic Engineering & Biotechnology     Hybrid Journal   (Followers: 9)
Advances in Regenerative Medicine     Open Access   (Followers: 3)
African Journal of Biotechnology     Open Access   (Followers: 6)
Algal Research     Partially Free   (Followers: 11)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 69)
American Journal of Bioinformatics Research     Open Access   (Followers: 7)
American Journal of Polymer Science     Open Access   (Followers: 33)
Amylase     Open Access  
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: 45)
Applied Biosafety     Hybrid Journal  
Applied Food Biotechnology     Open Access   (Followers: 3)
Applied Microbiology and Biotechnology     Hybrid Journal   (Followers: 67)
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: 3)
Bio-Algorithms and Med-Systems     Hybrid Journal   (Followers: 2)
Bio-Research     Full-text available via subscription   (Followers: 4)
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)
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: 8)
Biotechnology & Biotechnological Equipment     Open Access   (Followers: 4)
Biotechnology Advances     Hybrid Journal   (Followers: 34)
Biotechnology and Applied Biochemistry     Hybrid Journal   (Followers: 44)
Biotechnology and Bioengineering     Hybrid Journal   (Followers: 159)
Biotechnology and Bioprocess Engineering     Hybrid Journal   (Followers: 6)
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: 17)
Biotechnology Law Report     Hybrid Journal   (Followers: 4)
Biotechnology Letters     Hybrid Journal   (Followers: 34)
Biotechnology Progress     Hybrid Journal   (Followers: 41)
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: 17)
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: 55)
Current Pharmaceutical Biotechnology     Hybrid Journal   (Followers: 9)
Current Research in Bioinformatics     Open Access   (Followers: 13)
Current Trends in Biotechnology and Chemical Research     Open Access   (Followers: 3)
Current trends in Biotechnology and Pharmacy     Open Access   (Followers: 8)
DNA and RNA Nanotechnology     Open Access  
EBioMedicine     Open Access  
Electronic Journal of Biotechnology     Open Access  
Entomologia Generalis     Full-text available via subscription   (Followers: 1)
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  
Horticultural Biotechnology Research     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)
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: 18)
International Biomechanics     Open Access  
International Journal of Bioinformatics Research and Applications     Hybrid Journal   (Followers: 14)
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: 4)
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 BioScience and Biotechnology     Open Access  
Journal of Biosecurity Biosafety and Biodefense Law     Hybrid Journal   (Followers: 3)
Journal of Biotechnology     Hybrid Journal   (Followers: 63)
Journal of Biotechnology and Strategic Health Research     Open Access   (Followers: 1)
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 Ecobiotechnology     Open Access  
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: 18)
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: 13)
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: 13)
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: 10)
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)

        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  [3155 journals]
  • Biological control of ciliate contamination in Chlamydomonas culture using
           the predatory copepod Acanthocyclops robustus
    • Abstract: Publication date: January 2019Source: Algal Research, Volume 37Author(s): Nguyen Thi Kim Hue, Bert Deruyck, Ellen Decaestecker, Dries Vandamme, Koenraad Muylaert Ciliates are a common but less-explored group of contaminants in microalgal cultures that feed on microalgae and can cause severe losses in productivity of cultures. The aim of this study was to evaluate the potential of biological control to eradicate ciliates from microalgal cultures. In lab-scale experiments, we used the carnivorous cyclopoid copepod Acanthocyclops robustus as a biological control agent to eliminate the ciliate Sterkiella from cultures of the microalga Chlamydomonas. Our experiments showed that the copepod Acanthocyclops robustus can consume up to 400 ciliates individual−1 day−1. Addition of 0.07 copepods mL−1 to a culture that was contaminated with 10 ciliates mL−1 resulted in a complete elimination of ciliates from the culture within 1 day and restored the algal biomass production at the level of a non-contaminated culture. Addition of copepods to a fresh Chlamydomonas culture did not cause a reduction in the microalgal biomass concentration, indicating that this copepod does not feed on Chlamydomonas. These laboratory-scale experiments indicate that copepods have potential to be used as a biological control agent to address the problem of contamination of large-scale microalgal cultures by ciliates.
       
  • Life cycle assessment of novel technologies for algae harvesting and oil
           extraction in the renewable diesel pathway
    • Abstract: Publication date: January 2019Source: Algal Research, Volume 37Author(s): Rui Shi, Robert M. Handler, David R. Shonnard There are many challenges and technical barriers to implementation of a viable commercial process to produce algae-based biofuels. Biofuels made from algae must typically go through a complicated series of unit processes for algae cultivation, harvesting, dewatering, oil extraction, conversion, and other logistical steps. The National Alliance for Advanced Biofuels and Bioproducts (NAABB) was developed to produce new technologies to be implemented by the algal biofuel industry in an effort to improve the process economics and environmental benefits associated with algae fuels. This LCA study investigated the environmental impacts associated with four harvesting and two extraction technologies developed by NAABB researchers. Gate-to-gate LCA results show that all novel technologies appear to have the potential to provide at least modest decreases in greenhouse gas (GHG) emissions compared to current default algae process technologies. 14 scenarios of different combinations of harvesting and extraction unit operations were further evaluated in the context of the full life cycle for producing algae-based renewable diesel. Results indicate that selection of a particular technology for a unit operation can have consequences that affect other stages of the full biofuels life cycle, both upstream and downstream from the unit operation in question. Considering material and energy inputs, operation efficiency, impacts on on-site recycled energy, and co-products credits, acoustic harvesting followed by acoustic oil extraction give the best performance on the overall lifecycle, which reduce the GHG emissions by roughly 45% compared to the base case. LCA modeling also demonstrates that co-products produced at various points of the value chain, for use within or outside the algae biofuels system boundary, considerably affect the LCA results beyond harvesting and extraction unit processes.
       
  • Direct estimation of microalgal flocs fractal dimension through laser
           reflectance and machine learning
    • Abstract: Publication date: January 2019Source: Algal Research, Volume 37Author(s): Patricio Lopez-Exposito, Carlos Negro, Angeles Blanco The pre-concentration of microalgal cultures through flocculation can be applied to reduce the harvesting costs of biomass. The microalgal flocs induced through flocculation must have the optimal size and geometry to enhance the performance of subsequent concentration operations. In this work, we propose a new method to estimate the average fractal dimension of Chlorella sorokiniana flocs based on correlating the suspension chord length distribution with the flocs average geometry through a machine learning random forest regression model. To obtain the data required for training the machine learning model, a set of virtual flocs of prescribed fractal dimension was generated through a computer software. The virtual flocs were subject to chord length data acquisition by means of another piece of software simulating the operation of a focused beam reflectance probe. With the chord length data generated the random forest regression model was trained and optimized and then satisfactorily validated with data of real suspensions of known average geometry. The method developed may be used to implement flocculation control systems capable of adjusting the geometry of flocs to the requirements of subsequent concentration operations by actuating on the process stirring intensity.Graphical abstractUnlabelled Image
       
  • Elucidating the unique physiological responses of halotolerant Scenedesmus
           sp. cultivated in sea water for biofuel production
    • Abstract: Publication date: January 2019Source: Algal Research, Volume 37Author(s): Neha Arora, Lieve M.L. Laurens, Nicholas Sweeney, Vikas Pruthi, Krishna Mohan Poluri, Philip T. Pienkos Utilization of saline or sea water for large-scale cultivation of microalgae can potentially provide a leap towards the reduction of both cost and sustainability challenges for biofuel production. The present investigation evaluated the temporal changes in carbohydrates and fatty acids of a halotolerant microalga Scenedesmus sp. IITRIND2 grown in natural seawater salinity to delineate the differential physiological response towards salt stress and subsequent potential for biofuel production. The microalga showed remarkable ability to tolerate different salinity environments under given temperature and light conditions. Such tolerance was attributed to the increase in neutral sugars, such as glucose, mannose, galactose, fucose and ribose, associated with both structural and storage (and potentially osmoprotectant) polymeric carbohydrates. The carbohydrate rearrangements may aid in the remodeling of cellular components to circumvent the detrimental effects of high salinity. The observed high carbohydrate and lipid accumulation in this microalga signifies its potential for integrated bioethanol and biodiesel production. This work provides a basic understanding towards high salinity adaption of Scenedesmus sp. IITRIND2, which could further be explored for identifying targets for halotolerance in other microalgal strains.
       
  • Production of microbial biomass feedstock via co-cultivation of
           microalgae-bacteria consortium coupled with effective wastewater
           treatment: A sustainable approach
    • Abstract: Publication date: January 2019Source: Algal Research, Volume 37Author(s): Bidhu Bhusan Makut, Debasish Das, Gargi Goswami A sustainable process was demonstrated towards production of biomass feedstock coupled with wastewater treatment. Sustainability was endeavored to be achieved via symbiotic growth of microalgae and bacteria coupled with utilization of wastewater as cheap source of nutrient and water. The best microalgae-bacteria consortium comprised of two microalgae Chlorella sorokiniana strain DBWC2 & Chlorella sp. strain DBWC7 and two bacteria Klebsiella pneumoniae strain ORWB1 & Acinetobacter calcoaceticus strain ORWB3. When the consortium was characterized on artificial wastewater and raw dairy wastewater, a significant improvement in the microalgal growth, total biomass titer, chemical oxygen demand (COD), and nitrate removal efficiency was observed as compared to microalgae alone. Total biomass titer, nitrate removal, COD removal efficiency was found to be 2.84 g L−1, 93.59%, 82.27% and 2.87 g L−1, 84.69%, 90.49% in artificial wastewater and raw dairy wastewater respectively. The selected microalgae-bacteria consortium may be a potential platform towards sustainable production of microbial biomass using wastewater.Graphical abstractUnlabelled Image
       
  • Starch from the sea: The green macroalga Ulva ohnoi as a potential source
           for sustainable starch production in the marine biorefinery
    • Abstract: Publication date: January 2019Source: Algal Research, Volume 37Author(s): Meghanath Prabhu, Alexander Chemodanov, Ruth Gottlieb, Meital Kazir, Omri Nahor, Michael Gozin, Alvaro Israel, Yoav D. Livney, Alexander Golberg The growing population, decreasing arable land and fresh water supply questions the sustainability of terrestrial agriculture for securing safe nutrients supply, particularly starch- an essential ingredient for all staple foods. Here, we report the isolation, characterization and offshore production assessment of native starch from green seaweed Ulva ohnoi cultivated in seawater. Starch content varied from 1.59% to 21.44% depending on growth conditions and seasons. Our results show that nutrient starvation significantly increased the starch concentration up to 21.4% on dry weight basis. The extracted fraction contained 75.45% starch, and the starch extraction yield from the U. ohnoi biomass was 50.37%. Ulva starch granules are spherical, ovoid and irregularly shaped, 5–7 μm in size. Their gelatinization temperature is 69°C and they are susceptible to α-amylase and amyloglucosidase digestion. U. ohnoi biomass cultivated offshore for 13 months showed an average starch yield of 3.43 ton/ha/year (t·ha−1y−1). This study encourages the potential use of offshore produced biomass for sustainable starch supply as an alternative to current agricultural products, the production of which requires arable land and fresh water.Graphical abstractUnlabelled Image
       
  • Phylogenetic connection among close genera of Aphanizomenonaceae
           (Cyanobacteria): Amphiheterocytum gen. nov., Cylindrospermopsis and
           Sphaerospermopsis
    • Abstract: Publication date: January 2019Source: Algal Research, Volume 37Author(s): Célia L. Sant'Anna, Watson A. Gama, Janaina Rigonato, Gilsinéia Correa, Marcella C.B. Mesquita, Marcelo Manzi Marinho Aphanizomenonaceae is a recently proposed family of Cyanobacteria encompassing 12 planktic genera. The formation and distribution of heterocytes and akinetes along the trichome are the main morphological characteristics of this family. In this context, Sphaerospermopsis and Cylindrospermopsis are close related genera both molecularly and morphologically differing by 1) rounded akinetes adjacent to the heterocytes disposed along the trichome in Sphaerospermopsis; 2) apical heterocytes and akinetes separated by a few cells (2–3) in Cylindrospermopsis. Recently, during a survey on cyanobacteria from tropical Brazilian eutrophic lakes, strains with similarities to Sphaerospermopsis and Cylindrospermopsis were isolated. Aiming to elucidate the phylogenetic placement of these strains, we performed morphological, physiological and molecular studies. The Brazilian strains were confirmed to be closely related to Sphaerospermopsis and Cylindrospermopsis, but the phylogeny, based on 16S rRNA gene and 16S–23S rRNA intergenic region, clustered them in a well-defined clade separate from these genera. According to these results, we detailed the morphology, physiology, and phylogeny of the proposed new genus Amphiheterocytum, which showed potential to create blooms in tropical shallow lakes.
       
