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  Subjects -> BIOLOGY (Total: 3134 journals)
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BIOTECHNOLOGY (236 journals)                  1 2 | Last

Showing 1 - 200 of 237 Journals sorted alphabetically
3 Biotech     Open Access   (Followers: 8)
Advanced Biomedical Research     Open Access  
Advances in Bioscience and Biotechnology     Open Access   (Followers: 14)
Advances in Genetic Engineering & Biotechnology     Hybrid Journal   (Followers: 8)
African Journal of Biotechnology     Open Access   (Followers: 6)
Algal Research     Partially Free   (Followers: 10)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 64)
American Journal of Bioinformatics Research     Open Access   (Followers: 7)
American Journal of Polymer Science     Open Access   (Followers: 31)
Anadolu University Journal of Science and Technology : C Life Sciences and Biotechnology     Open Access  
Animal Biotechnology     Hybrid Journal   (Followers: 8)
Annales des Sciences Agronomiques     Full-text available via subscription  
Applied Biochemistry and Biotechnology     Hybrid Journal   (Followers: 43)
Applied Bioenergy     Open Access  
Applied Biosafety     Hybrid Journal  
Applied Food Biotechnology     Open Access   (Followers: 3)
Applied Microbiology and Biotechnology     Hybrid Journal   (Followers: 63)
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: 8)
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)
Bio-Algorithms and Med-Systems     Hybrid Journal   (Followers: 2)
Bio-Research     Full-text available via subscription   (Followers: 2)
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  
Biofuels     Hybrid Journal   (Followers: 11)
Biofuels Engineering     Open Access   (Followers: 1)
Biological & Pharmaceutical Bulletin     Full-text available via subscription   (Followers: 4)
Biological Cybernetics     Hybrid Journal   (Followers: 10)
Biomarkers and Genomic Medicine     Open Access   (Followers: 3)
Biomarkers in Drug Development     Partially Free   (Followers: 1)
Biomaterials Research     Open Access   (Followers: 4)
BioMed Research International     Open Access   (Followers: 4)
Biomédica     Open Access  
Biomedical and Biotechnology Research Journal     Open Access  
Biomedical Engineering Research     Open Access   (Followers: 6)
Biomedical glasses     Open Access  
Biomedical Reports     Full-text available via subscription  
BioMedicine     Open Access  
Biomedika     Open Access  
Bioprinting     Hybrid Journal   (Followers: 1)
Bioresource Technology Reports     Hybrid Journal   (Followers: 1)
Bioscience, Biotechnology, and Biochemistry     Hybrid Journal   (Followers: 21)
Biosimilars     Open Access   (Followers: 1)
Biosurface and Biotribology     Open Access  
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 2)
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: 5)
Biotechnology & Biotechnological Equipment     Open Access   (Followers: 4)
Biotechnology Advances     Hybrid Journal   (Followers: 33)
Biotechnology and Applied Biochemistry     Hybrid Journal   (Followers: 44)
Biotechnology and Bioengineering     Hybrid Journal   (Followers: 155)
Biotechnology and Bioprocess Engineering     Hybrid Journal   (Followers: 5)
Biotechnology and Genetic Engineering Reviews     Hybrid Journal   (Followers: 13)
Biotechnology and Health Sciences     Open Access   (Followers: 1)
Biotechnology and Molecular Biology Reviews     Open Access   (Followers: 1)
Biotechnology Annual Review     Full-text available via subscription   (Followers: 5)
Biotechnology for Biofuels     Open Access   (Followers: 10)
Biotechnology Frontier     Open Access   (Followers: 2)
Biotechnology Journal     Hybrid Journal   (Followers: 16)
Biotechnology Law Report     Hybrid Journal   (Followers: 4)
Biotechnology Letters     Hybrid Journal   (Followers: 34)
Biotechnology Progress     Hybrid Journal   (Followers: 39)
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  
Biotribology     Hybrid Journal   (Followers: 1)
BMC Biotechnology     Open Access   (Followers: 16)
Cell Biology and Development     Open Access  
Chinese Journal of Agricultural Biotechnology     Full-text available via subscription   (Followers: 4)
Communications in Mathematical Biology and Neuroscience     Open Access  
Computational and Structural Biotechnology Journal     Open Access   (Followers: 2)
Computer Methods and Programs in Biomedicine     Hybrid Journal   (Followers: 8)
Contributions to Tobacco Research     Open Access   (Followers: 2)
Copernican Letters     Open Access   (Followers: 1)
Critical Reviews in Biotechnology     Hybrid Journal   (Followers: 20)
Crop Breeding and Applied Biotechnology     Open Access   (Followers: 3)
Current Bionanotechnology     Hybrid Journal  
Current Biotechnology     Hybrid Journal   (Followers: 4)
Current Opinion in Biomedical Engineering     Hybrid Journal   (Followers: 1)
Current Opinion in Biotechnology     Hybrid Journal   (Followers: 56)
Current Pharmaceutical Biotechnology     Hybrid Journal   (Followers: 9)
Current Research in Bioinformatics     Open Access   (Followers: 12)
Current Trends in Biotechnology and Chemical Research     Open Access   (Followers: 3)
Current trends in Biotechnology and Pharmacy     Open Access   (Followers: 8)
EBioMedicine     Open Access  
Electronic Journal of Biotechnology     Open Access  
Entomologia Generalis     Full-text available via subscription  
Environmental Science : Processes & Impacts     Full-text available via subscription   (Followers: 4)
Experimental Biology and Medicine     Hybrid Journal   (Followers: 3)
Folia Medica Indonesiana     Open Access  
Food Bioscience     Hybrid Journal  
Food Biotechnology     Hybrid Journal   (Followers: 9)
Food Science and Biotechnology     Hybrid Journal   (Followers: 8)
Frontiers in Bioengineering and Biotechnology     Open Access   (Followers: 6)
Frontiers in Systems Biology     Open Access   (Followers: 2)
Fungal Biology and Biotechnology     Open Access   (Followers: 2)
GM Crops and Food: Biotechnology in Agriculture and the Food Chain     Full-text available via subscription   (Followers: 1)
GSTF Journal of BioSciences     Open Access  
HAYATI Journal of Biosciences     Open Access  
Horticulture, Environment, and Biotechnology     Hybrid Journal   (Followers: 11)
IEEE Transactions on Molecular, Biological and Multi-Scale Communications     Hybrid Journal   (Followers: 1)
IET Nanobiotechnology     Hybrid Journal   (Followers: 2)
IIOAB Letters     Open Access  
IN VIVO     Full-text available via subscription   (Followers: 4)
Indian Journal of Biotechnology (IJBT)     Open Access   (Followers: 2)
Indonesia Journal of Biomedical Science     Open Access   (Followers: 2)
Indonesian Journal of Biotechnology     Open Access   (Followers: 1)
Industrial Biotechnology     Hybrid Journal   (Followers: 18)
International Biomechanics     Open Access  
International Journal of Bioinformatics Research and Applications     Hybrid Journal   (Followers: 13)
International Journal of Biomechatronics and Biomedical Robotics     Hybrid Journal   (Followers: 4)
International Journal of Biomedical Research     Open Access   (Followers: 2)
International Journal of Biotechnology     Hybrid Journal   (Followers: 5)
International Journal of Biotechnology and Molecular Biology Research     Open Access   (Followers: 2)
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)
Journal of Biometrics & Biostatistics     Open Access   (Followers: 3)
Journal of Bioterrorism & Biodefense     Open Access   (Followers: 6)
Journal of Petroleum & Environmental Biotechnology     Open Access   (Followers: 1)
Journal of Advanced Therapies and Medical Innovation Sciences     Open Access  
Journal of Advances in Biotechnology     Open Access   (Followers: 5)
Journal Of Agrobiotechnology     Open Access  
Journal of Analytical & Bioanalytical Techniques     Open Access   (Followers: 7)
Journal of Animal Science and Biotechnology     Open Access   (Followers: 4)
Journal of Applied Biomedicine     Open Access   (Followers: 2)
Journal of Applied Biotechnology     Open Access   (Followers: 2)
Journal of Applied Biotechnology Reports     Open Access   (Followers: 2)
Journal of Applied Mathematics & Bioinformatics     Open Access   (Followers: 5)
Journal of Biologically Active Products from Nature     Hybrid Journal   (Followers: 1)
Journal of Biomaterials and Nanobiotechnology     Open Access   (Followers: 6)
Journal of Biomedical Photonics & Engineering     Open Access  
Journal of Biomedical Practitioners     Open Access  
Journal of Bioprocess Engineering and Biorefinery     Full-text available via subscription  
Journal of Bioprocessing & Biotechniques     Open Access  
Journal of Biosecurity, Biosafety and Biodefense Law     Hybrid Journal   (Followers: 3)
Journal of Biotechnology     Hybrid Journal   (Followers: 68)
Journal of Biotechnology and Strategic Health Research     Open Access  
Journal of Chemical and Biological Interfaces     Full-text available via subscription   (Followers: 1)
Journal of Chemical Technology & Biotechnology     Hybrid Journal   (Followers: 9)
Journal of Chitin and Chitosan Science     Full-text available via subscription  
Journal of Colloid Science and Biotechnology     Full-text available via subscription  
Journal of Commercial Biotechnology     Full-text available via subscription   (Followers: 6)
Journal of Crop Science and Biotechnology     Hybrid Journal   (Followers: 3)
Journal of Essential Oil Research     Hybrid Journal   (Followers: 2)
Journal of Experimental Biology     Full-text available via subscription   (Followers: 24)
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: 16)
Journal of Integrative Bioinformatics     Open Access  
Journal of International Biotechnology Law     Hybrid Journal   (Followers: 3)
Journal of Medical Imaging and Health Informatics     Full-text available via subscription  
Journal of Molecular Biology and Biotechnology     Open Access  
Journal of Molecular Microbiology and Biotechnology     Full-text available via subscription   (Followers: 11)
Journal of Nano Education     Full-text available via subscription  
Journal of Nanobiotechnology     Open Access   (Followers: 4)
Journal of Nanofluids     Full-text available via subscription   (Followers: 1)
Journal of Organic and Biomolecular Simulations     Open Access  
Journal of Plant Biochemistry and Biotechnology     Hybrid Journal   (Followers: 4)
Journal of Science and Applications : Biomedicine     Open Access  
Journal of the Mechanical Behavior of Biomedical Materials     Hybrid Journal   (Followers: 11)
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)
Messenger     Full-text available via subscription  
Metabolic Engineering Communications     Open Access   (Followers: 4)
Metalloproteinases In Medicine     Open Access  
Microalgae Biotechnology     Open Access   (Followers: 2)
Microbial Biotechnology     Open Access   (Followers: 9)
MicroMedicine     Open Access   (Followers: 3)
Molecular and Cellular Biomedical Sciences     Open Access  
Molecular Biotechnology     Hybrid Journal   (Followers: 13)
Molecular Genetics and Metabolism Reports     Open Access   (Followers: 3)
Nanobiomedicine     Open Access  
Nanobiotechnology     Hybrid Journal   (Followers: 2)
Nanomaterials and Nanotechnology     Open Access  
Nanomaterials and Tissue Regeneration     Open Access  
Nanomedicine and Nanobiology     Full-text available via subscription  
Nanomedicine Research Journal     Open Access  
Nanotechnology Reviews     Hybrid Journal   (Followers: 5)
Nature Biotechnology     Full-text available via subscription   (Followers: 535)