  • Spirulina platensis sustainable lipid extracts in alginate-based
           nanocarriers: An algal approach against biofilms
    • Abstract: Publication date: January 2019Source: Algal Research, Volume 37Author(s): R. Boutin, E. Munnier, N. Renaudeau, M. Girardot, M. Pinault, S. Chevalier, I. Chourpa, B. Clément-Larosière, C. Imbert, L. Boudesocque-Delaye Cyanobacteria and especially Spirulina platensis are recognized as abundant resources of lipids and polyunsaturated fatty acids (PUFA). The main valorization of these lipids has been the biofuel production but another approach was developed here: the investigation of S. platensis fatty acids as anti-biofilm agent for skin diseases. In fact, chronic wounds represent an important burden for occidental health care systems, and are usually related to the presence of a biofilm, especially of Candida species.In order to develop a biomimetic approach against Candida biofilm formation, free fatty acids (FFA) isolated from microalgae S. platensis were explored. Four solvents, including three bio-sourced ones, and three extraction conditions were screened. Lipid and pigment amounts, combined with FFA profiles were analyzed to select the optimal conditions: 30 min of ultrasonic extraction using dimethylcarbonate or ethylacetate as extraction solvent. A vectorization using a macroalgal-alginate nanocarrier was successfully performed. Vectorized extracts were safe towards keratinocytes and thus compatible with a topical use. Spirulina lipid-enriched extracts showed a high anti-biofilm growth activity at low concentrations (about 80% inhibition after 24 h at 0.2 mg/mL). The combination of extracts in copper-alginate nanocarriers potentiated the anti-biofilm growth activity and exhibited a good anti-biofilm activity (about 50% inhibition after 24 h at 0.1 mg/mL). The combined approach of encapsulated Spirulina lipid extracts represented thus a relevant concept to develop all in one anti-biofilm weapons against Candida and represent a new perspective for algae biomass valorization.Graphical abstractUnlabelled Image
       
  • Euglena as a potential natural source of value-added metabolites.
           A review
    • Abstract: Publication date: January 2019Source: Algal Research, Volume 37Author(s): Sreejith Kottuparambil, Roshni Lilly Thankamony, Susana Agusti Microalgae-derived functional materials, such as food supplements, drugs, and biofuels have gained a great deal of attention in recent times. Among the several microalgae investigated for biomaterials production, Euglena spp. are particularly attractive due to their easiness to grow in cultures and the ability to produce numerous bioactive compounds through extremely complex metabolic pathways. The genus Euglena comprises more than 300 species of unicellular, predominantly freshwater flagellates of worldwide distribution. The plastids in Euglena cells have been recognized as a site of the production of proteins, fatty acids, and many other value-added metabolites. Euglena is one of the few microorganisms that simultaneously produces antioxidants, such as β-carotene, l-ascorbic acid, and α-tocopherol, along with wax esters, phytotoxins and polyunsaturated fatty acids (PUFAs), that are useful in the manufacture of pharmaceuticals, cosmeceuticals, and nutraceuticals. Nevertheless, the biotechnological potency of Euglena for industrial production has been exploited limitedly. This review summarizes the major value-added compounds obtained from the protist genus Euglena and their potential and prospects for commercial production.
       
  • Differential hydrolysis of proteins of four microalgae by the digestive
           enzymes of gilthead sea bream and Senegalese sole
    • Abstract: Publication date: January 2019Source: Algal Research, Volume 37Author(s): A.J. Vizcaíno, M.I. Sáez, T.F. Martínez, F.G. Acién, F.J. Alarcón This study evaluates the in vitro protein hydrolysis of four microalgae (Tisochrysis lutea, Nannochloropsis gaditana, Tetraselmis suecica and Scenedesmus almeriensis) by intestinal proteases of gilthead sea bream (Sparus aurata) and Senegalese sole (Solea senegalensis). The hydrolysis of protein was monitored at different sampling times by electrophoretic techniques, and the quantification of the free amino acids released by proteases. Overall, S. aurata or S. senegalensis proteases hydrolysed microalgae protein in a similar way. The highest hydrolysis values (coefficient of protein degradation, CPD > 70%) were obtained for Tisochrysis and Nannochloropsis biomasses, which showed a progressive and almost complete proteolysis at the end of the in vitro assay. Tetraselmis and Scenedesmus protein was also hydrolysed, but SDS-PAGE revealed that two protein fractions remained virtually intact at the end of the in vitro assay. The final amount of free amino acids released in vitro by the fish digestive enzymes ranged from 9 to 25 g 100 g protein−1. A linear relationship between CPD and the amount of free amino acids released was found, a fact that suggests that microalgae protein is hydrolysed efficiently by the digestive proteases of both fish species. The present study provides information about the protein availability from selected microalgae, which will aid in the initial evaluation of the microalgae as potential protein sources in feeds of two important farmed fish species.Graphical abstractUnlabelled Image
       
  • Extraction and quantification of phycobiliproteins from the red alga
           Furcellaria lumbricalis
    • Abstract: Publication date: January 2019Source: Algal Research, Volume 37Author(s): Mihkel Saluri, Margit Kaldmäe, Rando Tuvikene Phycobiliproteins are natural additives in food industry and essential fluorescent probes in biotechnology. Various algal species may be suitable for their extraction, therefore, it is important to study different seaweeds to determine the highest-yielding species. Furcellaria lumbricalis, a red algal species primarily harvested from Canadian, Danish and Estonian waters, has been utilized for merely furcellaran extraction in Estonia on a commercial scale for over 50 years. To further valorize the bioresource it is vital to study whether additional products, such as phycobiliproteins, can be extracted. In the given study, optimal phycobiliprotein extraction conditions from F. lumbricalis were determined for the first time. For quantification, a novel high-pressure liquid chromatography method with fluorescence and photodiode array detection was developed. Considering R-phycoerythrin, citrate pH 6 buffer gave the highest yields (0.13% using fluorescence detector and 0.43% using photodiode array detector) after an extraction for 24 h at 20 °C. Different enzymes (cellulases, xylanases, galactosidases) and their combinations, lowering the extraction temperature or ultrasonication increased the yield further. In addition, red-coloured low-molecular fraction (with similar absorption characteristics to R-phycoerythrin) was separated. For allophycocyanin phosphate pH 6 buffer gave slightly higher yield (0.09% using fluorescence detector and 0.12% using photodiode array detector), compared to citrate or acetate buffer at the same pH. However, the tested enzyme combination, temperature variation and ultrasonication were not so advantageous for allophyocyanin recovery. The phycocyanin concentration from the red algae was below the limit of detection.Graphical abstractUnlabelled Image
       
  • Amino acid excretion from Euglena gracilis cells in dark and
           anaerobic conditions
    • Abstract: Publication date: January 2019Source: Algal Research, Volume 37Author(s): Yuko Tomita, Masahiro Takeya, Kengo Suzuki, Nobuko Nitta, Chieko Higuchi, Yuka Marukawa-Hashimoto, Takashi Osanai Euglena gracilis is a unicellular, eukaryotic alga, and is commercially used for production of food, medication, cosmetics, and dietary supplements. The algal cells are known to produce wax ester and succinate under dark and anaerobic conditions. In our study, we analysed a range of metabolites, and observed the excretion of various amino acids by E. gracilis cells. Arginine, alanine, leucine, lysine, and valine were excreted in amounts exceeding 30 mg/L into the culture medium upon anaerobic incubation for three days. Furthermore, an increase in the concentration of (NH4)2HPO4 affected the production of amino acids differently: those amino acids synthesized from glycolysis metabolites decreased, whereas those synthesized from tricarboxylic acid cycle metabolites increased with an increase in (NH4)2HPO4. Glutamate excretion was uniquely regulated by (NH4)2HPO4 concentration. Moreover, we found that the production of glutamate was regulated by the pH of the culture medium, but not by nitrogen, phosphate, and salt concentrations. These results demonstrate the ability of E. gracilis to synthesize various amino acids under dark and anaerobic conditions, and contribute valuable information for the commercial and scientific applications of fermentation of eukaryotic algae.
       
  • Inducing reversible or irreversible pores in Chlamydomonas reinhardtii
           with electroporation: Impact of treatment parameters
    • Abstract: Publication date: January 2019Source: Algal Research, Volume 37Author(s): Pierre Bodénès, Sakina Bensalem, Olivier Français, Dominique Pareau, Bruno Le Pioufle, Filipa Lopes Electroporation is investigated as a possible means to facilitate the extraction of valuable compounds from microalgae. In addition, reversible or irreversible pores on the cell membrane can be obtained by changing the PEF conditions. In this paper, we discuss the impact of PEF parameters (pulse duration, ranging from 5 to 500 μs, and electrical field amplitude, values up to 7 kV·cm−1) and biomass characteristics (cell concentration, physiology) on the treatment efficiency and energy demand to induce reversible and irreversible permeabilization. Though similar levels of maximum reversible and irreversible permeabilization were obtained for all PEF conditions, the lowest energy demand and temperature increase were found for the lowest pulse duration (5 μs) tested. To better characterize microalgae electroporation, pore characterization (size and resealing time) was assessed. Pores with a maximum radius ranging from 0.8 to 0.9 nm reseal in few seconds, and do not affect cell division capability.
       
  • Enhancing algal biomass and lipid production by phycospheric bacterial
           volatiles and possible growth enhancing factor
    • Abstract: Publication date: January 2019Source: Algal Research, Volume 37Author(s): Kichul Cho, Jina Heo, Dae-Hyun Cho, Quynh-Giao Tran, Jin-Ho Yun, Sang-Moo Lee, Yong Jae Lee, Hee-Sik Kim The concept of sustainable biodiesel production using microalgae has attracted a lot of attention as an emerging green energy technology. However, low algal biomass and lipid productivity hinder cost-effective biodiesel production. To overcome these problems, this study examined the effect of bacterial volatile compounds (VCs) on the growth and lipid production of microalga Chlorella vulgaris OW-01. The VCs of phycospheric bacteria including Hyphomonas sp., Rhizobium sp., and Sphingomonas sp. efficiently augmented algal biomass in a newly developed VCs experimental apparatus. Moreover, an apparent increase in total lipid content along with a 2.34-fold increase in productivity was observed in Hyphomonas sp. VCs–exposed algal biomass. Fatty acid methyl esters (FAME) composition also demonstrated that the algal biodiesel properties were somewhat modified by exposure to bacterial VCs. A LiOH filter-inducing CO2-removed bacterial VCs (CRBVCs) also enhanced daily growth of microalgae, as compared to the control culture (aeration), indicating that CRBVC included growth-promoting volatiles. Of those factors, volatile indole was identified as a possible algal growth enhancing factor, and it showed a higher growth-promoting effect than dimethyl disulfide and dimethyl trisulfide. Based on these results, it is speculated that the use of bacterial VCs for algal cultivation is a promising future bioprocess for the algal biomass and biodiesel production.
       