        1 2 | Last

Journal Cover Algal Research
  [SJR: 2.05]   [H-I: 20]   [10 followers]  Follow
    
   Partially Free Journal Partially Free Journal
   ISSN (Online) 2211-9264
   Published by Elsevier Homepage  [3162 journals]
  • Indigenous microalga Parachlorella sp. JD-076 as a potential source for
           lutein production: Optimization of lutein productivity via regulation of
           light intensity and carbon source
    • Authors: Jina Heo; Dong-Sik Shin; Kichul Cho; Dae-Hyun Cho; Yong Jae Lee; Hee-Sik Kim
      Pages: 1 - 7
      Abstract: Publication date: July 2018
      Source:Algal Research, Volume 33
      Author(s): Jina Heo, Dong-Sik Shin, Kichul Cho, Dae-Hyun Cho, Yong Jae Lee, Hee-Sik Kim
      Lutein has attracted attention because of its beneficial roles, including alleviating cardiovascular diseases. We compared lutein production of diverse indigenous algal candidates, and selected Parachlorella sp. JD-076 as a lutein producer. The strain was cultivated under different types of photo-bioreactors (PBRs). Maximal growth was obtained from the tubular type with 2.7-fold higher dry cell weight (DCW) than in the cylindrical type. To optimize lutein production, Parachlorella sp. was exposed to various levels of illumination (100–1000 μmol m−2 s−1) and combinations of glucose and CO2 in the tubular-type PBR. High-light intensity efficiently increased DCW and lutein productivity in an intensity-dependent manner, and 5% CO2 resulted in the maximum biomass and lutein productivity compared to that of other conditions, with 2.1 g L−1 day−1 and 25 mg L−1 day−1, respectively. We speculated that the strain Parachlorella sp. JD-076 will provide a cost-effective lutein bioprocess via regulation of illumination and CO2 supply.

      PubDate: 2018-05-29T04:18:03Z
      DOI: 10.1016/j.algal.2018.04.029
      Issue No: Vol. 33 (2018)
       
  • Integrated analyses of transcriptome, proteome and fatty acid profilings
           of the oleaginous microalga Auxenochlorella protothecoides UTEX 2341
           reveal differential reprogramming of fatty acid metabolism in response to
           low and high temperatures
    • Authors: GuanLan Xing; HongLi Yuan; JinShui Yang; JinYu Li; QuanXiu Gao; WeiLin Li; EnTao Wang
      Pages: 16 - 27
      Abstract: Publication date: July 2018
      Source:Algal Research, Volume 33
      Author(s): GuanLan Xing, HongLi Yuan, JinShui Yang, JinYu Li, QuanXiu Gao, WeiLin Li, EnTao Wang
      Temperature is one of the critical environmental factors that influence microalgal growth, lipid content and fatty acid (FA) composition. However, the molecular mechanism underlying regulations of FA metabolism under low and high temperature stress in oleaginous microalgae remains unclear. In this study, integrated analyses of transcriptome, proteome and fatty acid profilings were performed for the first time in Auxenochlorella protothecoides UTEX 2341. Under low and high temperature (LT and HT) stress, a total of 5565 and 4757 genes, and 1311 and 728 proteins were differentially expressed respectively. 65 actively expressed genes and 61 proteins involved in FA metabolism were identified. A strong positive correlation between the genes' transcript and protein levels existed in FA metabolism (r = 0.80, p-value < 0.01⁎⁎, LT vs NT; r = 0.61, p-value < 0.01⁎⁎, HT vs NT). Two models were proposed to reveal differential reprogramming of FA metabolism induced by low and high temperatures. Low temperature promoted chloroplast FA biosynthesis by enhancing the expression of the plastidial acetyl-CoA carboxylase (ACCase) and type-II fatty acid synthase. High temperature activated FA biosynthesis, including polyunsaturated and very-long-chain FAs in the cytosol and endoplasmic reticulum (ER) by increasing the expression of the cytosolic ACCase, type-I polyketide synthase and components of the ER-located elongase complex. The enhanced expression of the plastid-located pyruvate dehydrogenase complex (PDHC) and the suppressed FA β-oxidation also highly contributed to lipid accumulation. The biosynthesis of ω-3 fatty acid was closely related to microalgae's temperature adaptability. These results indicated that the reprogramming of FA metabolism was implicated in microalgae response to temperature stress. The above findings not only had important implications for the screening and genetic engineering of algae and plants to improve their lipid productions, but also provided novel insight into the adaptive mechanism to temperature stress.
      Graphical abstract image

      PubDate: 2018-05-29T04:18:03Z
      DOI: 10.1016/j.algal.2018.04.028
      Issue No: Vol. 33 (2018)
       
  • Choricystis minor var. minor lipids: Extraction using conventional and
           pressurized solvents and assessment of their potential to produce fatty
           acid methyl esters
    • Authors: Aline Andreza da Cruz Lima; Daiane Szczerbowski; Arion Zandoná Filho; Roberto Bianchini Derner; Marcos Lúcio Corazza; Luiz Pereira Ramos
      Pages: 28 - 35
      Abstract: Publication date: July 2018
      Source:Algal Research, Volume 33
      Author(s): Aline Andreza da Cruz Lima, Daiane Szczerbowski, Arion Zandoná Filho, Roberto Bianchini Derner, Marcos Lúcio Corazza, Luiz Pereira Ramos
      Microalgae are potential raw materials for biofuel applications. In this work, microbial lipids from Choricystis minor var. minor were extracted with conventional solvents in a Soxhlet apparatus and with compressed fluids with or without the use of a co-solvent (ethanol or hexane). Also, the total achievable yield of fatty acid methyl esters (FAME) was determined in both unextracted microalga, extraction residue and extracted lipids. Ethanol was the best solvent for conventional extraction but hexane was more selective for saponifiable lipids. Compressed propane was better than supercritical carbon dioxide (scCO2) for the extraction of microbial lipids and the use of ethanol as co-solvent improved both extraction rates and yields. The best FAME yield was achieved with scCO2 plus ethanol at 80 °C and 150 bar (FAME yield of 16.7 g 100 g−1 dry biomass for a mass extraction yield of 31.6%). Hexane was not advantageous as an extraction co-solvent.
      Graphical abstract image

      PubDate: 2018-05-29T04:18:03Z
      DOI: 10.1016/j.algal.2018.04.017
      Issue No: Vol. 33 (2018)
       
  • Production method and cost of commercial-scale offshore cultivation of
           kelp in the Faroe Islands using multiple partial harvesting
    • Authors: Urd Grandorf Bak; Agnes Mols-Mortensen; Olavur Gregersen
      Pages: 36 - 47
      Abstract: Publication date: July 2018
      Source:Algal Research, Volume 33
      Author(s): Urd Grandorf Bak, Agnes Mols-Mortensen, Olavur Gregersen
      The current work aimed to develop a cultivation method for macroalgae that can be applicable and economically profitable in the Atlantic Ocean. An offshore long-line macroalgal cultivation rig was designed by Ocean Rainforest Sp/f, tested in the Faroe Islands from 2010, and found suitable for cultivation in exposed and deep-water locations (water depth > 50 m). The economic risk related to lost cultivation structures was hereafter considered to be low. Saccharina latissima and Alaria esculenta were cultivated in commercial scale (5 km of growth lines). A high cost of seeding material and cost of deployment was reduced by testing multiple partial harvesting. Four non-destructive harvests were carried out in a two-year growth period without re-seeding of lines. In total, 3.2 t dry weight (dw) biomass was harvested and sold to customers within the food and cosmetic industries. The productivity was 1437.5 kg dw ha−1 yr−1 (including handling space). The 10-meter vertical growth lines had an average yield of 0.29 kg dw m−1 per harvest and four partial harvests were made over a 2-year period. An economic analysis showing the cost structure of important aspects of offshore macroalgae cultivation was conducted. The total cost per kg dw of cultivated S. latissima decreased when the number of possible harvests without re-seeding was increased (from € 36.73 to € 9.27). This work has demonstrated that large-scale kelp cultivation is possible using multiple partial harvesting in the Faroe Islands, and highlighted the need for further innovation to lower the cost per unit macroalgal produced.

      PubDate: 2018-05-29T04:18:03Z
      DOI: 10.1016/j.algal.2018.05.001
      Issue No: Vol. 33 (2018)
       
  • Effects of dietary Nannochloropsis salina on the nutritional performance
           and fatty acid profile of Nile tilapia, Oreochromis niloticus
    • Authors: Oluyemi K. Gbadamosi; Ingrid Lupatsch
      Pages: 48 - 54
      Abstract: Publication date: July 2018
      Source:Algal Research, Volume 33
      Author(s): Oluyemi K. Gbadamosi, Ingrid Lupatsch
      This study assessed the effects of dietary Nannochloropsis salina on the nutritional performance and fatty acid profile of Nile tilapia, Oreochromis niloticus. Three isonitrogenous and isocaloric diets were formulated to contain 35% crude protein and 13% lipid. In the first diet, protein and lipid was solely from fish meal and fish oil, the second diet was based on soybean meal and soybean oil and the third diet was based on Nannochloropsis salina meal. Three replicate groups of fish (initial weight, 12.70 ± 0.03 g) were used for each diet. Fish were fed manually to apparent satiation for 36 days. At the end of the feeding trial, fish fed the Nannochloropsis diet had similar weight gain but significantly (P < 0.05) better feed conversion ratio than those fed the soybean diet. Moreover, significantly higher protein retention efficiencies (28.86%) were found in fish fed Nannochloropsis diet than those fed the soybean meal diet (26.84%). The fatty acid profile of fish body was influenced by the fatty acid composition of the diets. There was no difference between the total n-3 polyunsaturated and n-3/n-6 fatty acid ratio of fish fed the fish meal and Nannochloropsis diet. However, both n-3 polyunsaturated and n-3/n-6 fatty acid ratio of fish were higher compared to those recorded in fish fed the soybean meal diet. Generally, this study showed that O. niloticus fed N. salina based diet was able to have comparably good nutritional performance with fish meal and soybean meal. Furthermore, data on the fatty acid profile showed that N. salina could replace fish and soybean oil in the diet of Nile tilapia.

      PubDate: 2018-05-29T04:18:03Z
      DOI: 10.1016/j.algal.2018.04.030
      Issue No: Vol. 33 (2018)
       
  • Improved liquid foam-bed photobioreactor design for microalgae cultivation
    • Authors: Agnes Janoska; Robin Barten; Sam de Nooy; Piotr van Rijssel; René H. Wijffels; Marcel Janssen
      Pages: 55 - 70
      Abstract: Publication date: July 2018
      Source:Algal Research, Volume 33
      Author(s): Agnes Janoska, Robin Barten, Sam de Nooy, Piotr van Rijssel, René H. Wijffels, Marcel Janssen
      The liquid foam-bed photobioreactor is a recently developed photobioreactor concept that allows for cost reduction in microalgae cultivation. Long term operation was not yet achieved, due to degradation of the surfactant. In this study, Pluronic F68 was applied for foam stabilization. In order to compensate for the low algae partitioning to Pluronic F68 stabilized foam, liquid recirculation was introduced into the reactor design. The microalgal suspension was continuously pumped from the bottom of the reactor to the top of the foam column where it was allowed to drain down again through the foam. This new design allowed increased mixing and, thereby, a homogenous algae distribution within the reactor. The volumetric mass transfer coefficient for CO2 in the foam-bed was 0.14 s−1, revealing that the gas transfer rate is an order of magnitude higher compared to bubble column reactors. This characteristic, together with a very high gas residence time, allows for a dramatic reduction in gas flow rate and a high carbon dioxide utilization efficiency. Long-term cultivation (>500 h) of Chlorella sp. was achieved in a stable foam-bed. The areal productivity of the foam-bed photobioreactor was 57 g m−2 d−1, which is slightly lower than maximally achieved in flat panels under similar conditions. This is possibly related to substantial light scattering taking place in the foam leading to a steeper light gradient and increased reflection. The reactor dilution rate and the liquid recirculation rate were not optimized during our experiments and there is room for further improvement. During continuous reactor operation, biomass densities of >20 g L−1 could be maintained. This biomass density is a factor of 10 higher compared to traditional, liquid phase photobioreactors, thereby, contributing to reduced energy requirements for microalgae harvesting.

      PubDate: 2018-05-29T04:18:03Z
      DOI: 10.1016/j.algal.2018.04.025
      Issue No: Vol. 33 (2018)
       
  • Repeated mutagenic effects of 60Co-γ irradiation coupled with
           high-throughput screening improves lipid accumulation in mutant strains of
           the microalgae Chlorella pyrenoidosa as a feedstock for bioenergy
    • Authors: Weiliang Wang; Tingting Wei; Jianhua Fan; Jun Yi; Yuanguang Li; Minxi Wan; Jun Wang; Wenmin Bai
      Pages: 71 - 77
      Abstract: Publication date: July 2018
      Source:Algal Research, Volume 33
      Author(s): Weiliang Wang, Tingting Wei, Jianhua Fan, Jun Yi, Yuanguang Li, Minxi Wan, Jun Wang, Wenmin Bai
      In this study, the repeated mutagenic effects of 60Co-γ irradiation combined with an optimized high-throughput screening method was applied to Chlorella pyrenoidosa to improve lipid productivity and characteristics for biodiesel. Two mutants of Chlorella pyrenoidosa, CP-232 and CP-269, were obtained. The lipid contents obtained from CP-232 and CP-269 were respectively increased by 20.8% and 20% under heterotrophic seed-photoautotrophic culture (HS-PC) model, and by 15% and 20.8% under photoautotrophic seed-photoautotrophic culture (PS-PC) model compared with the wild type strain in 1 L bubble column reactor. In addition, 60Co-γ irradiation mutagenesis increased the proportion of saturated fatty acids in lipids accumulated in CP-232 and CP-269 compared to the wild type strain. In 3 L and 15 L bioreactor scale-up, lipid productivity was equally significantly increased in both CP-232 and CP-269 mutant strains. Our findings indicated that 60Co-γ irradiation mutagenesis improves the accumulation of lipids with potential for industrial biodiesel production in mutant C. pyrenoidosa strains.

      PubDate: 2018-05-29T04:18:03Z
      DOI: 10.1016/j.algal.2018.04.022
      Issue No: Vol. 33 (2018)
       
  • Rheological properties of microalgae slurry under subcritical conditions
           for hydrothermal hydrolysis systems
    • Authors: Hong Zhang; Qiang Liao; Qian Fu; Hao Chen; Yun Huang; Ao Xia; Xun Zhu; Alissara Reungsang; Zhidan Liu; Jun Li
      Pages: 78 - 83
      Abstract: Publication date: July 2018
      Source:Algal Research, Volume 33
      Author(s): Hong Zhang, Qiang Liao, Qian Fu, Hao Chen, Yun Huang, Ao Xia, Xun Zhu, Alissara Reungsang, Zhidan Liu, Jun Li
      Hydrothermal hydrolysis is an effective pretreatment for biogas production from microalgae via fermentation. The rheological properties of microalgae slurry under subcritical conditions significantly affect the heat transfer performance and hence the energy requirement of hydrothermal reactors. In this study, we investigated the rheological properties of microalgae slurry under subcritical conditions (2 MPa, 100–200 °C). For the first time, we found that the apparent viscosity of microalgae slurry under subcritical conditions first drastically increased, and then gradually decreased with the increasing temperature, which is quite different with the variation trend at low temperatures (<70 °C). In addition, the temperatures corresponding to the maximum apparent viscosities were different at different shear rates, which was probably due to the combined effects of starch gelatinization and protein denaturation at high temperatures. Finally, the relationship of the apparent viscosity of microalgae slurry with the temperature and shear rate was obtained.

      PubDate: 2018-05-29T04:18:03Z
      DOI: 10.1016/j.algal.2018.04.026
      Issue No: Vol. 33 (2018)
       
  • Supplemental microalgal astaxanthin produced coordinated changes in
           intrinsic antioxidant systems of layer hens exposed to heat stress
    • Authors: A.D. Magnuson; T. Sun; R. Yin; G. Liu; S. Tolba; S. Shinde; X.G. Lei
      Pages: 84 - 90
      Abstract: Publication date: July 2018
      Source:Algal Research, Volume 33
      Author(s): A.D. Magnuson, T. Sun, R. Yin, G. Liu, S. Tolba, S. Shinde, X.G. Lei
      Astaxanthin is a well-known antioxidant phytochemical that has limited bioavailability to humans. The present study was conducted to determine if microalgal astaxanthin was bioavailable to layer hens and affected antioxidant status of their tissues and eggs. A total of 50 White Leghorn Shavers (21-wk old) were divided into 5 groups (n = 10/group), caged individually in an environmentally-controlled room, and fed a corn-soybean meal basal diet supplemented with microalgal (Haematococcus pluvialis) astaxanthin (Heliae, Gibert, AZ) at 0, 10, 20, 40, and 80 mg/kg for 6 wk. Heat stress was induced during weeks 4–6 when the ambient temperature was raised 3 °C above the optimal temperature. Supplemental microalgal astaxanthin resulted in dose-dependent enrichments (P < 0.05) of astaxanthin and total carotenoids in the plasma and egg yolk of hens. The maximal concentrations of astaxanthin reached 4.1 μg/mL, 5.8 mg/kg, and 36 mg/kg, whereas those of total carotenoids reached 7.0 μg/mL, 75 mg/kg, and 114 mg/kg (on fresh tissue basis), respectively, in the plasma, liver, and egg yolk of hens. The oxygen radical absorbance capacity was also enhanced (P < 0.05) in a dose-dependent fashion in the liver and egg yolk of hens. Meanwhile, total glutathione concentration and activities of glutathione peroxidase and glutathione-S transferase in the liver of hens were decreased (P < 0.05) by the supplemental astaxanthin, compared with the control. Egg yolk color was changed (P < 0.05, more red) by the supplementation, and total PUFA concentration increased (P < 0.05) in the highest astaxanthin treatment group. In conclusion, supplemental dietary microalgal astaxanthin seemed to be highly bioavailable to be deposited in the plasma, liver, and eggs of hens, independent of heat stress, and resulted in coordinated changes in the intrinsic antioxidant systems.

      PubDate: 2018-05-29T04:18:03Z
      DOI: 10.1016/j.algal.2018.04.031
      Issue No: Vol. 33 (2018)
       
  • Fed-batch mixotrophic cultivation of Chlamydomonas reinhardtii for
           high-density cultures
    • Authors: Francis J. Fields; Joseph T. Ostrand; Stephen P. Mayfield
      Pages: 109 - 117
      Abstract: Publication date: July 2018
      Source:Algal Research, Volume 33
      Author(s): Francis J. Fields, Joseph T. Ostrand, Stephen P. Mayfield
      The green algae Chlamydomonas reinhardtii is a model organism that has been proposed as a potential production platform for high-value recombinant products, but to date, there has been little development of a commercially viable cultivation process. Here we demonstrate a novel mixotrophic fed-batch cultivation strategy in which average biomass density, productivity, and total amount of recombinant GFP significantly increases. Systematic feeding of acetic acid and nutrients into a bioreactor resulted in culture densities increasing from an initial 0.45 ± 0.03 to 23.69 ± 0.5 g L−1 AFDW after 168 h at an average productivity of 181.01 ± 8.8 mg L−1 h−1, a 10-fold increase in comparison to traditional batch cultures. GFP expression was low under both conditions, but fed-batch cultivation resulted in a 2.5-fold increase in total GFP upon culture termination. The effect of fed-batch cultivation on lipid composition and primary metabolites was investigated and elevated levels of the osmoregulatory molecules proline and glycerol were found, suggesting that salt accumulation may have increased over time in fed-batch cultures and eventually limited growth.

      PubDate: 2018-05-29T04:18:03Z
      DOI: 10.1016/j.algal.2018.05.006
      Issue No: Vol. 33 (2018)
       
  • Pilot scale dewatering of Chlorella sorokiniana and Dunaliella tertiolecta
           by sedimentation followed by dynamic filtration
    • Authors: M. Hapońska; E. Clavero; J. Salvadó; X. Farriol; C. Torras
      Pages: 118 - 124
      Abstract: Publication date: July 2018
      Source:Algal Research, Volume 33
      Author(s): M. Hapońska, E. Clavero, J. Salvadó, X. Farriol, C. Torras
      The present work focuses on the application of pH-induced sedimentation combined with dynamic filtration for microalgae culture concentration at pilot scale. Concentrations were performed on cultures of two microalgae species: Dunaliella tertiolecta and Chlorella sorokiniana. The objective of the combined process was to reduce microalgae dewatering costs. It is true that sedimentation reduces operation costs considerably, but the results of membrane filtration offer a total rejection and high final concentrations, at even a cheaper cost than centrifugation. When using the two technologies in series, high concentration factors with values up to 207.4 for Dunaliella tertiolecta and 245.3 for Chlorella sorokiniana were achieved. The final concentration of Dunaliella tertiolecta was 184.58 g L−1 with 81.5% of water content in the sludge. The concentrations obtained were high enough to dispense with further operations for the sludge to be ready for a cell disruption step using steam explosion. Analytic techniques used were dry weight and optical density. For the filtration, experiments were performed using both commercially available and self-prepared membranes, manufactured from Acrylonitrile Butadiene Styrene: a novel polymer in membrane technology, selected to reduce costs. Each of them could perform in a similar way to commercial membranes in a pilot scale high-shear stress membrane module.
      Graphical abstract image