  • Electromagnetic stratagem to control predator population in algal open
           pond cultivation
    • Abstract: Publication date: January 2019Source: Algal Research, Volume 37Author(s): G. Venkata Subhash, Manjuladevi Rangappa, Sagarkumar Raninga, Venkatesh Prasad, Santanu Dasgupta, G. Raja Krishna Kumar Large scale cultivation of algae is becoming a major challenge due to the impact of biotic (grazers and predators) and abiotic (salinity, light, temperature and pH) stress factors on growth and biomass productivity. Historically, to control grazers and predators, various physical, chemical and biological methods have been used which have had detrimental effects on algae growth and environment. Continuous usage of chemicals on grazers or predators is indirectly or directly encourage the biotics to resist against the applied chemicals leads to crashing of algae by enhancing their growth. To overcome such drawbacks on the usage of chemicals in the present investigation we have demonstrated an electrocution technology (physical strategy) to control grazer population without affecting algal growth and biomass productivity. Initially under lab studies different parameters like current (A)/voltage (V) were optimized to kill grazers and algal sensitivity towards the applied current and voltage. Our results reveal that the bacteria and protozoans were more sensitive to applied current at 5–10 mA compared to algal cells which are able to tolerate lower applied current dosages. Successfully, same technology with best optimum operating conditions is translated in 1 m2 and 20 m2 open ponds with unique multi electrode assembly units.Graphical abstractLarge scale cultivation of algae is becoming a major challenge due to the impact of biotic (grazers and predators) and abiotic (salinity, light, temperature and pH) stress factors on growth and biomass productivity. Historically, various physical, chemical, and biological methods have been used to control grazers and predators, which have had detrimental effects on algae growth and environment. Continuous usage of chemicals on grazers or predators directly or indirectly encourages resistance against the same chemicals, leading to frequent algae culture crashes. To overcome these drawbacks on the usage of chemicals, in the present investigation we have demonstrated the use of an electrocution technology (physical strategy) to control grazer population without affecting algal growth and biomass productivity. Initially at the lab scale level different parameters like current (A)/voltage (V) were optimized to kill grazers and algal sensitivity towards the applied current and voltage was determined. Our results reveal that the bacteria and protozoans are more sensitive to applied current at 5–10 mA compared to algal cells which are able to tolerate higher applied current dosages. Same technology with optimized operating conditions was translated successfully in 1 m2 and 20 m2 open ponds with a unique multi-electrode assembly unit.Unlabelled Image
       
  • Biomass estimation of an industrial raceway photobioreactor using an
           extended Kalman filter and a dynamic model for microalgae production
    • Abstract: Publication date: January 2019Source: Algal Research, Volume 37Author(s): F. García-Mañas, J.L. Guzmán, M. Berenguel, F.G. Acién Production of microalgae is one of the emerging biotechnological processes due to its potential applications to produce high value-added compounds. In photobioreactors for microalgae production, the biomass concentration is a desirable variable to be measured on-line to optimize the yield of the systems. However, biomass concentration can hardly be monitored in real time. There are few expensive commercial sensors that in fact provide uncertain measurements. State estimators, also known as software sensors, are algorithms designed to estimate unmeasured (or non-easily measurable) variables of a process. In this work, a state estimator using the extended Kalman filter algorithm is developed to estimate biomass concentration for an outdoor industrial raceway photobioreactor. The state estimator is based on a dynamic model for microalgae production specifically designed for this type of photobioreactor. Results demonstrate that, despite the complex non-linear dynamics that characterise this kind of bioprocess, a state estimator can provide a relatively accurate estimation of the biomass concentration. Furthermore, a state estimator could be used to optimize the operation of industrial photobioreactors by utilizing the estimated biomass concentration for automatic control of the process.
       
  • Comparison of different photobioreactor configurations and empirical
           computational fluid dynamics simulation for fucoxanthin production
    • Abstract: Publication date: January 2019Source: Algal Research, Volume 37Author(s): Bahar Aslanbay Guler, Irem Deniz, Zeliha Demirel, Suphi S. Oncel, Esra Imamoglu Microalgae production in culture systems has been a topic of intense study for a long time. Optimization of cultivation conditions and design parameters of photobioreactors are essential for the development of economically and technically feasible algae technologies. The present study aimed to evaluate the effect of different photobioreactor (PBR) configurations on biomass and fucoxanthin production from Phaeodactylum tricornutum and to examine culture conditions by using Computational Fluid Dynamics (CFD) simulation for the photobioreactor having the maximum yield. The cells were first cultivated in three different PBRs (flat plate, airlift and stirred tank) and the maximum cell concentration of 5.94 ± 0.12 × 107 cells/ml was obtained in flat plate PBR. Also, highest fucoxanthin amount was found in the same PBR with the value of 2.43 ± 0.23 mg g−1. Flat plate PBR was simulated using CFD and the obtained results were used to evaluate mixing efficiency, flow dynamics and velocity fields. The extent of mixing was found sufficient to achieve homogenous culture medium and mean turbulent kinetic energy field suggested a homogeneous dissipation, also higher intensities of turbulence were observed around the nozzles and at the liquid-gas interphase. However, dead zones and vortex formations were observed in a small proportion of PBR. For further researches, assembling mixers or baffles into the PBR may be a feasible and effective method to improve the mixing efficiency and to prevent hydrodynamic problems. It was shown that the result of cultivation experiment had good agreement with that of CFD prediction.
       
  • Nuclear transformation of the versatile microalga Euglena
           gracilis
    • Abstract: Publication date: January 2019Source: Algal Research, Volume 37Author(s): Bishal Khatiwada, Liisa Kautto, Anwar Sunna, Angela Sun, Helena Nevalainen Euglena gracilis is a unicellular microalga studied for the production of nutraceuticals, cosmeceuticals and biofuel. Full exploitation of the organism requires the development of genetic engineering tools including a method for obtaining genetically stable transformants. In this work, Agrobacterium mediated transformation, biolistic bombardment and electroporation were explored to obtain stable nuclear E. gracilis transformants. Two 3′UTR fragments of the E. gracilis gapC gene were added at the 5′and 3′ ends of the pCambia1302 T-DNA to promote homologous integration of the transforming DNA into the genome. E. gracilis transformants growing on hygromycin plates and expressing the mgfp5 gene coding for green fluorescent protein were obtained from all three approaches. Maintenance of the transforming DNA in the nucleus was confirmed by PCR. Agrobacterium-mediated transformation yielded 10 transformants, biolistic bombardment seven and electroporation one transformant per 10,000 cells plated. Transformants from biolistic bombardment and electroporation were able to transiently express the hptII gene based on their growth on hygromycin containing plates, but this property was lost during repeated rounds of cultivation suggesting lack of (stable) integration of the transforming DNA into the Euglena genome. In contrast, Agrobacterium-mediated transformation produced stable nuclear transformants growing on hygromycin plates even after 12 rounds of cultivation. This work will pave the way for further improvement of E. gracilis strains for the production of valuable compounds.
       
  • Translocation and de novo synthesis of eicosapentaenoic acid (EPA) during
           nitrogen starvation in Nannochloropsis gaditana
    • Abstract: Publication date: January 2019Source: Algal Research, Volume 37Author(s): Jorijn H. Janssen, Packo P. Lamers, Ric C.H. de Vos, René H. Wijffels, Maria J. Barbosa The microalga Nannochloropsis gaditana is known for accumulating fatty acids, including the commercially interesting eicosapentaenoic acid (EPA) within the polar lipids (PL) and neutral lipids (NL). During microalgal growth EPA is mainly present in the PL. Upon nitrogen starvation N. gaditana accumulates large amounts of TAG in lipid bodies. The neutral lipid fraction will mainly consist of triacylglycerol (TAG). When expressed per total cell dry weight, the NL-localized EPA increased while the PL-localized EPA decreased, suggesting that EPA is translocated from the PL into the NL lipids during nitrogen starvation. Here, we elucidated the origin of EPA in NL of N. gaditana by firstly growing this microalga under optimal growth conditions with 13CO2 as the sole carbon source followed by nitrogen starvation with 12CO2 as the sole carbon source. By measuring both 12C and 13C fatty acid isotope species in time, the de novo synthesized fatty acids and the already present fatty acids can be distinguished. For the first time, we proved that actual translocation of EPA from the PL into the NL occurs during nitrogen starvation of N. gaditana. Next to being translocated, EPA was synthesized de novo in both PL and NL during nitrogen starvation. EPA was made by carbon reshuffling within the cell as well. EPA was the main fatty acid translocated, suggesting that the enzyme responsible for fatty acid translocation has a high specificity for EPA.Graphical abstractUnlabelled Image
       
  • Recovery of excreted n-butanol from genetically engineered cyanobacteria
           cultures: Process modelling to quantify energy and economic costs of
           different separation technologies
    • Abstract: Publication date: January 2019Source: Algal Research, Volume 37Author(s): Jonathan L. Wagner, Daniel Lee-Lane, Mark Monaghan, Mahdi Sharifzadeh, Klaus Hellgardt The photoautotrophic production of excreted biofuels from genetically engineered cyanobacteria and microalgae represents a new and promising alternative to conventional algal fuel technologies. N-butanol is a particularly promising fuel product, as it can be directly used in petroleum engines, and has been successfully expressed in species of Synechococcus elongates 7942 and Synechocystis sp. PCC 6803. However, the high energy requirements of recovering butanol from dilute mixtures can easily outweigh the energy content of the fuel and must be carefully assessed and optimized. Consequently, the recovery of butanol was modelled using four of the most promising butanol separation technologies (distillation, gas stripping, pervaporation and ionic liquid extraction) to calculate the minimum butanol culture concentrations required to render the process energy-positive. With a break-even concentration of only 3.7 g L−1, ionic liquid extraction proved much more efficient than the distillation base-case scenario (9.3 g L−1), whilst neither pervaporation (10.3 g L−1) nor gas stripping (16.9 g L−1) could compete on an energy basis with distillation. Despite this, due to the high costs of the ionic liquid solvent, the lowest capital costs are obtained for distillation (pilot plant scale, butanol culture concentrations of 10 g L−1), whilst pervaporation carries the lowest utility costs, as a result of its low electrical energy demand. Although currently achieved maximum n-butanol culture concentrations are significantly below the calculated break-even values for all four technologies, the present work provides an important threshold for future strain development. Moreover, the recovery of side-products from purged biomass could help to reduce the costs associated with biofuel production.
       
  • Bilateral and simultaneous accumulation of lipid and biomass in the novel
           
    • Abstract: Publication date: January 2019Source: Algal Research, Volume 37Author(s): Baoyan Gao, Luodong Huang, Feifei Wang, Ailing Chen, Chengwu Zhang A new oleaginous strain of Tetradesmus bernardii exhibiting various trophic modes was isolated from an inland water body of South China. In the present study, the biomass and lipid accumulation capacity of T. bernardii in addition to its fatty acid composition were evaluated under photoautotrophic, heterotrophic, and mixotrophic cultivation conditions. T. bernardii accumulated high lipid contents up to 65.8% of dry weight under low nitrogen conditions (1 mM) in photoautotrophic cultivation. Biomass yields under heterotrophic cultivation were much higher than in photoautotrophic cultures, while lipid contents were reduced. However, T. bernardii accumulated higher biomass yields and lipid contents (54.7% of dry weight) under mixotrophic growth and high nitrogen availability (18 mM). Thus, T. bernardii achieved maximum lipid productivity due to the bilateral and synchronous enhancement of lipid content and biomass production. The fatty acid composition of T. bernardii comprised over 70% of saturated fatty acids (i.e., palmitic acid (C16:0), stearic acid (C18:0)) and monounsaturated fatty acids (i.e., palmitoleic acid (C16:1), oleic acid (C18:1)). Specifically, the mixotrophic cultivation of T. bernardii would be the preferable means for oil-rich biomass.
       