      PubDate: 2018-05-29T04:18:03Z
      DOI: 10.1016/j.algal.2018.05.007
      Issue No: Vol. 33 (2018)
       
  • Effect of nitrogen addition on lipid productivity of nitrogen starved
           Nannochloropsis gaditana
    • Authors: Jorijn H. Janssen; Jens Kastenhofer; Jacob A. de Hoop; Packo P. Lamers; René H. Wijffels; Maria J. Barbosa
      Pages: 125 - 132
      Abstract: Publication date: July 2018
      Source:Algal Research, Volume 33
      Author(s): Jorijn H. Janssen, Jens Kastenhofer, Jacob A. de Hoop, Packo P. Lamers, René H. Wijffels, Maria J. Barbosa
      Microalgae are a sustainable source of lipids. A commonly used strategy for lipid accumulation in microalgae is a two-step batch cultivation, with a growth phase followed by a nitrogen starvation phase. A problem with this process is the decrease in photosynthetic efficiency during the nitrogen starvation phase, which leads to low lipid productivities. In this research, a new process strategy was studied with the aim to improve lipid productivity of the microalgae Nannochloropsis gaditana. The nitrogen concentrations were chosen to assure consumption of most part of the nitrogen during the night. An improvement of the photosystem II maximum quantum yield and an increase in the dry weight and TAG concentration was achieved from day 7 of nitrogen starvation onwards when the culture was fed with nitrogen each night compared to a culture without nitrogen addition. Consequently, the time-average TAG yield on light was also higher after 7 days of nitrogen starvation. However, since the maximal time-averaged triacylglycerol (TAG) yield on light was reached after 3 days of nitrogen starvation, the improved photosynthetic activity did not lead to an increase of the maximal time-averaged TAG yield on light. The culture with nitrogen addition had a higher protein concentration (1.1 compared to 0.7 g L−1), showing that the added nitrogen was mainly used for protein production. A higher chlorophyll a content (2.0 compared to 0.8 μg mg−1) showed improved photosystem and that a small part of nitrogen was used for chlorophyll a. Small nightly nitrogen additions during batch cultivation of nitrogen starved N. gaditana did result in improvement in photosystem II maximal quantum yield, biomass concentration, TAG production and a higher time-averaged maximal TAG yield on light, after 7 days of nitrogen starvation.

      PubDate: 2018-05-29T04:18:03Z
      DOI: 10.1016/j.algal.2018.05.009
      Issue No: Vol. 33 (2018)
       
  • Biomass productivity of snow algae and model production algae under low
           temperature and low light conditions
    • Authors: Daniel P. Geller; K.C. Das; Thomas Bagby-Moon; Manjinder Singh; Gary Hawkins; Brian H. Kiepper
      Pages: 133 - 141
      Abstract: Publication date: July 2018
      Source:Algal Research, Volume 33
      Author(s): Daniel P. Geller, K.C. Das, Thomas Bagby-Moon, Manjinder Singh, Gary Hawkins, Brian H. Kiepper
      This study was designed to determine biomass productivities of specific algal species under low temperature and low light conditions. The algal species examined in this study included two psychrophilic algal species (Chlamydomonas yellowstonensis and Chlamydomonas augustae). These species are commonly known as “snow algae” due to their ability to grow in low temperature water bodies including ice and snow deposits. Additionally, two model production algal species used in high biomass productivity pilot studies (Scenedesmus bijuga and Chlorella sorokiniana) were evaluated. Currently, temperature dependent growth data within known optimal limits exists for these model production species but there is no detailed information about their biomass productivity under low temperatures. In addition, little information can be found about the potential for productivity of these species under limited light exposure. This study examined biomass productivity of these four species at four relatively low temperatures (5, 10, 15, and 20 °C) with three relatively low light exposures (50, 100, and 300 μmol/m2 s). It was hypothesized that the two psychrophilic algae species would produce more biomass per day than model production algal species under these limiting conditions. This study found that both snow algae species performed better than model production species at the lowest temperature (5 °C) and two lower light intensities (50 and100 μmol/m2/s). C. augustae growth rate was shown to have a positive correlation with temperature and a negative correlation with light intensity for the values observed in this study. This finding has significant implications for the use of C. augustae as a cool-season algal crop and a source of valuable genetic material for future engineering of algae. This could lead to the development of cool-season algal crops for sustainable, year-round, industrial production of algae in temperate climates. Furthermore, both of the snow algae species studied here showed inhibited growth at the highest light intensity studied here.

      PubDate: 2018-05-29T04:18:03Z
      DOI: 10.1016/j.algal.2018.05.005
      Issue No: Vol. 33 (2018)
       
  • Transcriptome analysis reveals the genetic foundation for the dynamics of
           starch and lipid production in Ettlia oleoabundans
    • Authors: Mark H.J. Sturme; Yanhai Gong; Josué Miguel Heinrich; Anne J. Klok; Gerrit Eggink; Dongmei Wang; Jian Xu; Rene H. Wijffels
      Pages: 142 - 155
      Abstract: Publication date: July 2018
      Source:Algal Research, Volume 33
      Author(s): Mark H.J. Sturme, Yanhai Gong, Josué Miguel Heinrich, Anne J. Klok, Gerrit Eggink, Dongmei Wang, Jian Xu, Rene H. Wijffels
      The oleaginous microalga Ettlia oleoabundans accumulates both starch and lipids to high levels under stress conditions such as nitrogen starvation (N−). To steer biosynthesis towards starch or lipids only, it is important to understand the regulatory mechanisms involved. Here physiological and transcriptional changes under nitrogen starvation were analysed in controlled flat-panel photobioreactors at both short and long time-scales. Starch accumulation was transient and occurred rapidly within 24 h upon starvation, while lipid accumulation was gradual and reached a maximum after 4 days. The major fraction of accumulated lipids was composed of de novo synthesized neutral lipids - triacylglycerides (TAG) - and was characterized by a decreased composition of the polyunsaturated fatty acids (PUFAs) C18:3 and C16:3 and an increased composition of the mono-unsaturated (MUFAs) and saturated (SFAs) fatty acids C18:1/C16:1 and C18:0/C16:0, respectively. RNA-sequencing revealed that starch biosynthesis and degradation genes show different expression dynamics from lipid biosynthesis ones. An immediate rapid increase in starch synthetic transcripts was followed by an increase in starch degrading transcripts and a decrease in the starch synthetic ones. In contrast, increased gene expression for fatty acid and TAG synthesis was initiated later and occurred more gradually. Expression of several fatty acid desaturase (FAD) genes was decreased upon starvation, which corresponds to the observed changes to higher levels of MUFAs and SFAs. Moreover, several homologs of transcription regulators that were implicated in controlling starch and lipid metabolism in other microalgae showed differential gene expression and might be key regulators of starch and lipid metabolism in E. oleoabundans as well. Our data provide insights into the genetic foundation of starch and lipid metabolism in E. oleoabundans under nitrogen starvation and should facilitate metabolic engineering towards tailored strains with desired storage compound composition.

      PubDate: 2018-05-29T04:18:03Z
      DOI: 10.1016/j.algal.2018.05.004
      Issue No: Vol. 33 (2018)
       
  • Catalytic hydrothermal liquefaction of spirulina to bio-oil in the
           presence of formic acid over palladium-based catalysts
    • Authors: Chunze Liu; Liping Kong; Yuanyuan Wang; Liyi Dai
      Pages: 156 - 164
      Abstract: Publication date: July 2018
      Source:Algal Research, Volume 33
      Author(s): Chunze Liu, Liping Kong, Yuanyuan Wang, Liyi Dai
      This paper reports our investigation of the catalytic hydrothermal liquefaction (HTL) of microalgae spirulina to bio-oil. Palladium-based catalysts Pd/HZSM-5@meso-SiO2 (Pd/HZSM-5@MS) and Pd/HZSM-5 were synthesized. X-ray diffraction analysis, scanning electron microscopy, and transmission electron microscopy were used to characterize the catalysts that were applied to the HTL of algae in the presence of formic acid. Elemental analysis and gas chromatography–mass spectrometry were used to analyze the resulting bio-oil. The characterizations indicated that the Pd/HZSM-5@MS-catalyzed HTL had a high bio-oil yield of 37.30% and a low coke yield of 8.56%, and that the obtained bio-oil contained no acids. Furthermore, this study suggests that Pd/HZSM-5 promoted hydrodenitrogenation of the bio-oil and that Pd/HZMS-5@MS promoted hydrodeoxygenation of the bio-oil. Catalyst recycling and the performance of the recycled catalyst were also investigated and discussed.
      Graphical abstract image

      PubDate: 2018-05-29T04:18:03Z
      DOI: 10.1016/j.algal.2018.05.012
      Issue No: Vol. 33 (2018)
       
  • Magnetic Fe3O4-polyethyleneimine nanocomposites for efficient harvesting
           of Chlorella zofingiensis, Chlorella vulgaris, Chlorella sorokiniana,
           Chlorella ellipsoidea and Botryococcus braunii
    • Authors: Kristína Gerulová; Alica Bartošová; Lenka Blinová; Katarína Bártová; Mária Dománková; Zuzana Garaiová; Marián Palcut
      Pages: 165 - 172
      Abstract: Publication date: July 2018
      Source:Algal Research, Volume 33
      Author(s): Kristína Gerulová, Alica Bartošová, Lenka Blinová, Katarína Bártová, Mária Dománková, Zuzana Garaiová, Marián Palcut
      A reduction in energy consumption at every stage of the down streaming process is needed to make 3rd generation of biofuels economically viable. In this study, magnetite (Fe3O4) nanoparticles were synthetized by coprecipitation of FeCl2 and FeCl3 in alkaline medium at two different temperatures. The particle sizes were 11.5 ± 4 and 9.5 ± 4 nm for the nanoparticles prepared at 80 °C and 25 °C, respectively. The adsorption of polyethyleneimine (PEI) onto Fe3O4 was studied by equilibrium batch measurements. A mono-layer absorption of PEI was found. The Fe3O4–PEI nanocomposites had a positive zeta potential, which decreased with increasing pH of the solution. The nanocomposites were used for magnetic harvesting of negatively charged Chlorella zofingiensis, Chlorella vulgaris, Chlorella sorokiniana, Chlorella ellipsoidea and Botryococcus braunii microalgae strains. Upon dosage of 200 mg/L of Fe3O4–PEI harvesting efficiencies of 68–97% were achieved at pH 4 within 1 min. The harvesting efficiency decreased with increasing pH of the suspension. The results demonstrate that Fe3O4 nanoparticles synthesized at the lower temperature (25 °C) could be used for an efficient magnetic harvesting of different microalgae strains. The lower synthesis temperature may thereby contribute to the cost reduction of microalgae harvesting.
      Graphical abstract image

      PubDate: 2018-05-29T04:18:03Z
      DOI: 10.1016/j.algal.2018.05.003
      Issue No: Vol. 33 (2018)
       
  • Shaping colour changes in a biofilm-forming cyanobacterium by modifying
           the culture conditions
    • Authors: B. Prieto; D. Vázquez-Nion; B. Silva; P. Sanmartín
      Pages: 173 - 181
      Abstract: Publication date: July 2018
      Source:Algal Research, Volume 33
      Author(s): B. Prieto, D. Vázquez-Nion, B. Silva, P. Sanmartín
      Cyanobacteria, pioneering microorganisms that create a conditioning layer on substrates and act as a source of nutrients for successive colonization by heterotrophic microbes, are commonly studied in relation to the microbial ecology of stones in indoor and outdoor habitats. They are well known for producing greenish-yellow, bluish-green or occasionally pink or pinkish-orange discolouration of surfaces. Such discolouration may be desirable for integrating new elements in landscapes and could be achieved by inoculating surfaces with cyanobacteria of a specific colour. In the present study, with the aim of producing cultures of perceptibly different hues, we modelled the colourimetric response of the biofilm-forming cyanobacterium Nostoc sp. PCC 9104 to variations in light intensity (L) and the concentrations of phosphorus (P) and nitrogen (N). The model obtained, which was validated from both mathematical and perceptual perspectives, enables production of cultures of a particular hue, within a range of 18° and with an efficacy of 92%. Coloured cultures of hue between 129° and 147°, corresponding to yellowish-green to bluish-green tones, were obtained by modifying nutrients inputs and the amount of light, without the need to resort to genetic manipulation.

      PubDate: 2018-05-29T04:18:03Z
      DOI: 10.1016/j.algal.2018.05.010
      Issue No: Vol. 33 (2018)
       
  • Investigation on models for light distribution of Haematococcus pluvialis
           during astaxanthin accumulation stage with an application case
    • Authors: Bin Sheng; Fei Fan; Jianke Huang; Wenmin Bai; Jun Wang; Sulan Li; Wei Li; Minxi Wan; Yuanguang Li
      Pages: 182 - 189
      Abstract: Publication date: July 2018
      Source:Algal Research, Volume 33
      Author(s): Bin Sheng, Fei Fan, Jianke Huang, Wenmin Bai, Jun Wang, Sulan Li, Wei Li, Minxi Wan, Yuanguang Li
      Light is an important stress factor for astaxanthin accumulation in H. pluvialis. Hence, the light distribution in the H. pluvialis suspension was investigated with biomass concentration from 0.218 g/L to 2.5 g/L during the astaxanthin accumulation stage. Lambert-Beer model and Cornet model were employed to predict the light attenuation. The result showed that Cornet model could slightly better describe and predict the light distribution in H. pluvialis suspension. Besides, Ea (absorption coefficient) and Es (scattering coefficient) were determined as 0.0126 ± 0.0036 m2/g and 0.223 ± 0.023 m2/g, respectively. Es increased with respect to astaxanthin content, whereas Ea declined with the increase of astaxanthin content. The astaxanthin content was the dominant factor at a relatively low mass concentration of H. pluvialis suspension. Furthermore, experiments were carried out in a 3 L-bubble-column PBR (photobioreactor) and a 12 L-bubble-column PBR. Higher volume-averaged light intensity and lower shear stress in 3 L PBR led to 66.67% higher astaxanthin content and 34.48% higher mass concentration than those of 12 L PBR during the outdoor experiment, respectively.

      PubDate: 2018-05-29T04:18:03Z
      DOI: 10.1016/j.algal.2018.05.011
      Issue No: Vol. 33 (2018)
       
  • Biological characterization of a strain of Golenkinia (Chlorophyceae) with
           high oil and carotenoid content induced by increased salinity
    • Authors: T.A. Rearte; C.G. Vélez; M.V. Beligni; F.L. Figueroa; P.I. Gómez; D. Flaig; A.F. de Iorio
      Pages: 218 - 230
      Abstract: Publication date: July 2018
      Source:Algal Research, Volume 33
      Author(s): T.A. Rearte, C.G. Vélez, M.V. Beligni, F.L. Figueroa, P.I. Gómez, D. Flaig, A.F. de Iorio
      The genus Golenkinia has not been studied for the production of metabolites of commercial interest. In this work, the accumulation and composition of oils and carotenoids was studied in a new isolated strain of the green alga Golenkinia sp. under salinity stress. Both the molecular and morphological characterization of the strain allowed us to identify it tentatively as G. brevispicula. As part of our morphological descriptions, we show previously unreported cellular stages. One of the most remarkable findings relates to the unprecedented observation of a reddish aplanospore stage in a Golenkinia strain resistant to desiccation. Salinity stress induced an increase in total lipids, reaching 37.2% of DW, and an increase in total carotenoids at the end of stress phase. According to the high lipid values with an equilibrated proportion of polyunsaturated fatty acids and the content of carotenoids dissolved in oil droplets, the lipids of this strain could have a potential application in the nutraceutical and aquaculture feed fields. Further studies are being conducted to optimize the growth and stress conditions in order to enhance biomass, oil and carotenoid productivity.

      PubDate: 2018-06-01T04:36:17Z
      DOI: 10.1016/j.algal.2018.05.014
      Issue No: Vol. 33 (2018)
       
  • Synergistic effect of co-culture of microalga and actinomycete in diluted
           chicken manure digestate for lipid production
    • Authors: Bancha Kumsiri; Jeeraporn Pekkoh; Wasu Pathom-aree; Saisamorn Lumyong; Chayakorn Pumas
      Pages: 239 - 247
      Abstract: Publication date: July 2018
      Source:Algal Research, Volume 33
      Author(s): Bancha Kumsiri, Jeeraporn Pekkoh, Wasu Pathom-aree, Saisamorn Lumyong, Chayakorn Pumas
      Microalgae have high potential as organisms that can be used for biodiesel production because they can accumulate high amounts of lipids in a similar manner to oleaginous plants. However, the economic feasibility of their lipid production is still in question. Possible methods of improving that feasibility involve a reduction in cultivation costs using effluents along with an increase in lipid production by co-cultivation with plant growth-supporting microorganisms. Previous studies have found that actinomycetes possess a potential as plant growth-promoters. Thus, this research study is aimed at investigating the effects of the co-cultivation of actinomycetes with microalgae on growth and lipid production in diluted chicken manure digestate. In this study, over 190 actinomycetes were screened for their ability to grow in the digestate, as well as for their plant growth promoting abilities. The actinomycete, Nocardia bhagyanarayanae I-27, could promote chlorophyll a, biomass and lipid contents in a co-culture with green microalga Tetradesmus obliquus AARL G022 in 25% diluted digestate. Microalgal major fatty acid methyl esters are a suitable substrate for biodiesel production. In addition, the essential Ω3 fatty acids, including α-linolenic acid and eicosapentaenoic acid, also increased in volume. Thus, the co-cultivation of plant growth promoting actinomycetes with microalgae in wastewater could be an alternative strategy used to increase biomass and lipid production.
      Graphical abstract image

      PubDate: 2018-06-01T04:36:17Z
      DOI: 10.1016/j.algal.2018.05.020
      Issue No: Vol. 33 (2018)
       
  • Redirecting carbon to bioproduction via a growth arrest switch in a
           sucrose-secreting cyanobacterium
    • Authors: Bradley W. Abramson; Josh Lensmire; Yang-Tsung Lin; Emily Jennings; Daniel C. Ducat
      Pages: 248 - 255
      Abstract: Publication date: July 2018
      Source:Algal Research, Volume 33
      Author(s): Bradley W. Abramson, Josh Lensmire, Yang-Tsung Lin, Emily Jennings, Daniel C. Ducat
      Cyanobacteria are microbes with high photosynthetic efficiencies, making them a promising target for the production of sustainable bioproducts directly from solar energy and carbon dioxide. The most common efforts to increase cyanobacterial bioproduction involve diverting cellular resources away from cellular biomass and towards a heterologous pathway, for example through nutrient starvation or knockout of genes in competing metabolic pathways. Here we show that an inducible cell growth arrest switch can be used to increase the partitioning of carbon to an engineered sucrose sink. Specifically, we show that overexpression of Regulator of Phycobilisome-Associated B (RpaB), an essential response regulator in Synechococccous elongatus PCC 7942, allows for inducible arrest of cell growth and is associated with a > 2-fold higher specific productivity of a heterologous sucrose secretion pathway. Finally, we show that sucrose export can partially relieve photosynthetic feedback inhibition imposed by the RpaB dependent growth arrest, allowing sucrose-secreting strains to maintain higher photosynthetic efficiencies. This work provides a novel conceptual framework for improving photosynthetic productivity and cyanobacterial bioproduction.

      PubDate: 2018-06-01T04:36:17Z
      DOI: 10.1016/j.algal.2018.05.013
      Issue No: Vol. 33 (2018)
       
  • Melatonin enhances astaxanthin accumulation in the green microalga
           Haematococcus pluvialis by mechanisms possibly related to abiotic stress
           tolerance
    • Authors: Wei Ding; Peng Zhao; Jun Peng; Yongteng Zhao; Jun-Wei Xu; Tao Li; Russel J. Reiter; Huixian Ma; Xuya Yu
      Pages: 256 - 265
      Abstract: Publication date: July 2018
      Source:Algal Research, Volume 33
      Author(s): Wei Ding, Peng Zhao, Jun Peng, Yongteng Zhao, Jun-Wei Xu, Tao Li, Russel J. Reiter, Huixian Ma, Xuya Yu
      Melatonin (N‑acetyl‑5‑methoxytryptamine) is widely regarded as an important messenger in higher plants and mammals in their resistance to various biotic and abiotic stresses. However, the role of melatonin in microalgae has been rarely investigated. In this study, melatonin was first used to promote astaxanthin biosynthesis under limited nitrogen and high light conditions. The interactions between melatonin and the secondary messengers, namely, nitric oxide (NO) and salicylic acid (SA), during the stress response were also investigated. Moreover, fatty acid biosynthesis was explored. Finally, the expression levels of astaxanthin biosynthesis genes in Haematococcus pluvialis LUGU supplemented with melatonin were simultaneously monitored through quantitative real-time PCR. The astaxanthin content of the microalgae increased 2.36-fold after treatment with 10 μM of melatonin. The maximal astaxanthin content achieved was 31.32 mg g−1. The increased NO and SA production caused by melatonin occurred in parallel with the up-regulation of the expression of astaxanthin biosynthesis genes and the enhancement in astaxanthin biosynthesis in H. pluvialis LUGU. The analysis of fatty acid composition showed that melatonin stimulated the production of C16:0 (palmitic acid); thus, the percentage of astaxanthin esters was higher than that observed in the control algae. Furthermore, the inhibitors, namely, carboxy-PTIO, paclobutrazol, and N‑acetyl‑l‑cysteine, significantly suppressed the levels of secondary messengers. Meanwhile, the role of melatonin in mediating the rise in astaxanthin content was prevented when the SA- and NO-dependent pathways were inhibited. These findings indicate that melatonin plays a physiological role in direct and indirect responses to abiotic stresses in H. pluvialis.