  • Biochemical signatures of acclimation by Chlamydomonas reinhardtii to
           different ionic stresses
    • Abstract: Publication date: January 2019Source: Algal Research, Volume 37Author(s): Elia D. Charles, Howbeer Muhamadali, Royston Goodacre, Jon K. Pittman Green microalgae can acclimate over short timescales to changing environmental conditions; however, it is unclear how acclimation, or phenotypic adaptation, alters the organism's metabolism and whether there are conserved responses to different stresses. Following six weeks of exposure, Chlamydomonas reinhardtii could tolerate 100 mM Na+, 100 μM Cu2+, and 35 mM PO43− and partially tolerate 25 mM NH4+, 150 mM Na+ and 150 μM Cu2+. Acclimation was coincident with increased growth rate and reduced cellular accumulation of reactive oxygen species (ROS), which was indicative of enhanced ROS scavenging. Fourier transform infrared (FT-IR) spectroscopy demonstrated distinct metabolic fingerprints of acclimated cells for each stress condition in comparison to non-acclimated cells and to non-stressed cells. Carbon allocation varied in response to stress but also following acclimation. In particular, Na+ stress increased intracellular neutral lipid content but this response was significantly reduced in acclimated cells, while carbohydrate content was enhanced in cells acclimated to excess Cu2+. Acclimation of C. reinhardtii to Na+ allowed enhanced tolerance of multiple stresses simultaneously, while the other acclimated cell lines did not display any advantage. While acclimation of C. reinhardtii to different ionic stresses elicits distinct metabolic signatures within the cells, enhanced ROS detoxification appears to be a conserved acclimation response.
       
  • Simultaneous extraction and fractionation of omega-3 acylglycerols and
           glycolipids from wet microalgal biomass of Nannochloropsis gaditana using
           pressurized liquids
    • Abstract: Publication date: January 2019Source: Algal Research, Volume 37Author(s): Natalia Castejón, F. Javier Señoráns Microalgae are primary producers of eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids in marine environment and so they are considered promising alternative sources of omega-3 long-chain polyunsaturated fatty acids (LC-PUFAs). Nannochloropsis gaditana is an oleaginous cultivated microalga with an important content of triglycerides and polar lipids which include interesting EPA amounts. In this work, new methods using pressurized liquids for simultaneous extraction and fractionation of neutral and polar lipids from wet microalgal biomass are proposed. Pressurized liquid extraction (PLE) using different solvents, combined or not with pre-treatment of the alga with enzymes, allows one to enrich and fractionate neutral and polar lipids such as triacylglycerols, diacylglycerols, monoacylglycerols, free fatty acids and glycolipids. The use of enzymatic pre-treatment did not show a significant increase in the lipid yield, though a different fractionation of the microalgal lipids was achieved. PLE with a single solvent (hexane at 120 °C) rendered a lipid yield of 17.6%, slightly higher than the traditional Folch method (16.9%), but with a less-toxic solvent and faster extraction technique. In addition, PLE with hexane attained a high triacylglycerols fraction (17.2% ± 3.0). The optimal four-step sequential method developed using pressurized liquids reached a good fractionation characterized by a high content of glycolipids (29.2% ± 2.0) and monoacylglycerols (17.3% ± 1.9), with a lipid recovery of 14.0% ± 1.3 for the original biomass. The analysis by GC/MS of fractions obtained with each method and solvent combination, showed a different composition in fatty acids of fractionated neutral and polar lipid species, especially in saturated and omega-3 fatty acids. Therefore, the proposed fast PLE methods allow the simultaneous extraction and fractionation of the neutral and polar lipids of Nannochloropsis gaditana and produce enriched EPA fractions (up to 53%).Graphical abstractUnlabelled Image
       
  • Assessment of algal biofuel resource potential in the United States with
           consideration of regional water stress
    • Abstract: Publication date: January 2019Source: Algal Research, Volume 37Author(s): Hui Xu, Uisung Lee, André M. Coleman, Mark S. Wigmosta, Michael Wang Algae is a promising feedstock for biofuels. Because scaling up the production of algae-based biofuels consumes a significant amount of water, it is important to consider the impact it has on water stress. This study evaluates the potential for algae-derived biofuel production in the United States (US) and considers regional water stress. We used the Biomass Assessment Tool (BAT) to identify potential sites in the US that meet land, biomass productivity, and CO2 co-locating criteria. We quantify the water stress impacts of algal biofuel production in terms of water scarcity footprint using water consumption from BAT, and the water stress indicator from Available Water Remaining for the US (AWARE-US) system. We assess long-term (20 billion gal per year [BGY]) and near-term (5 BGY by 2030) renewable diesel (RD) production targets. To select suitable algae sites, we consider biomass yield and water use with and without water stress constraints. We found that ranking sites based on biomass yield results in a high water stress impact (24.5 × 103 US equivalent BGY [BGYe]) for the long-term RD target. If we instead rank sites on water use efficiency, water consumption decreases on average by 62%, with an average reduction in biomass yield of 25%. To reconcile tradeoffs between biomass yield and water stress impacts, water stress indicator (AWARE-US) that represents relative water availability by region can be applied while considering biomass yield. This strategy removes sites located in water-stressed areas and keeps high-productivity sites. For the long-term RD target, this reduces water stress impacts by 55% (13.8 BGYe) without lowering yield or 97% (24.2 BGYe) with moderately lower (4%) yield, compared to the sites ranked by biomass yield alone. The results demonstrate that incorporating water stress into energy-scale algae biofuel production planning is key to achieving synergies between biofuel yield and fresh water stress impacts.
       
  • Pulsed electric field permeabilization and extraction of phycoerythrin
           from Porphyridium cruentum
    • Abstract: Publication date: January 2019Source: Algal Research, Volume 37Author(s): Juan M. Martínez, Carlota Delso, Ignacio Álvarez, Javier Raso This paper assesses the extraction of β-phycoerythrin (BPE) into aqueous media by the application of pulsed electric field treatments (PEF) to the fresh biomass of Porphyridium cruentum.An increase in electric field strength from 2 to 10 kV/cm, or a prolongation of treatment time increased electroporation and inactivation of P. cruentum in the range investigated (2–10 kV/cm; 30–150 μs). A perfect agreement between fraction of dead cells and fraction of electroporated cells was observed when more than 20% of the cells were inactivated. Even after 48 h of incubation, BPE was not detected in the extraction medium containing untreated cells of P. cruentum: thus, an intact cytoplasmic membrane prevented the exit of BPE. After 24 h of extraction, the entire BPE content (32 mg/g d.w.) was released after treating P. cruentum cells at 8 or 10 kV/cm for 150 μs. However, BPE was not released immediately after the PEF treatment, thereby requiring, in most cases, a lag time of over 6 h until the compound could be detected in the extraction medium. This behavior indicates that BPE extraction requires not only the diffusion of the compound across the cell membrane, but also the dissociation of the compound from the cell structures. In this sense, it is hypothesized that P. cruentum autolysis triggering by PEF could be the main cause involved in the effectivity of these treatments in BPE extraction. An improved grasp of the kinetics and the mechanism of the enzymes participating in microalgae autolysis, and of the autolysis trigger by PEF, will allow this process to be developed at an industrial scale.
       
  • Comparison of fatty acid composition and positional distribution of
           microalgae triacylglycerols for human milk fat substitutes
    • Abstract: Publication date: January 2019Source: Algal Research, Volume 37Author(s): Yongjin He, Tao Wu, Han Sun, Peipei Sun, Bin Liu, Mingfan Luo, Feng Chen Microalgae are renewable and valuable natural sources of triacylglycerol (TAG) for nutritional application or specific purposes. The aim of this study was to evaluate the TAGs produced by twelve microalgae species for production of human milk fat substitutes (HMFs). The investigated species were Chlorella vulgaris (CV-15 and CV-395), Chlorella zofingiensis, Chlorella pyrenoidosa, Scenedesmus sp., Chlorococcum sp., Nitzschia laevis, Phaeodactylum tricornutum, Isochrysis sp., Isochrysis galbana, Nannochloropsis oceanica and Nannochloropsis salina. The total fatty acids (TFAs) contents of these species varied from 15.9 to 31.1%. TAG was the main lipid class (65.1–91.0%). Based on the evaluation model in view of the fatty acid composition and positional distribution of TAGs by GC–MS and 13C NMR, among the tested species, Isochrysis-derived TAGs mimicking human milk TAGs (HMTs) gave the highest G values (deducting score) that were close to that of lard. The G value (69.2) of Isochrysis sp. TAG was within the range of G value for local infant formulas; whereas, the G value (61.2) of I. galbana TAG was a bit lower than the lower limit of local infant formulas. Moreover, the melting and crystallization properties of TAGs from Isochrysis sp. and I. galbana were similar to those of HMTs. These results showed that Isochrysis TAGs could be promising candidates for HMFs feedstock.Graphical abstractUnlabelled Image
       
  • Influence of successive and independent arrangement of Kenics mixer units
           on light/dark cycle and energy consumption in a tubular microalgae
           photobioreactor
    • Abstract: Publication date: January 2019Source: Algal Research, Volume 37Author(s): Chao Qin, Jing Wu The design of mixers in tubular photobioreactors is a key part to reduce the cost of microalgal culture. There have been several investigations of the static Kenics mixer in tubular photobioreactors, but how to use it efficiently has been rarely reported. In this work, the efficiency of light/dark cycle enhancement, defined as the ratio of the dimensionless increment of light/dark cycle frequency to the dimensionless increment of energy consumption, is introduced to evaluate economic aspects of adding a mixer. Then, the 4-unit Kenics mixer consisting of four successive left-right-twisting units and 1-unit Kenics mixer consisting of only one unit are compared in terms of the efficiency using computational fluid dynamics, which shows that an increase of the unit number (from 1 to 4) does not bring a considerable improvement (36%), and thus a much lower efficiency. Finally, two approaches to increasing the efficiency are developed. One is to adjust the boundary of light and dark zones in the tube to approximate the high vorticity region, and the other is to adopt more effective types of arrangement of units (e.g., the interval arrangement, instead of the already-existing successive arrangement).
       
  • Temperature dependent growth rate, lipid content and fatty acid
           composition of the marine cold-water diatom Porosira glacialis
    • Abstract: Publication date: January 2019Source: Algal Research, Volume 37Author(s): Jon Brage Svenning, Lars Dalheim, Hans Christian Eilertsen, Terje Vasskog In this study, the northern cold-water marine diatom Porosira glacialis was cultivated in a pilot-scale mass cultivation system at 5 different temperatures (−2 to 12 °C), in order to evaluate temperature-dependent growth rate (in vitro Chl a), lipid content (Folch's method) and fatty acid (FA) composition (GC–MS) in the exponential growth phase. We found that P. glacialis has a wide temperature range, with maximum growth at 12 °C and positive growth even at sub-zero water temperatures. The lipid content was inversely correlated with temperature, peaking at 33.4 ± 4.0% at 2 °C, and was highly desaturated independently of temperature; PUFA content varied from 71.50 ± 0.88% at 12 °C to 82 ± 0.64% at −2 °C. EPA was the main FA at all temperatures (31.0 ± 0.7–40.4 ± 1.2% of total FAs).
       