      PubDate: 2018-06-01T04:36:17Z
      DOI: 10.1016/j.algal.2018.05.021
      Issue No: Vol. 33 (2018)
       
  • Environmental influence on rotenone performance as an algal crop
           protective agent to prevent pond crashes for biofuel production
    • Authors: Waleed M.M. El-Sayed; Steven W. Van Ginkel; Thomas Igou; Hassan A. Ibrahim; Usama M. Abdul-Raouf; Yongsheng Chen
      Pages: 277 - 283
      Abstract: Publication date: July 2018
      Source:Algal Research, Volume 33
      Author(s): Waleed M.M. El-Sayed, Steven W. Van Ginkel, Thomas Igou, Hassan A. Ibrahim, Usama M. Abdul-Raouf, Yongsheng Chen
      Rotenone as an algal crop protective agent has the potential to be a promising, inexpensive tool for algal biofuel productivity enhancement due to its ability to inhibit zooplankton in algaculture. This study focuses on the potential impact of various physical and chemical factors affecting rotenone persistence during algal cultivation for biofuel production. The roles of light, temperature, pH, cultivation medium and adsorption to algal biomass were evaluated. Chlorella kessleri was used as the model oleaginous microalgae in this study. Temperature increased the rate of rotenone degradation, with average degradation rates ranging from 1 ± 0.8 mg/L-h to 3.6 ± 1.5 mg/L-h as the temperature increased from 15 °C to 35 °C. Increased pH also raised the rate of degradation from 1.0 ± 0.9 to 3.4 ± 1.7 mg/L-h as the pH increased from 7 to 10. In contrast, light had little effect on rotenone degradation compared to dark conditions (p = 0.324). BG-11 medium also increased rotenone degradation from an average of 1.7 ± 0.7 to 2.8 ± 0.8 mg/L-h. Adsorption capacity, as evaluated by the Langmuir and Freundlich isotherms, was found to be 0.77 and 0.70 mg rotenone/g of C. kessleri biomass, respectively. These findings were used to develop discrete dosing strategies to be utilized by operators. With respect to minimum required concentrations, both degradation and adsorption were found to be significant sources of rotenone removal and should be considered when proposing a dosing strategy for algal crop protection.

      PubDate: 2018-06-10T05:25:29Z
      DOI: 10.1016/j.algal.2018.05.015
      Issue No: Vol. 33 (2018)
       
  • Influence of alkalinity and temperature on photosynthetic biogas upgrading
           efficiency in high rate algal ponds
    • Authors: María del Rosario Rodero; Esther Posadas; Alma Toledo-Cervantes; Raquel Lebrero; Raúl Muñoz
      Pages: 284 - 290
      Abstract: Publication date: July 2018
      Source:Algal Research, Volume 33
      Author(s): María del Rosario Rodero, Esther Posadas, Alma Toledo-Cervantes, Raquel Lebrero, Raúl Muñoz
      Algal-bacterial photobioreactors have emerged as a cost-effective platform for biogas upgrading. The influence on biomethane quality of the inorganic carbon concentration (1500, 500 and 100 mg L−1) and temperature (12 and 35 °C) of the cultivation broth was evaluated in a 180 L high rate algal pond (HRAP) interconnected to a 2.5 L absorption column via settled broth recirculation. The highest CO2 and H2S removal efficiencies (REs) from biogas were recorded at the highest alkalinity (CO2-REs of 99.3 ± 0.1 and 97.8 ± 0.8% and H2S-REs of 96.4 ± 2.9 and 100 ± 0% at 12 and 35 °C, respectively), which resulted in CH4 concentrations of 98.9 ± 0.2 and 98.2 ± 1.0% at 12 and 35 °C, respectively, in the upgraded biogas. At the lowest alkalinity, the best upgrading performance was observed at 12 °C (CO2 and H2S-REs of 41.5 ± 2.0 and 80.3 ± 3.9%, respectively). The low recycling liquid to biogas ratio applied (0.5) resulted in a negligible O2 stripping regardless of the alkalinity and temperature, which entailed a biomethane O2 content ranging from 0 to 0.2 ± 0.3%.
      Graphical abstract image

      PubDate: 2018-06-10T05:25:29Z
      DOI: 10.1016/j.algal.2018.06.001
      Issue No: Vol. 33 (2018)
       
  • The responses of two genes encoding phytoene synthase (Psy) and phytoene
           desaturase (Pds) to nitrogen limitation and salinity up-shock with special
           emphasis on carotenogenesis in Dunaliella parva
    • Authors: Changhua Shang; Wen Wang; Shunni Zhu; Zhongming Wang; Lei Qin; Mohammad Asraful Alam; Jun Xie; Zhenhong Yuan
      Pages: 1 - 10
      Abstract: Publication date: June 2018
      Source:Algal Research, Volume 32
      Author(s): Changhua Shang, Wen Wang, Shunni Zhu, Zhongming Wang, Lei Qin, Mohammad Asraful Alam, Jun Xie, Zhenhong Yuan
      Green alga Dunaliella parva can adapt to environmental stresses such as salinity up-shock and nitrogen limitation which are associated with carotenoid accumulation. However, the underlying molecular basis related to the change of carotenoid content needs further study. In the present study, we cloned two carotenoid biosynthesis genes coding for phytoene synthase and phytoene desaturase. In addition, the effects of salinity up-shock and nitrogen limitation on carotenoid content and expression of these two genes were studied in D. parva FACHB-815. The results showed that both salinity up-shock and nitrogen limitation had important effect on carotenoid yield and expression of these two genes. Cloning and expression analysis of these two genes will contribute to the understanding of molecular basis in stress-induced carotenoid accumulation, which is favorable for performing metabolic and genetic engineering to improve traits of D. parva.

      PubDate: 2018-03-18T15:48:21Z
      DOI: 10.1016/j.algal.2018.03.002
      Issue No: Vol. 32 (2018)
       
  • Isolation and characterization of microalgal strains for biomass
           production and wastewater reclamation in Northern Sweden
    • Authors: Lorenza Ferro; Francesco G. Gentili; Christiane Funk
      Pages: 44 - 53
      Abstract: Publication date: June 2018
      Source:Algal Research, Volume 32
      Author(s): Lorenza Ferro, Francesco G. Gentili, Christiane Funk
      Microalgal strains adapted to the harsh Nordic climate were isolated from Swedish fresh- and wastewater sources and tested for their ability to grow in municipal wastewater. The 62 strains able to grow in municipal wastewater belonged to 12 different genera, of those Desmodesmus, Scenedesmus and Chlorella were most representative. Eight axenic strains were further characterized, all of which could efficiently remove nitrogen (>90%) and phosphate (>99%) from the wastewater in less than two weeks. The microalga Coelastrella sp. had the highest performance in terms of both biomass concentration and total lipid content (1.46 g/L, 30.8%) after 13 days of cultivation. This is the first report of a Coelastrella strain isolated in Sweden. Even Chlorella vulgaris performed very well with a biomass concentration and total lipid content of 1.15 g/L and 34.2%, respectively. Finally, two Desmodesmus sp. strains showed desirable traits for biofuel-feedstock, due to their fast growth rates (1.18 and 1.08 d−1) together with high oil content (29.8% and 36.7% of DW).

      PubDate: 2018-04-15T04:40:39Z
      DOI: 10.1016/j.algal.2018.03.006
      Issue No: Vol. 32 (2018)
       
  • Low-cost optical sensor to automatically monitor and control biomass
           concentration in microalgal cultivation
    • Authors: Binh T. Nguyen; Bruce E. Rittmann
      Pages: 101 - 106
      Abstract: Publication date: June 2018
      Source:Algal Research, Volume 32
      Author(s): Binh T. Nguyen, Bruce E. Rittmann
      Low productivity of microalgal cultures leads to a high cost of the fuel feedstock. Turbidostat operation, which automatically monitors and controls biomass density, is a mean to manage biomass density and internal light intensity, so that biomass productivity can be maximized. Available versions of turbidostat control are expensive and not amenable to large-scale operation. We designed a system that costs less than $250 and that can be used for any type of microbiological system. It includes an in-line, infrared turbidity sensor connected to an Arduino ATmega microcontroller and auxiliary power replays. The target biomass density is adjustable, and key operating data – such as time stamps, pump status, and set and measured values of biomass density – are available in real time and logged continuously. The sensor's output was linear for OD730 from 0.5 to 4.5, which brackets the realistic ranges for microalgae culturing. We tested the turbidostat with step-down and step-up experiments with Synechocystis cultures. The turbidostat maintained stable biomass concentrations for all steps. The results of the turbidostat experiments demonstrated how turbidity control leads to systematic management of average internal light intensity, specific growth rate, and biomass production rate. This open-design, low-cost system should promote higher productivity and help make microalgae biomass an affordable fuel feedstock.
      Graphical abstract image

      PubDate: 2018-04-15T04:40:39Z
      DOI: 10.1016/j.algal.2018.03.013
      Issue No: Vol. 32 (2018)
       
  • Pilot-scale production of antibacterial substances by the marine diatom
           Phaeodactylum tricornutum Bohlin
    • Authors: Song Wang; Inamullah Hakeem Said; Candice Thorstenson; Claudia Thomsen; Matthias S. Ullrich; Nikolai Kuhnert; Laurenz Thomsen
      Pages: 113 - 120
      Abstract: Publication date: June 2018
      Source:Algal Research, Volume 32
      Author(s): Song Wang, Inamullah Hakeem Said, Candice Thorstenson, Claudia Thomsen, Matthias S. Ullrich, Nikolai Kuhnert, Laurenz Thomsen
      The production and extraction of antibacterial substances from Phaeodactylum tricornutum biomass were tested on a pilot scale in a photo-bioreactor greenhouse installation. Using column chromatography two antibacterial active fractions were obtained from the algal biomass: a pure fraction of eicosapentaenoic acid (EPA) and a potentially new antibacterial substance(s) (identified as fraction B) produced by P. tricornutum. Both fractions exhibited antibacterial activities against three human pathogens: Vibrio vulnificus, V. parahaemolyticus, and V. cholerae. Minimal inhibitory concentrations against Bacillus subtilis of active fractions and one antibacterial commercial product were determined revealing a higher antibacterial activity of EPA in comparison to the commercial product. Consequently, EPA as well as the raw algal biomass with both EPA and the fraction B compounds could be used as food additives and feeds in aquaculture, poultry, and livestock breeding. Two types of phytohormones, methyl jasmonate and salicylic acid, as well as one phytotoxin, coronatine, were tested for induction of the defense system of P. tricornutum. However, only a minor change in the fatty acids profile and antibacterial effects of the treated cultures indicated that P. tricornutum must employ another strategy to regulate its antibacterial defense system.