  • Metabolic engineering of cyanobacteria for photoautotrophic production of
           heparosan, a pharmaceutical precursor of heparin
    • Abstract: Publication date: January 2019Source: Algal Research, Volume 37Author(s): Aditya Sarnaik, Mary H. Abernathy, Xiaorui Han, Yilan Ouyang, Ke Xia, Yin Chen, Brady Cress, Fuming Zhang, Arvind Lali, Reena Pandit, Robert J. Linhardt, Yinjie J. Tang, Mattheos A.G. Koffas Heparosan is an unsulfated polysaccharide potentially important for its wide range of cosmetic and pharmaceutical applications, particularly as the precursor for the extensively used anticoagulant, heparin. Generally sourced from animals, commercially available heparin may encounter various immunological and contamination risks. Thus, safe and sustainable microbial platforms could serve as an alternative heparin source. Synechococcus, due to their fast photoautotrophic growth, strong sugar phosphate metabolisms and generally regarded as safe (GRAS) nature, may serve as photo-biorefineries for manufacturing heparosan. In this study, we have synthesized an integrative plasmid pUPm48 for cloning galU and PmHS2 genes in Synechococcus elongatus PCC 7942. The engineered recombinants (pgp7942) exhibited significant production of heparosan under different culture conditions, where the products were present in both supernatant and cell biomass. The maximum yield of 0.7 ± 0.2 μg/g-DCW (dry cell weight) and a titer of 2.8 ± 0.3 μg/L was achieved by pgp7942 under shake flask and continuous light conditions. Large scale plastic-bag cultures with natural diurnal light exhibited heparosan production of 0.5 μg/g-DCW with a titer of 0.44 μg/L. The analysis also found PCC 7942 encodes a promiscuous uridyltransferase for UDP-glucose synthesis and naturally produces multiple glycosaminoglycans including chondroitin sulfate (CS). This study demonstrates for the first-time cyanobacteria as a promising photoautotrophic refinery for producing a high-value polysaccharide commonly from animals.
       
  • Macrofiltration-A leap towards high efficiency microalgal harvesting: A
           case study using Scenedesmus acuminatus
    • Abstract: Publication date: January 2019Source: Algal Research, Volume 37Author(s): Jingrong Xiao, Rui Liu, Li Yang, Qiang Hu, Xuezhi Zhang In order to develop efficient membrane based harvesting techniques to accelerate microalgal commercialization, macrofiltration membranes of mixed cellulose with pore sizes of 0.45, 1.2, 3, 5, and 8 μm were evaluated for Scenedesmus acuminatus harvesting. The influences of pore size on the changes in membrane flux and flux recovery were investigated, followed by a SEM analysis of the fouled membranes. The performance of S. acuminatus harvesting using the 5 μm membrane was then compared with an ultrafiltration membrane, with both operating under a cross-flow mode. Macrofiltration operated with dead-end mode was further developed to achieve higher flux and higher solid content in the harvested biomass. The results showed that the 5 μm mixed cellulose membrane achieved the highest average flux due to its excellent anti-fouling performance. SEM images revealed that the presence of non-cellular and cellular foulants were responsible for the fouling of the smaller sized membranes, and membranes larger than 5 μm, respectively. Macrofiltration membrane harvesting was more efficient when a dead-end rather than a cross-flow operation was used. The average flux from a multiple-times filtration cycle reached 1845 ± 105 L·m−2·h−1 for the dead-end operated 5 μm macrofiltration membrane, which was 16-fold higher than that obtained using a cross-flow ultrafiltration membrane (107 ± 14 L·m−2·h−1). The solid content of macrofiltration-harvested biomass was 24%. This high flux and high solid content achieved through macrofiltration represents a great leap towards high-efficiency microalgal harvesting.
       
  • Microencapsulation of algal biomass (Tetraselmis chuii) by spray-drying
           using different encapsulation materials for better preservation of
           beta-carotene and antioxidant compounds
    • Abstract: Publication date: December 2018Source: Algal Research, Volume 36Author(s): Felipe de Jesús Bonilla-Ahumada, Sanghamitra Khandual, Eugenia del Carmen Lugo-Cervantes The awareness of harmful effects of synthetic compounds and an inclination towards the usage of natural products have led to the exploitation of microalgae as a source of natural colors. Because of their health benefits, algal pigments have massive commercial value as natural colorants in the nutraceutical, cosmetics, and pharmaceutical industries. One of the important natural sources of microalgae are antioxidants, bioactive components: such as polyunsaturated fatty acids, β-carotene, sulfated polysaccharides and sterols. However, these antioxidant-rich fractions and carotenoids possess low storage stability and exhibit high sensitivity to light, heat, and oxygen. During the extraction process, there is some loss of required materials, and also, chances of the contamination from toxic solvents. There are few reports on algal-extract encapsulation and algal biomass encapsulation, and only a few types of wall materials that can show better stability, shelf life, and controlled release have been investigated.In this work, we investigated micro-encapsulation of the fresh algal biomass of Tetraselmis chuii and studied the effect of the wall material and the processing conditions of the spray dryer on the preservation of β-carotene and antioxidant compounds. Our studies revealed that a native species of Tetraselmis from Mexico, which is an important aquaculture feed, produce a considerable amount of β-carotene as much as 1.3% of its biomass. We found preservation of 80–92% of beta-carotene and 46–81% phenolic-compounds in freshly microencapsulated microalgae even after three months of storage in dark condition at 25 °C, maltodextrin at 130 °C was found the best wall material. This alga is suitable for use in aquaculture and food industry because fresh microalgae can be microencapsulated without loss of its nutritional values, and it is easier to handle and transport. This can serve as a functional food with better preservation of its antioxidant value and can be processed without any toxic solvent component.
       
  • Pretreatment and fermentation of salt-water grown algal biomass as a
           feedstock for biofuels and high-value biochemicals
    • Abstract: Publication date: December 2018Source: Algal Research, Volume 36Author(s): Eric P. Knoshaug, Tao Dong, Ryan Spiller, Nick Nagle, Philip T. Pienkos Utilization of halotolerant algal strains and saline water resources is necessary to increase the areas available for algal cultivation and to mitigate fresh water use issues. However, the added salt content from salt-water algae cultivation may impact downstream biomass pretreatment and conversion processes especially when combined with the salt that is generated as part of our Combined Algal Processing (CAP) scheme which includes pretreatment with sulfuric acid for cell disruption and carbohydrate hydrolysis. Here we compared the pretreatment, fermentation, and lipid extraction processes on salt-water versus fresh-water grown algal biomass. Response surface pretreatment plots showed that a broader range of conditions for the salt-water grown algae species yield>90% sugar yield compared to a narrower range for fresh-water species. Despite this, we anticipated that high salt content would inhibit fermentation of algal sugars, a key element the CAP scheme and sought to reduce the formation of additional salt from pretreatment and neutralization by substituting oxalic acid for sulfuric acid. The sugar release response surface for oxalic acid was of a different shape than that of sulfuric acid but achieved>90% sugar release at 2% acid. Fermentation results showed that for Saccharomyces cerevisiae, the added salts had minimal impact on sugar utilization rates or ethanol production. For Actinobacillus succinogenes however, a significant delay was observed due to the additional salts and fermentation was further delayed or inhibited by pretreatment with oxalic acid. This was remedied by removal of the oxalic acid either by the addition of CaCO3 or trioctylamine whereupon fermentation rates recovered. Differences in lipid extraction yields were observed from the fermentation broth between the salt-water grown and fresh-water grown algal biomass and was species dependent.
       
  • Bioenergy from wastewater resources: Nutrient removal, productivity and
           settleability of indigenous algal-bacteria polyculture, and effect of
           biomass composition variability on methane production kinetics and
           anaerobic digestion energy balance
    • Abstract: Publication date: December 2018Source: Algal Research, Volume 36Author(s): Pavlo Bohutskyi, Ruth E. Spierling, Duc Phan, Anatoliy M. Kopachevsky, Yuting Tang, Michael J. Betenbaugh, Edward J. Bouwer, Trygve J. Lundquist Algal-bacteria high-rate ponds represent an energy-efficient wastewater treatment approach and a source for affordable and sustainable biomass feedstock for production of renewable energy through anaerobic digestion (AD). However, there is still a need for more data on wastewater treatment efficiency, biomass productivity and settleability from outdoor treatment facilities, as well as on impact of variability in biomass composition and digestibility on methane yield and energy output. Hydraulic retention time (HRT) and wastewater quality fed into 30 m2 raceway ponds had a major effect on algal-bacteria polyculture productivity, settleability, phylogenetic and biochemical compositions, digestibility and methane yield. While Micractinium, Scenedesmus, Chlorella, and pennate diatoms were always among the key species observed, the gross productivity and 2-hour settleability during summer cultivation varied in the first-stage ponds treating primary wastewater from 29 ± 5 to 54 ± 12 gAFDW/m2/d and from 88 ± 8 to 94 ± 4% for HRT of 3 and 2 days, respectively. For these conditions, the effluent had csBOD of 3.4 or 3.3 mg/L and Ntotal (mostly NO3−-N) of 9.2 or 8.2 mg/L, respectively. The second-stage algal ponds (HRT 3 days) showed lower productivity of 16 ± 6 gAFDW/m2/d, settleability of 84 ± 11%, and effluent csBOD 3.7 mg/L and Ntotal 0.8 mg/L. Biomass composition from different ponds was 34–38% protein, 18–28% total lipids and 6–14% FAME. The methane yield varied about 30% with largest value of 0.34 ± 0.01 L/gVS and showed a positive correlation with biomass lipid content (R2 = 0.93). First-order and pseudo-parallel first-order rate kinetic models exhibited a better fit for methane production (most R2 > 0.993) than the modified Gompertz model. The variation in biomass composition led to significant differences in energy output (varied by about 60%), Net Energy Ratios (ranged from 1.6 to 2.2) and Net Energy Efficiency (from 60% to 70%) when projecting the energy balance for a large-scale continuous AD process with an optimal HRT of 20–30 days.Graphical abstractUnlabelled Image
       
  • Extraction and fractionation of microalgae-based protein products
    • Abstract: Publication date: December 2018Source: Algal Research, Volume 36Author(s): Laura Soto-Sierra, Petya Stoykova, Zivko L. Nikolov Microalgae are a valuable source of proteins that can be utilized as functional, nutritional and therapeutic commodities. While process optimization and integration are still required to extend commercial applications, diverse approaches have been taken to process and characterize microalgae-derived protein products, such as protein concentrates, hydrolysates, and bioactive peptides. This review presents the current status of extraction and fractionation of protein products from microalgae and provides recommendations on: (1) processing factors (drying, cell disruption and enzymatic hydrolysis) that could affect protein release, functional properties, and extraction yield; (2) scalability and efficiency of fractionation processes for the production of protein concentrates, hydrolysates, and bioactive peptides; (3) techno-economic feasibility of algal-derived protein products; and (4) opportunities, challenges, and recommendations for further development of microalgal protein industry.Graphical abstractUnlabelled Image
       
  • A new dimension in algal cultivation – 3D printed structures with a
           range of buoyancies
    • Abstract: Publication date: December 2018Source: Algal Research, Volume 36Author(s): Christina Praeger, Rocky de Nys The free-floating cultivation of macroalgae is a fundamental requirement for the efficient bioremediation of land-based waste streams as this cultivation mode fully utilises the water column available for production, translating to improved areal biomass productivities. To achieve the free-floating cultivation of species grown from propagules and dependent on the attachment to surface structures, we have used 3D printed structures made of polymers with negative, neutral and positive buoyancies to investigate the potential to manipulate the position in the water column for cultivation. Small wheel-shaped structures with internal protected spokes were designed, manufactured and seeded with zoids of Ulva tepida. Their settlement was quantified at different locations of the settlement structure and, although similar across polymer types, approximately 80% less zoids were on the outside of the wheel shaped structures made of polyethylene compared to protected locations 3 days post-seeding. Subsequently, all structures were maintained over 31 days as free-floating cultures under outdoor cultivation in aerated buckets and paddle wheel driven high rate algal ponds (HRAPs). Both negatively and positively buoyant polymers maintained their buoyancies with increasing algal biomass over time in the static test, while the neutrally buoyant polymer showed the highest variation and became exclusively positively buoyant after 14 days of cultivation. Productivities were generally higher and more variable in aerated buckets ranging up to 28.4 ± 1.7 g dw m−2 day−1, than in HRAPs ranging up to 18.9 ± 3.9 g dw m−2 day−1. There was no clear effect of polymer type, and consequently buoyancy, on algal productivity. Similarly, all tested polymers had maximum productivities between 12 and 22 days for cultivation in aerated buckets and 7–17 days in HRAPs. This study highlights the potential to use 3D printing to create settlement structures with a range of buoyancies for land-based cultivation.
       
  • Potential of a liquid foam-bed photobioreactor for microalgae cultivation
    • Abstract: Publication date: December 2018Source: Algal Research, Volume 36Author(s): Agnes Janoska, Vasilis Andriopoulos, Rene H. Wijffels, Marcel Janssen The liquid foam-bed photobioreactor is a novel photobioreactor for microalgae cultivation. A mathematical model was developed to evaluate its potential, and to optimize the design and operation of a large-scale unit. This model describes light limited microalgal growth in a rising foam column in a foam-bed photobioreactor, which is continuously operated at constant biomass density. The microalgae-containing liquid is recirculated from the bottom of the reactor and dispersed equally on the top of the foam column, in order to ensure homogenous microalgae distribution and a wet and stable foam. The model combines calculations of liquid fraction gradient, light penetration, microalgal growth, and gas transfer in the foam-bed. The liquid fraction and light model was experimentally validated. The areal productivity of a 5 cm deep foam-bed photobioreactor operated at 30 g L−1 microalgae and 1500 μmol photons m−2 s−1 was estimated to be 67.7 g m−2 d−1. This productivity is slightly lower compared to what is achievable in flat panels, which is related to light scattering in the foam-bed. Nevertheless, the advantages of the foam-bed photobioreactor, such as high gas transfer rate and high biomass densities, were confirmed with the simulations. In addition, it was calculated that a CO2 uptake efficiency of 97% can be obtained ensuring minimal CO2 loss. These benefits result in reduced gas supply requirement and reduced energy required for downstream processing. The total energy required for the production and separation of 1 g biomass in liquid foam-beds is only 8.5% of what is required in flat panels with suspended biomass. These results highlight the potential of foam-bed photobioreactors for large scale application for microalgae production.
       
  • Selective production of the acyclic monoterpene β-myrcene by
           microplantlet suspension cultures of the macrophytic marine red alga
           Ochtodes secundiramea under nutrient perfusion cultivation with
           bromide-free medium
    • Abstract: Publication date: December 2018Source: Algal Research, Volume 36Author(s): Jason Polzin, Gregory L. Rorrer This study demonstrated the selective production of a single acyclic monoterpene, β-myrcene, by photosynthetic, clonal microplantlet suspension cultures of the macrophytic red alga Ochtodes secundiramea (Cryptonemiales, Rhizophyllidaceae). Microplantlets were cultivated within an airlift photobioreactor under continuous medium perfusion with enhanced nutrients (nitrate, phosphate) and 3500 ppm CO2 in the aeration gas to provide nutrient-replete conditions. The removal of bromide (Br-) and vanadate (VO43−) from the medium shut down bromoperoxidase-catalyzed halogenation, so that only the common precursor to halogenated monoterpenes, β-myrcene, accumulated within the biomass. Nutrient-replete cultivation enabled near-exponential biomass production to density of 6 g DW/L, with specific growth rate of 4.4 ± 0.1% per day over the 36 day cultivation period at near-saturation light intensity. Myrcene was produced during biomass production, and the specific rate of β-myrcene production within the biomass exceeded the specific rate of biomass production, so that β-myrcene accumulated within the biomass. Increasing the mean light intensity from approximately 60 to 95% of light saturation linearly increased the growth rate, but did not increase the specific rate of β-myrcene production. At near saturation light intensity, the specific rate of β-myrcene production was 6.8 ± 0.7% per day (1.0 S.E.) with yield of 40 μmol/g DW after 36 days. Although the yields of β-myrcene were low (0.6 wt% in biomass), the potential for high biomass density, ease of microplantlet separation, and high selectivity of hydrocarbon biosynthesis suggest that microplantlets of terpenoid-producing red macroalgae have promise as a new platform for advanced hydrocarbon biofuel production from CO2, provided new strategies can be developed to enhance monoterpene yield.
       
  • Fouling in microalgal membrane bioreactor containing nitrate-enriched
           wastewater under different trophic conditions
    • Abstract: Publication date: December 2018Source: Algal Research, Volume 36Author(s): Azadeh Babaei, Mohammad Reza Mehrnia The present study examined fouling in a microalgal membrane bioreactor under mixotrophic, heterotrophic and photoautotrophic conditions. N-enriched wastewater, containing nitrate source, was used as a nutrient source for cultivation of microalgae. The results confirmed that the membrane fouling rates increased under mixotrophic cultivation through enhanced production of carbohydrates in soluble microbial products (SMPc) and protein in extracellular polymeric substances (EPSp). The transmembrane pressure (TMP) jumping was observed under mixotrophic and photoautotrophic cultivation after 31 and 47 days of operation, respectively, while the TMP of heterotrophic cultivation did not exceed 10 kPa throughout 51 days. The highest EPSp was produced under mixotrophic condition due to high nitrogen removal rate. Also, the results of resistance analysis indicated that cake resistance was the main fouling resistance in all cultivation types and the latter result was confirmed by SEM analysis. In addition, higher protein fraction of cake layer on membrane foulants in comparison to carbohydrates fraction increased the hydrophobicity of membrane's surface in all cultivations (except heterotrophic culture). Compared to mixotrophic and photoautotrophic cultures, hydrophobic properties and cell size of heterotrophic microalgae increased and resulted in low membrane fouling rates.Graphical abstractUnlabelled Image
       
  • Characterization of the Nannochloropsis gaditana storage carbohydrate: A
           1,3-beta glucan with limited 1,6-branching
    • Abstract: Publication date: December 2018Source: Algal Research, Volume 36Author(s): Brian W. Vogler, Jacob Brannum, Jeffrey W. Chung, Mark Seger, Matthew C. Posewitz As a result of a secondary endosymbiosis of a red alga, stramenopiles retained β-1,3 glucans as the primary soluble storage carbohydrate, in contrast to the starch and glycogen of green plants and animals. This storage carbohydrate has been identified and characterized in representative diatoms, brown algae, and oomycetes, but has not been biochemically characterized in species of Nannochloropsis, an industrially relevant genus of algae favored for its lipid content and productivity. In this study, the soluble storage carbohydrate of Nannochloropsis is characterized by 1H NMR, linkage analysis, and size exclusion chromatography. The putative genes encoding enzymes required for synthesis of the carbohydrate oligosaccharide from glucose 6-phosphate are identified. A glycogenin-like glycosyltransferase family 8 (GT8) protein was also identified to be conserved among all species of Nannochloropsis, despite the lack of glycogen in the genus. Homologs were identified in available genomes of brown algae, diatoms, and oomycetes, all documented to utilize β-1,3 glucans for carbon storage. Finally, a set of three likely laminarinases are highlighted from the glycosyl hydrolases by phylogenetic analyses.
       
  • Ulvan lyase from Formosa agariphila and its applicability in
           depolymerisation of ulvan extracted from three different Ulva species
    • Abstract: Publication date: December 2018Source: Algal Research, Volume 36Author(s): Venkat Rao Konasani, Chunsheng Jin, Niclas G. Karlsson, Eva Albers Members of green macroalgae cause green tides in eutrophicated coastal waters. These green tides pose an environmental issue and an economic burden on coastal municipalities. The biomass from these green tides has a potential to be used as feedstock in biorefinery due to the content of interesting biomacromolecules. Ulvan, an anionic water-soluble polysaccharide, is one of such components, and its depolymerisation to high-value oligosaccharides or fermentable monosaccharides would bring value to green tide biomass which is otherwise left to decompose. However, only a few ulvan depolymerising enzymes are studied to date. Ulvan lyases depolymerise ulvan, via the β-elimination mechanism, leading to release of oligosaccharides with an unsaturated 4‑deoxy‑l‑threo‑hex‑4‑enopyranosiduronic acid at the non-reducing end. In this study, we have identified the presence of two different domains, a catalytic and a non-catalytic, in a putative ulvan lyase from Formosa agariphila KMM 3901. We overexpressed, purified, and biochemically characterised the full-length ulvan lyase, which was found to be most active at a temperature of 45 °C and pH 8.5. It exhibited high specificity for ulvan and did not degrade heparan sulphate, chondroitin sulphate, alginate, pectin or xanthan. Detailed analyses of end products of the enzymatic degradation of ulvan using 1H NMR and LC-MS revealed a disaccharide with an unsaturated uronic acid (∆) linked to 3‑sulphated rhamnose (Rha3S), trisaccharide with xylose (Xyl) flanked by Rha3S (Rha3S-Xyl-Rha3S), tetrasaccharide with an unsaturated uronic acid at the non-reducing end (∆Rha3S-Xyl-Rha3S) and pentasaccharides (Rha3S-Xyl-Rha3S-Xyl-Rha3S and branched ∆Rha3S-Xyl-(∆)Rha3S) as the principal end products. We also found that the catalytic domain that lacks the non-catalytic carbohydrate binding module exhibited higher affinity for the soluble ulvan and efficiently depolymerised it. This study reveals the characteristics of the endolytic ulvan lyase, which is a member of the ulvan utilisation loci in Formosa, and points towards the potential ulvan depolymerisation applications in Ulva biorefinery.
       
  • Continuous harvesting of microalgae biomass using foam flotation
    • Abstract: Publication date: December 2018Source: Algal Research, Volume 36Author(s): Muayad A.S. Alkarawi, Gary S. Caldwell, Jonathan G.M. Lee Biomass harvesting and dewatering are major operational costs that constrain the development and expansion of the industrial use of microalgae; particularly for low value biofuels. In this study we demonstrate, for the first time, a surfactant-aided foam flotation column that is designed and optimised for the continuous harvest of microalgae not only to improve the productivity of microalgae biomass but also as an attempt to overcome the trade-off between recovery efficiency and enrichment in batch and semi-batch foam flotation. The following operational parameters were optimised; surfactant concentration, air flow rate, feed flow rate, column height, liquid pool depth, and sparger type. Additionally, the effects of cell surface characteristics (hydrophobicity, zeta potential, and contact angle) were investigated on Chlorella vulgaris flotation performance. Hydrophobicity was enhanced using three surfactants; the cationic cetyltrimethylammonium bromide (CTAB), the anionic sodium dodecyl sulphate (SDS), and the non-ionic TWEEN®20; with CTAB producing the greatest enhancement. Surfactant concentration, column height, and air flow rate had the greatest effect on the algae concentration factor (CF) and recovery efficiency (RE). The optimised design (CTAB = 35 mg L−1, air flow rate = 1 L min−1, feed flow rate = 0.1 L min−1, column height = 146 cm, liquid pool depth = 25 cm, with a fine porous sparger) yielded RE of 95, 93, and 89% with 173, 271, and 143-fold biomass enrichments for freshwater C. vulgaris and marine Isochrysis galbana and Tetraselmis suecica microalgae respectively. Achieving high RE for freshwater and in the case of marine microalgae (irrespective of ionic strength) at moderate surfactant dosages, gives foam flotation the advantage of being a growth media independent harvesting process. The process had a very low power consumption (0.052 kWh m−3 of algae culture). Our findings demonstrate the potential for continuous, low cost, scalable flotation harvesting with particular relevance for the biofuels, water and wastewater treatment industries.
       