      PubDate: 2018-04-15T04:40:39Z
      DOI: 10.1016/j.algal.2018.03.014
      Issue No: Vol. 32 (2018)
       
  • Kinetic modelling of microalgae cultivation for wastewater treatment and
           carbon dioxide sequestration
    • Authors: Valentine C. Eze; Sharon B. Velasquez-Orta; Andrea Hernández-García; Ignacio Monje-Ramírez; María T. Orta-Ledesma
      Pages: 131 - 141
      Abstract: Publication date: June 2018
      Source:Algal Research, Volume 32
      Author(s): Valentine C. Eze, Sharon B. Velasquez-Orta, Andrea Hernández-García, Ignacio Monje-Ramírez, María T. Orta-Ledesma
      A simple and robust microalgae kinetic model has been developed for application in the prediction and control of algae cultivations in wastewater. The microalgae kinetic model was calibrated using experimental cultivation data from Desmodesmus sp. to determine specific microalgae growth rates (μ max and μ maxNO3), microalgae death rates (μ d ), and the NH4 + to NO3 − oxidation rate (μ B ). Model parameters obtained were: μ max  = 0.17 day−1, μ d  = 0.004 day−1, and μ B  = 0.14 day−1. Microalgae specific growth rate based on NO3 − alone (μ maxNO3 = 0.1 day−1) was lower than the overall growth rate (μ max ). The kinetic model was validated using additional experimental data for the Desmodesmus sp. and Scenedesmus obliquus cultivation in wastewater containing 0% and 7% landfill leachate, with accuracy above 98% in all cases. These results demonstrated the kinetic model was accurate in predicting microalgae growth, wastewater nutrient removal, and changes in the culture media pH. Biomass productivity of the algae culture was associated with an exponential increase in the media pH, which led to ammonia volatilisation and decreased carbon intake. Between 28.8 and 29.7% of the initial NH4 + was lost to ammonia volatilisation in wastewater containing 7% landfill leachate. Hence, loss of ammonium nitrogen contained in domestic wastewater must be avoided to ensure steady and efficient inorganic carbon utilisation which inherently maximises biomass production efficiency. The optimal pH for the microalgae culture was 8.1, at which point microalgae could achieve about 99% carbon fixation efficiency. To ensure constant pH in the microalgae growing system, immediate removal of the OH− generated is needed, which could be facilitated by injections of 1.14 g CO2 and 0.067 g OH− per gram of produced algae when using NH4 + nutrient, and 1.54 g of CO2 per gram of produced algae when using NO3 − nutrient. This could be done in a wastewater pond by using an optical density-controlled smart CO2 injection system.
      Graphical abstract image

      PubDate: 2018-04-15T04:40:39Z
      DOI: 10.1016/j.algal.2018.03.015
      Issue No: Vol. 32 (2018)
       
  • Effects of extracts and isolated molecules of two species of Gracilaria
           (Gracilariales, Rhodophyta) on early growth of lettuce
    • Authors: Priscila Torres; Paula Novaes; Luciana Garcia Ferreira; Janaína Pires Santos; Ester Mazepa; Maria Eugênia R. Duarte; Miguel D. Noseda; Fungyi Chow; Deborah Y.A.C. dos Santos
      Pages: 142 - 149
      Abstract: Publication date: June 2018
      Source:Algal Research, Volume 32
      Author(s): Priscila Torres, Paula Novaes, Luciana Garcia Ferreira, Janaína Pires Santos, Ester Mazepa, Maria Eugênia R. Duarte, Miguel D. Noseda, Fungyi Chow, Deborah Y.A.C. dos Santos
      Crude extracts using hexane, dichloromethane, methanol, 80% methanol or water of two agarophytes (Gracilaria caudata and Gracilaria domingensis) and their phase partitions were evaluated on early growth of lettuce. Hexane, methanol, 80% methanol and aqueous extracts of G. caudata and dichloromethane and aqueous extracts of G. domingensis were biostimulants. Palmitic acid, the major compound of non-polar extracts and phase partition, showed a significant stimulant activity in the concentrations tested (ranging from 0.49 mM to 1.95 mM), increasing 83% of lettuce root length, comparing to control, at the highest concentration. The promoting effect of the aqueous extracts is probably related to the presence of agaran, a typical hydrocolloid polysaccharide from red algae, which is mostly an exclusive constituent of these extracts. The agarans of G. domingensis and G. caudata promoted an increase in lettuce root length of 60% and 40%, respectively (both at 1 mg·mL−1 of extract). Differences in the effects promoted by these two agarans are probably related to the different content of sulfate groups (higher for polysaccharide from G. domingensis). These results suggest that structural features of agaran-type polysaccharides can elicit distinct responses. To the best of our knowledge, this is the first report on the identification of compounds with biostimulating potential from Gracilaria.

      PubDate: 2018-04-15T04:40:39Z
      DOI: 10.1016/j.algal.2018.03.016
      Issue No: Vol. 32 (2018)
       
  • Microalgal bioremediation of nitrogenous compounds in landfill leachate
           – The importance of micronutrient balance in the treatment of leachates
           of variable composition
    • Authors: Andrea Paskuliakova; Ted McGowan; Steve Tonry; Nicolas Touzet
      Pages: 162 - 171
      Abstract: Publication date: June 2018
      Source:Algal Research, Volume 32
      Author(s): Andrea Paskuliakova, Ted McGowan, Steve Tonry, Nicolas Touzet
      Landfill leachate is a type of wastewater which is challenging to treat. Phycoremediation has been proposed as an alternative biological treatment for removal of ammonia nitrogen. Several studies have shown microalgae based bioremediation to be possible with ammonia tolerant microalgal species, provided that an optimal dilution is used and the initial molecular N:P ratio is adjusted. The composition of landfill leachate varies between sites and throughout the year. The performance of selected microalgal strains and their susceptibility to variation in landfill leachate composition is poorly understood. This study compares the growth of Chlamydomonas sp. strain SW15aRL in a variety of leachate samples. The leachate samples are from different sites including leachate sampled on different occasions from the same site. These substrates were diluted to obtain ammonia nitrogen concentration within the range of 30 to 220 mg·l−1. Results showed that strain SW15aRL was capable of growth in a variety of leachates but was dependent on the overall composition profile of the landfill leachate rather than just its dilution. Growth was negatively affected in two of the leachates tested, due to metal toxicity and mineral bioavailability or deficiency. Phosphate addition was essential for growth in the landfill leachates even though precipitation occurred in some instances. Ammonia nitrogen decrease varied between 70% and 100% in the substrates where microalgae could successfully grow. This study indicates that due to their overall mineral profile some landfill leachates are more suited for microalgae based remediation than others. Furthermore, this study indicates that a better understanding of other physicochemical processes that take place concurrently during the growth of microalgae in landfill leachate and which contribute to overall nutrient reduction is required.

      PubDate: 2018-04-15T04:40:39Z
      DOI: 10.1016/j.algal.2018.03.010
      Issue No: Vol. 32 (2018)
       
  • Dynamic response of Synechocystis sp. PCC 6803 to changes in light
           intensity
    • Authors: Levi Straka; Bruce E. Rittmann
      Pages: 210 - 220
      Abstract: Publication date: June 2018
      Source:Algal Research, Volume 32
      Author(s): Levi Straka, Bruce E. Rittmann
      With changing light intensities, microalgae exhibit the inter-connected phenomena of photoacclimation, photodamage, and photodamage repair. Together they result in unique growth responses to changes in light intensity. In this work, we experimentally evaluated the growth responses using Synechocystis sp. PCC 6803 subjected to a series of light-step experiments. In these experiments, the biomass density and average light intensity were held constant (after the step in light intensity), and the dynamic response of the specific growth rate was measured. The over-arching trend is that an increasing-light step gave a rapid spike in growth rate, followed by a depression and ultimately restabilization of the growth rate for the new light condition. A decreasing-light step led to a small depression in growth rate before a gradual restabilization for the new light condition. Photoacclimation was faster after an increasing-light step than a decreasing-light step. Using a model accounting for photoacclimation, photodamage, and photodamage repair (presented in a companion paper), we captured the dynamic growth response and explained how the responses were the result of the combined effects of light absorption, photoacclimation, and photodamage.
      Graphical abstract image

      PubDate: 2018-04-25T01:46:25Z
      DOI: 10.1016/j.algal.2018.04.004
      Issue No: Vol. 32 (2018)
       
  • Multi-parametric modelling and kinetic sensitivity of microalgal cells
    • Authors: Hamzat Tijani; Ali Yuzir; Wan Rosmiza Zana Wan Dagang; Arash Zamyadi; Norhayati Abdullah
      Pages: 259 - 269
      Abstract: Publication date: June 2018
      Source:Algal Research, Volume 32
      Author(s): Hamzat Tijani, Ali Yuzir, Wan Rosmiza Zana Wan Dagang, Arash Zamyadi, Norhayati Abdullah
      Mathematical modelling is a cognitive tool employed to describe the cellular response of microalgal cells to changes in nutrient inputs and other environmental factors. Currently, there exists no accurate model that simultaneously incorporates multi-parametric inputs such as carbon, nitrogen, phosphorus and light intensity as defining parameters for algae life. The main objective of this study is to develop mathematical models based on the defining four parametric inputs (i.e. carbon, nitrogen, phosphorus and light intensity) via Monod, Haldane, and Droop kinetics. These models were correlated with the growth data of microalgal cells in nutrient-saturated continuous cultures. Observed data did not conformed to the extended Monod and Haldane kinetics, but correlated to the extended Droop kinetics. The extended Droop kinetics (eDK) projected a similar trend in cell proliferation and response trajectory with the real-time experimental data. However, these model projections showed different transient dynamics in response to changes in the concentration of incoming nutrients in time-course simulations. Such differences suggest that the choice between Monod, Haldane and Droop kinetics to model the non-equilibrium dynamics of photosynthetic cells leads to widely divergent predictions of biomass proliferation. The mass transfer coefficient (k l . a), is the most sensitive parametric input for biomass synthesis with maximum influence on the growth response trajectory.

      PubDate: 2018-04-25T01:46:25Z
      DOI: 10.1016/j.algal.2018.04.009
      Issue No: Vol. 32 (2018)
       
  • How to combine CO2 abatement and starch production in Chlorella vulgaris
    • Authors: Rafael García-Cubero; José Moreno-Fernández; F.G. Acién-Fernández; Mercedes García-González
      Pages: 270 - 279
      Abstract: Publication date: June 2018
      Source:Algal Research, Volume 32
      Author(s): Rafael García-Cubero, José Moreno-Fernández, F.G. Acién-Fernández, Mercedes García-González
      Microalgae production has gained attention in recent years as promising systems for CO2 abatement as well as a source of proteins, pigments, vitamins, lipids, and carbohydrates. Particularly, starch can be used for bioethanol production in a well-established fermentative process. The aim of this work was to maximize and model biomass productivity and CO2 assimilation in continuous cultures of Chlorella vulgaris. The following culture parameters were studied: dilution rate, pH, temperature, light intensity, and nitrogen supply. The proposed model (r2 = 0.95) predicted a maximum biomass productivity of 0.7 g L−1 d−1 and CO2 assimilation of 1.3 g L−1 d−1. The experimental data agreed with these predictions, resulting in a maximum biomass productivity of 0.67 g L−1 d−1 (resulting in a CO2 assimilation of 1.23 g L−1 d−1). In addition, the starch content was determined, and the results were used as input into a second model, which aimed at predicting starch accumulation during CO2 abatement processes (r2 = 0.84). This second model predicted a daily and continuous production of biomass with a maximum starch content of 0.25 g g−1 d−1 (25% dcw), but under different culture conditions than those found for maximizing biomass productivity and CO2 assimilation. The maximum starch content experimentally determined was 0.2 g g−1 d−1 (20% dcw). Thus, to implement a biological system for CO2 abatement coupled to starch accumulation, it is necessary to find a compromise between these two processes. Hence, although yield in both processes would be reduced, a simultaneous process for CO2 mitigation and starch production would be feasible.