  • Recombinant Synechococcus elongatus PCC 7942 for improved zeaxanthin
           production under natural light conditions
    • Abstract: Publication date: December 2018Source: Algal Research, Volume 36Author(s): Aditya Sarnaik, Vishnu Nambissan, Reena Pandit, Arvind Lali Cyanobacteria are globally recognized as potential photosynthetic platform cell factories for production of value-added chemicals. Carotenoids are industrially important fine chemicals used in food, pharmaceutical and health-care products. Zeaxanthin has emerged as a high value xanthophyll carotenoid that exhibits superior antioxidant properties over many other carotenoids. Traditionally sourced from plants like marigold flowers wherein, zeaxanthin co-occurs with lutein. Therefore, there is a need for isolated production system for zeaxanthin on account of difficulties in separation of zeaxanthin from lutein due to their very similar molecular structures. Synechococcus elongatus PCC 7942 (PCC 7942) is a cyanobacterium that is known to synthesize zeaxanthin as one of the predominant cellular carotenoids and does not possess pathway genes for lutein production. In order to construct a system capable of industrial production of zeaxanthin, we genetically modified PCC 7942 (Synechococcus 79R48) to improve β‑carotene flux towards zeaxanthin synthesis by cloning CrtR (β‑carotene oxygenase) gene from Synechococcus elongatus PCC 7002 through homologous recombination. This strategy effectively enhanced the yield (mg/g DCW) of zeaxanthin in the transformants. Moreover, to increase zeaxanthin titer (mg/L), an operon construct was synthesized where a heterologous gene GalP (Hexose-H+ symporter) from E. coli MG1655 was cloned downstream of CrtR (Synechococcus 79RG48) which facilitated inherently obligate photoautotrophic WT PCC 7942 cells to uptake extracellular glucose in transformants, thereby increasing biomass productivity. Autotrophically grown cells yielded 9.02 ± 1.10 mg/g DCW of zeaxanthin while under mixotrophy the yield was 8.09 ± 0.19 mg/g DCW, which was 2-fold improvement over the wild type. The volumetric productivities of the transformants were 1.18 ± 0.17 mg/L·d and 1.8 ± 0.06 mg/L·d under autotrophic and mixotrophic conditions, respectively while WT produced 0.58 ± 0.02 mg/L·d. The work was successfully able to demonstrate that the modifications resulted in, enhanced production of lutein-free zeaxanthin in the cyanobacterial system.
       
  • Effects of selenite on growth, photosynthesis and antioxidant system in
           seaweeds, Ulva fasciata (Chlorophyta) and Gracilaria lemaneiformis
           (Rhodophyta)
    • Abstract: Publication date: December 2018Source: Algal Research, Volume 36Author(s): Zhiwei Liu, Qing Wang, Dinghui Zou, Yufeng Yang Selenium (Se) is an essential trace element for plants, animals and humans. Se enrichment has been deemed as a new approach to enhance the nutrient and economic value of seaweed to make it commercially competitive. To explore the effects of Se on seaweed photosynthesis, Ulva fasciata (Chlorophyta) and Gracilaria lemaneiformis (Rhodophyta) were cultured over 1 week in selenite (Na2SeO3) concentrations of 0, 200, 500, 800 mg L −1. Our results showed that, U. fasciata and G. lemaneiformis effectively accumulated Se and transformed inorganic Se to organic Se at the rate of about 80% during cultivation. Se exerted positive effect on growth and photosynthesis in the three Se concentrations (200, 500, 800 mg L−1 selenite) with the optimum concentration 200 mg L−1 in Ulva and 500 mg L−1 in Gracilaria, and Se promoted growth of seaweeds Gracilaria and Ulva, accumulating more soluble protein (SP) and carbohydrate (SC). Also, photosynthesis was improved by promotion of photosynthetic pigments (Chl a, Car, PE, PC), stimulation of photosystem II (PSII) (Fv/Fm, a, rETRm), and enhancement of photosynthetic oxygen evolution (Pn, AE). In addition, Se stimulated activities of SOD, POD, CAT and GPX with all Se concentrations in Ulva and Gracilaria, and substantially decreased MDA levels in 200 mg L−1 selenite, indicating that Se could increase antioxidative activity and enhance antioxidant system. We proposed that enhanced defensive system of antioxidants by Se could improve and protect photosynthesis to some extent.
       
  • Metabolite profiling, antioxidant, scavenging and anti-proliferative
           activities of selected tropical green seaweeds reveal the nutraceutical
           potential of Caulerpa spp.
    • Abstract: Publication date: December 2018Source: Algal Research, Volume 36Author(s): Bhakti Tanna, Babita Choudhary, Avinash Mishra Nutraceuticals are an important ingredient of functional foods that provide health and medicinal benefits, and are recommended for daily food intake. Seaweeds are highly nutritional and considered a rich source of antioxidants, sugars, fatty acids, essential amino acids, flavonoids, phenolics, and other secondary metabolites. Green seaweeds are distributed worldwide and tropical, green algae including Caulerpa spp. could be potentially explored as a functional food. Seven abundant tropical green seaweeds (four Caulerpa species, two Ulva species, and one native Codium species) were harvested from the Saurashtra Coast (Arabian Sea, Gujarat, India) and their metabolite profiling, total flavonoid and phenolic content, and antioxidant, scavenging, reducing, and anti-proliferative activities were examined. Liquid chromatography-mass spectrometry identified remarkable metabolites, including malvidin, kaempferol, cyanidin, quercetin, apigenin, lutein, and myricetin; ninety-seven metabolites were detected by gas chromatography–mass spectrometry. Approximately forty distinct metabolites were quantified, whereas fifty-seven metabolites were detected in more than one seaweed. Fourteen unique metabolites were detected in C. scalpelliformis, which also contained notable amino acids. Caulerpa spp. (CRM: C. racemosa var. macrophysa, CRC: C. racemosa var. cornyphora, and CS: C. scalpelliformis) showed potential total antioxidant activity (>50%), and the highest potential scavenging activity (>60%) was found in CRM followed by CS and CRC extracts. CRM and CS extracts also showed maximal reducing activity (>78%). A low half maximal effective concentration (EC50) for different biochemical activities was determined for Caulerpa spp., especially CRM (total antioxidant: 150.8 ± 5.7, scavenging: 560 ± 2, and reducing: 86.4 ± 3.1 μg ml−1) compared to other select seaweeds. CRC, CRM, and CS showed significantly high total phenolic contents, 29.2 ± 2.4, 25.0 ± 3.2 and 23.8 ± 3.3 mg gallic acid equivalent (GAE) g−1 extract, respectively. Similarly, a high total flavonoid content was detected in CS (769 ± 33 mg quercetin-equivalent g−1 extract) followed by CRC (562 ± 44), and CRM (523 ± 60). All activities (total antioxidant, scavenging, and reducing) were positively correlated with each other and also with total phenolic and flavonoid contents. Principal component analysis confirmed that CRC is a rich source of phenolic and flavonoid compounds, whereas CS and CRO (C. racemosa var. occidentalis) possessed higher total antioxidant, scavenging, and anti-proliferative activities compared to the other selected seaweeds. The study revealed that Caulerpa spp. are a promising functional food ingredient and could be explored as daily dietary supplements.
       
  • Biomass and lipid production of a novel freshwater thermo-tolerant mutant
           strain of Chlorella pyrenoidosa NCIM 2738 in seawater salinity recycled
           medium
    • Abstract: Publication date: December 2018Source: Algal Research, Volume 36Author(s): Preeti Mehta, Rekha Rani, Ravi Gupta, Anshu Shankar Mathur, Suresh Kumar Puri Micro-algae have significant potential for the production of biofuel. It has been previously shown that existing processes of producing micro-algal biofuels are not yet economically viable at commercial scale. Fundamentally, this process will require the implementation of inexpensive harvesting methods and productive algal strains that are tolerant to harsh conditions. The use of freshwater in the large-scale cultivation of microalgae is currently unsustainable; hence, the studies which target the use of seawater medium can reduce the demand of freshwater. Chlorella pyrenoidosa has been extensively studied in freshwater. However, information on the cultivation of C. pyrenoidosa for growth productivity in recycled seawater medium, generated after harvesting through autoflocculation is scarce. In this context, the present study investigates the effect of nutrients sufficient seawater medium following reuse of nutrients exhausted seawater medium on the biochemical composition, biomass and lipid productivities of an in-house developed, thermotolerant strain of C. pyrenoidosa under high temperature (45 °C), outdoor culture conditions. The strain C. pyrenoidosa M18 was found to thrive in seawater medium resulting in increased biomass and lipid productivity. Lipid productivity in seawater medium exceeded 51 mg/Ld−1 which was nearly 2-fold greater than freshwater. Furthermore, the strain was able to grow well and autoflocculate at recycled seawater medium giving biomass and lipid productivities, respectively of 338 mgL−1d−1 and 66 mgL−1d−1. The dry cell weight comprised of 28–32% carbohydrate content when cultivated in recycled seawater medium. Additionally, exposure to high salinity led to an enhanced chlorophyll content as well as increased Fv/Fm ratio. The auto-flocculating property of thermotolerant C. pyrenoidosa M18 strain, in addition to the high biomass and lipid productivities in nutrient exhausted recycled seawater medium, make this microalga an excellent candidate for large-scale outdoor cultivation for biodiesel production.
       
  • Microalgae as a source of vitamin K1
    • Abstract: Publication date: December 2018Source: Algal Research, Volume 36Author(s): Thomas D.C. Tarento, Dale D. McClure, Emily Vasiljevski, Aaron Schindeler, Fariba Dehghani, John M. Kavanagh Vitamin K1 has recently been identified as a potentially important nutrient for prevention of chronic diseases, especially those associated with aging, like osteoporosis and cardiovascular disease. Currently the majority of Vitamin K1 is produced via chemical synthesis; the aim of this work is to examine the potential to produce Vitamin K1 using microalgae. Biological synthesis produces only the active E-isomer, whereas chemical synthesis produces 10–20% of the inactive Z-isomer. Biosynthesis also utilises mild operating conditions, sustainable production methods, and has the potential to simultaneously produce other beneficial compounds. Seven different species of microalgae were screened; the cyanobacterium Anabaena cylindrica was identified as the richest source of vitamin K1. Concentrations were of the order 200 μg g−1 on a dry-weight basis, which is around six times higher than rich dietary sources such as spinach and parsley; one gram of the algae provides approximately three times the daily adult intake for Vitamin K1. By optimizing the growth conditions (lighting and medium), the productivity was increased fourfold to 22 μg L−1 d−1. Analysis of the nutritional properties of the biomass revealed that it contained high levels of protein (69% (w/w)) and Vitamin B12 (1.5 μg g−1), in addition to the high concentration of phylloquinone. An animal study was performed to evaluate the potential toxicity of the biomass; however, no evidence of acute toxicity was observed even at relatively high addition rates (15% (w/w)). These results support the use of microalgae, specifically A. cylindrica, as a source of phylloquinone.Graphical abstractUnlabelled Image
       
  • Production of protein-rich extracts from disrupted microalgae cells:
           Impact of solvent treatment and lyophilization
    • Abstract: Publication date: December 2018Source: Algal Research, Volume 36Author(s): Lutz Grossmann, Sandra Ebert, Jörg Hinrichs, Jochen Weiss This study investigated the preparation of protein-rich extracts from different microalgae by purification and minimal processing approaches (less-refinement) by studying separately the effects of (i) (nonaqueous) solvent-precipitation, (ii) lyophilization, and (iii) (nonaqueous) solvent-washing of lyophilized fractions. Cells were disrupted by high pressure homogenization (180 MPa, 25 °C) and increasing number of passes. Cells were resistant to cell disruption in following order: Phaeodactylum tricornutum 
       
  • The effect of thiamine on the growth and fatty acid content of
           Aurantiochytrium sp
    • Abstract: Publication date: December 2018Source: Algal Research, Volume 36Author(s): Narumi Tani, Kohei Yoneda, Iwane Suzuki Aurantiochytrium sp. is a heterotrophic microorganism that accumulates high amounts of fatty acids (FAs), including odd-chain FAs and an essential FA, docosahexaenoic acid (DHA). Since complex nutrient sources such as tryptone and yeast extract are conventionally utilized in the growth medium for Aurantiochytrium, it is difficult to investigate which individual vitamins affect growth and FA production. Thus, in the present study, we simplified the nitrogen source and defined the vitamins required for Aurantiochytrium sp. cultivation. Glutamate was found to be the most effective simple nitrogen source in cultivation media and thiamine (vitamin B1) was identified as a unique essential vitamin for this organism. Media supplemented with thiamine, as the only member of the vitamin B complex added, allowed for propagation of four strains of Aurantiochytrium. The ratio of odd-chain FAs significantly decreased in the medium containing glucose, glutamate, and thiamine when compared with the conventional medium containing glucose, tryptone, and yeast extract. This is likely caused by a decreased availability of branched-chain amino acids. Under thiamine starvation, FA content per dry cell weight gradually decreased throughout cultivation, and the specific activity of pyruvate dehydrogenase (PDH), a thiamine-dependent enzyme, was severely repressed. These results indicate that when thiamine is absent, the cells compensate some amount of acetyl-CoA through β-oxidation of FAs in vivo, instead of from the reaction by pyruvate, as occurs under normal growth conditions. Providing experimental evidence that the activity of vitamin-dependent enzymes affects biosynthesis of FAs is critical to a better understanding of the effect of vitamin supplementation in Aurantiochytrium sp. media. In the present study, we demonstrated the close relationship between PDH activity, FA content and the importance of thiamine supplementation in the culture medium in Aurantiochytrium sp.
       
  • Reactive oxygen species-mediated caspase-3 pathway involved in cell
           apoptosis of Karenia mikimotoi induced by linoleic acid
    • Abstract: Publication date: December 2018Source: Algal Research, Volume 36Author(s): Meiaoxue Han, Renjun Wang, Ning Ding, Xiuxia Liu, Ningning Zheng, Baoyan Fu, Li Sun, Peike Gao Linoleic acid (LA) secreted by macroalgae has been shown to inhibit harmful algal blooming Karenia mikimotoi. In this study, we investigated the effects of LA on cell proliferation and apoptosis of K. mikimotoi. The results indicated that LA (>500 μg/L) could significantly inhibit the algal proliferation, with the cell cycle blocked at the G2 phase and a clear decrease of photosynthetic pigments. Intracellular reactive oxygen species (ROS) level, malondialdehyde (MDA) content and the activities of antioxidant enzymes (superoxide dismutase (SOD) and catalase (CAT)) were obviously elevated, indicating that LA induced oxidative stress of K. mikimotoi. Several indicators for cell apoptosis, including DNA degradation, increased caspase-3 protease activity and phosphatidylserine (PTS) externalization, were observed in K. mikimotoi treated by LA. Addition of the ROS scavenger N‑acetyl‑l‑cysteine (NAC) decreased caspase-3 activity, and reduced cell apoptosis. Caspase-3 inhibitor also decreased cell apoptosis rate. Summarily, the results suggest that LA induced ROS overproduction, which further stimulated caspase-3, and then induced cell apoptosis of K. mikimotoi.
       
  • Sargassum angustifolium brown macroalga as a high potential substrate for
           alginate and ethanol production with minimal nutrient requirement
    • Abstract: Publication date: December 2018Source: Algal Research, Volume 36Author(s): Yasaman Ardalan, Mohammadhadi Jazini, Keikhosro Karimi The brown macroalga, Sargassum angustifolium harvested from the Persian Gulf in the summer and winter was exploited within a biorefinery approach for valuable bioproducts and ethanol production. This alga mainly contained alginate (20.9–22.4%), glucan (36.2–43.1%), lignin-like materials (i.e., polyphenols; 11.8–25.8%), and ash (43.8–35.5%). The biomass protein content was highly depended on the harvesting season, where the biomass harvested in summer and winter comprised 11.9% and 19.7% protein, respectively. The alginate was first extracted in the form of sodium alginate. Then, the residual biomass obtained during alginate extraction was used for bioethanol production through the separate hydrolysis and fermentation. The results demonstrated that 44.5 (28.0) to 53.3 (32.5) kg of ethanol and 2.4 × 102 (2.2 × 102) kg of sodium alginate could be obtained from each tone of summer (winter) algal biomass. During the extraction of alginate, a nutrient-rich extract, “macroalgal extract”, was produced. This extract was successful substitute for yeast extract, which was necessary for the ethanolic fermentation. The results revealed the great potential of S. angustifolium for implementation as a source of sodium alginate, a nutrient-rich extract, and bioethanol.
       
  • Independent regulation of the lipid and starch synthesis pathways by
           sulfate metabolites in the green microalga Parachlorella kessleri under
           sulfur starvation conditions
    • Abstract: Publication date: December 2018Source: Algal Research, Volume 36Author(s): Tomokazu Yamazaki, Erika Konosu, Tsuyoshi Takeshita, Aiko Hirata, Shuhei Ota, Yusuke Kazama, Tomoko Abe, Shigeyuki Kawano Microalgae accumulate neutral lipids in oil bodies under sulfur-starvation conditions, and determination of the molecular basis of lipid accumulation under sulfur-starvation conditions will enable improvement of the production of biofuel. We analyzed two l-cysteine dependent mutants (Srp1 and Srp2) of the green alga Parachlorella kessleri. The wild-type cells accumulated lipids and developed oil bodies under sulfate-depleted conditions but not under sulfate-replete conditions. Srp1 and Srp2 showed suppressed proliferation and lipid and starch accumulation under sulfate-replete conditions but accumulated only lipids under sulfate-depleted conditions. Although the suppressed cell proliferation of the mutants was partially complemented in medium containing l-cysteine as a sulfur source, that of the wild type was completely complemented, and lipids did not accumulate in the wild type or the mutants. Our results suggest that the accumulation of lipids in P. kessleri under sulfate-depleted conditions results from a shortage of sulfate metabolites, such as l-cysteine, and that sulfate promotes starch accumulation.
       
  • High-light selection produces a fast-growing Picochlorum celeri
    • Abstract: Publication date: December 2018Source: Algal Research, Volume 36Author(s): Joseph C. Weissman, Maria Likhogrud, Dylan C. Thomas, Wei Fang, Devin A.J. Karns, Jeffrey W. Chung, Robert Nielsen, Matthew C. Posewitz A new species of marine algae Picochlorum celeri was obtained by enriching for fast reproductive rates under constant high irradiance in semi-continuous culture. Several rapidly-growing cell lines were isolated from the enrichment culture by bringing up cultures from single cells in very high light. Therefore, individual cells are very resilient to inhibition by light. This is a prominent characteristic of this P. celeri in all cell lines. Measured oxygen evolution rates were unusually high. One of these lines is able to double in as short as 2.0 h. Doubling times of other cell lines were between 2.4 and 3.5 h. This species is characterized by high pigment content, high absorption cross section, and an antenna size that is very responsive to irradiance becoming very small at high irradiance.
       
  • Impact of seconds to minutes photoperiods on Chlorella vulgaris growth
           rate and chlorophyll a and b content
    • Abstract: Publication date: December 2018Source: Algal Research, Volume 36Author(s): Wendie Levasseur, Behnam Taidi, Robin Lacombe, Patrick Perré, Victor Pozzobon In order to determine the impact of photoperiod duration, Chlorella vulgaris was studied in low cell density batch culture for seven days. Different photoperiod cycles ranging from minutes to seconds intervals were applied and their impact on microalgae cells growth and chlorophyll a and b contents were compared against a reference culture that was continuously illuminated. The selected photoperiods are typical of those due to alternance of dark and light zones along the algae trajectories inside photobioreactors. Throughout this study, all cultures received the same total amount of photons.When photoperiods of minutes duration were applied, the cells grew more slowly (0.052 ± 0.003 h−1) but contained higher average contents of chlorophyll pigments (0.27 ± 0.03 pg⋅cell−1) than those cells grown under continuous illumination (0.062 ± 0.003 h−1 and 0.42 ± 0.08 pg⋅cell−1, respectively). Cultures exposed to photoperiods of seconds duration grew the fastest (0.072 ± 0.002 h−1) with fewer photosynthetic units (0.61 ± 0.08 pg⋅cell−1) than the cells grown with continuous illumination. These results suggest that light harvesting systems have a higher efficiency with photoperiods of duration in the seconds range.
       
  • Biotechnological potential of Neolyngbya (Cyanobacteria), a new marine
           benthic filamentous genus from Brazil
    • Abstract: Publication date: December 2018Source: Algal Research, Volume 36Author(s): Taiara Aguiar Caires, Aaron M.S. da Silva, Viviane M. Vasconcelos, Helen M.J. Affe, Lourdes C. de Souza Neta, Heiter V.M. Boness, Célia L. Sant'Anna, José M.C. Nunes Marine filamentous cyanobacteria are sources of biologically active secondary metabolites with potential biotechnological application. Despite the extension and environmental variety of the Brazilian coast, floristic surveys of filamentous cyanobacteria are scarce. Studies on their biotechnological potential are even more limited. In this work, we sampled Neolyngbya (Oscillatoriaceae) populations along the Brazilian coast and evaluated the antimicrobial, antioxidant, and cytotoxic activities of their organic extracts. We also assessed the strains' genetic potential for production of cyanotoxins. The strains were cultivated in SWBG-11 medium. Extraction of biomass was carried out with methanol, ethanol, and acetic acid. Antimicrobial (against seven bacterial strains and the yeast Candida albicans), antioxidant (DPPH and ABTS radicals), and cytotoxic (brine shrimp) potential were evaluated. PCR reactions were performed to analyze the genetic potential for the production of microcystin, saxitoxin, and cylindrospermopsin. Brazilian marine filamentous cyanobacteria presented relevant antimicrobial capacity. Seven extracts from four Neolyngbya strains inhibited growth of almost all bacteria, while nine extracts from four strains inhibited C. albicans, with a minimum inhibitory concentration (MIC) range from 2.5 to 10.0 mg·mL−1. Methanolic extracts presented the greatest antioxidant potential for both DPPH and ABTS radicals, ranging from 50.0 to 98.3% at a concentration of 10 mg·mL−1. Cytotoxicity assays showed a LC50 ranging from 0.8 to 6.6 mg·mL−1. We detected toxic genotypes in eight of the analyzed strains, in which the most frequent gene clusters were mcyG (microcystin) and cyrJ (cylindrospermopsin). All Neolyngbya strains screened in this study have potential for biotechnological application, which highlights the economical and pharmacological importance of studying this underestimated biodiversity in tropical areas.
       
 
 
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