      PubDate: 2018-04-25T01:46:25Z
      DOI: 10.1016/j.algal.2018.04.006
      Issue No: Vol. 32 (2018)
       
  • Effects of air bubble size on algal growth rate and lipid accumulation
           using fine-pore diffuser photobioreactors
    • Authors: Zhigang Yang; Haiyan Pei; Fei Han; Yuting Wang; Qingjie Hou; Yang Chen
      Pages: 293 - 299
      Abstract: Publication date: June 2018
      Source:Algal Research, Volume 32
      Author(s): Zhigang Yang, Haiyan Pei, Fei Han, Yuting Wang, Qingjie Hou, Yang Chen
      Microalgae are a potential feedstock for biodiesel and aeration is a reliable method to improve the growth of microalgae. Previous studies revealed the influence of bubbles on a variety of microorganisms, yet so far few studies have focused on the effects of bubble size on microalgal lipid production. In this study, four different fine-pore diffusers that could produce different bubble sizes were used for aeration in the photobioreactors. The equivalent diameters (d e) of the bubbles in the four systems were 1.5 mm, 2.5 mm, 3.5 mm and 6.0 mm, respectively. The system with d e = 3.5 mm obtained the highest biomass productivity (104.1 mg·L−1·d−1), which was 12% higher than that with d e = 1.5 mm. However, the lipid content in the system with d e = 1.5 mm was 30% higher than that for d e = 3.5 mm, and it also achieved the highest lipid productivity of 30.4 mg·L−1·d−1. Results from transmission electron microscope indicated that there is more starch in the cells when d e = 3.5 mm and more lipid droplets in the cells when d e = 1.5 mm. The largest bubble size was not beneficial for supplementing CO2 to the algae, which may have limited the growth. Therefore the air bubble size of d e = 1.5 mm is the best when using aeration as a strategy for enhancing lipid productivity, since it could provide appropriate external stress for lipid accumulation, but did not greatly inhibit the growth of microalgae.

      PubDate: 2018-05-29T04:18:03Z
      DOI: 10.1016/j.algal.2018.04.016
      Issue No: Vol. 32 (2018)
       
  • Lipid productivity in TALEN-induced starchless mutants of the unicellular
           green alga Coccomyxa sp. strain Obi
    • Authors: Keita Takahashi; Yoko Ide; Jumpei Hayakawa; Yuya Yoshimitsu; Izumi Fukuhara; Jun Abe; Yuki Kasai; Shigeaki Harayama
      Pages: 300 - 307
      Abstract: Publication date: June 2018
      Source:Algal Research, Volume 32
      Author(s): Keita Takahashi, Yoko Ide, Jumpei Hayakawa, Yuya Yoshimitsu, Izumi Fukuhara, Jun Abe, Yuki Kasai, Shigeaki Harayama
      Starchless mutants of several green algae including Chlamydomonas reinhardtii and Scenedesmus obliquus showed improved lipid productivity. In this study, we isolated mutants of the unicellular green alga, Coccomyxa sp. strain Obi, defective in the gene for the large subunit of ATP:α-d-glucose-1-phosphate adenylyltransferase (AGPL) by means of a transcription activator-like effector nuclease (TALEN) as follows. First, two expression cassettes encoding left and right arms of TALEN for AGPL mutagenesis were introduced into strain Obi, and from two independent transformants of strain Obi carrying both expression cassettes, seven derivatives bearing different mutations in AGPL were isolated. When these mutants were grown in 1/2-diluted and 1/3-diluted minimal media, their lipid contents were significantly higher than those of their parental strains. The growth in 1/3-diluted medium was similar between the mutants and their parental strains, while the growth in 1/2-diluted medium was significantly lower for the mutants than for their parental strains. The lipid productivity, which is a crucial factor for commercial production of biofuels, was not statistically different between the parental and mutant strains. We concluded that the suppression of starch biosynthesis to increase lipid productivity in microalgae is a risky strategy as it could result in low biomass productivity.

      PubDate: 2018-05-29T04:18:03Z
      DOI: 10.1016/j.algal.2018.04.020
      Issue No: Vol. 32 (2018)
       
  • Magnetic beads, a particularly effective novel method for extraction of
           NGS-ready DNA from macroalgae
    • Authors: Antoine Fort; Michael D. Guiry; Ronan Sulpice
      Pages: 308 - 313
      Abstract: Publication date: June 2018
      Source:Algal Research, Volume 32
      Author(s): Antoine Fort, Michael D. Guiry, Ronan Sulpice
      Next Generation Sequencing (NGS) technologies allow for the generation of robust information on the genetic diversity of organisms at the individual, species and higher taxon levels. Indeed, the number of single nucleotide polymorphisms (SNPs) detected using next-generation sequencing is order of magnitudes higher than SNPs and/or alleles detected using traditional barcoding or microsatellites. However, the amount and quality of DNA required for next-generation sequencing is greater as compared with PCR-based methods. Such high DNA amount and quality requirements can be a hindrance when working on species that are rich in polyphenols and polysaccharides, such as macroalgae (seaweeds). Various protocols, based on column-based DNA extraction kits and CTAB/Phenol:Chloroform, are available to tackle this issue. However, those protocols are usually costly and/or time-consuming and may not be reliable due to variations in the polyphenols/polysaccharide content between individuals of the same species. Here, we report the successful use of a magnetic-beads-based protocol for efficient, reliable, fast and simultaneous DNA extraction of several macroalgae species. DNA extracted from macroalgae using this method is of high quality and purity, allowing successful library preparation for next generation sequencing. We generated Genotype-By-Sequencing (GBS) data for 12 Ulva spp. (Sea Lettuce; Ulvophyceae, Ulvaceae) individuals and were able to generate a robust phylogenetic tree that we compared with traditional barcoding methods.

      PubDate: 2018-05-29T04:18:03Z
      DOI: 10.1016/j.algal.2018.04.015
      Issue No: Vol. 32 (2018)
       
  • A novel predatory bacterium infecting the eukaryotic alga Nannochloropsis
    • Authors: Philip A. Lee; Kalli J.L. Martinez; Peter M. Letcher; Alina A. Corcoran; Rebecca A. Ryan
      Pages: 314 - 320
      Abstract: Publication date: June 2018
      Source:Algal Research, Volume 32
      Author(s): Philip A. Lee, Kalli J.L. Martinez, Peter M. Letcher, Alina A. Corcoran, Rebecca A. Ryan
      Cultivation of algae in outdoor ponds is a cost-effective method to produce algal bioproducts for various economic sectors including agriculture, fuel and cosmetics. However, like any agricultural system, the algal crop is susceptible to a variety of pests, many of which are not described in the literature. This knowledge gap precludes the development of effective treatments and, in turn, limits the viability of the algal cultivation industry. Here we describe a novel pleomorphic bacterial predator (henceforth FD111) of the eukaryotic alga Nannochloropsis, which we identified as a causal agent of culture loss in outdoor ponds. Transmission electron microscopy revealed that FD111 has an endobiotic life cycle similar to described predatory bacteria, but previously undescribed for a eukaryotic host. A putative sequence for FD111 shows similarity to bacteria within the order Bdellovibrionales. Primers were developed for this sequence allowing the monitoring of infection by qPCR. Sodium hypochlorite is presented as a potential treatment to prevent culture loss caused by FD111 infection. FD111 is an amenable model organism for studying algae-bacteria interactions and is relevant to disciplines from evolutionary biology to biotechnology.

      PubDate: 2018-05-29T04:18:03Z
      DOI: 10.1016/j.algal.2018.04.003
      Issue No: Vol. 32 (2018)
       
  • Microalgal CO2 capture at extreme pH values
    • Authors: Jonna Piiparinen; Dorothee Barth; Niels T. Eriksen; Sebastian Teir; Kristian Spilling; Marilyn G. Wiebe
      Pages: 321 - 328
      Abstract: Publication date: June 2018
      Source:Algal Research, Volume 32
      Author(s): Jonna Piiparinen, Dorothee Barth, Niels T. Eriksen, Sebastian Teir, Kristian Spilling, Marilyn G. Wiebe
      Although algae are often grown at pH values between 6 and 8, shifting to more alkali or acidic conditions may benefit CO2 delivery to algal cultures. To assess the impact of culture pH on growth rate and uptake of CO2, we grew three relatively fast growing acidophilic (Coccomyxa sp., Euglena mutabilis and Euglena gracilis) and three alkaliphilic (Thalassiosira pseudonana, Phaeodactylum tricornutum, Chlamydomonas sp.) algal species at pH values near neutral and near the extreme of their growth range. All six species showed similar growth and CO2 uptake ability at extreme as at neutral pH values. Cultures of the alkaliphilic species captured a higher proportion of CO2 from the gas stream than the acidophilic species; removing 50 to 65% of CO2 from air compared to only 38% removed by acidophilic species (or 10–24% from CO2 enriched air). Alkaliphilic species did not become carbon limited when fed CO2 at the concentration provided by air (0.04% CO2), but produced less biomass and captured less total CO2 (0.06 to 0.08 g CO2 per day) than the acidophilic species (0.6–0.8 g CO2 day−1) which required CO2 enriched air to avoid carbon limitation. Bicarbonate feeding reduced the loss of CO2 to the environment, compared to feeding gaseous CO2, but with a potential cost in reduced specific growth rate or biomass production.

      PubDate: 2018-05-29T04:18:03Z
      DOI: 10.1016/j.algal.2018.04.021
      Issue No: Vol. 32 (2018)
       
  • Optimising light conditions increases recombinant protein production in
           Chlamydomonas reinhardtii chloroplasts
    • Authors: Saskya E. Carrera Pacheco; Ben Hankamer; Melanie Oey
      Pages: 329 - 340
      Abstract: Publication date: June 2018
      Source:Algal Research, Volume 32
      Author(s): Saskya E. Carrera Pacheco, Ben Hankamer, Melanie Oey
      The green alga Chlamydomonas reinhardtii provides a platform for cheap, scalable and safe production of complex proteins. Despite the fact that chloroplast gene expression in photosynthetic organisms is tightly regulated by light, most expression studies have analysed chloroplast recombinant protein production under constant light. Here, the influence of light period and intensity on expression of green fluorescent protein (GFP) and a GFP-bacterial-lysin (PlyGBS) fusion protein was analysed. Protein yields were strongly influenced by the light period (6–24 h d−1), the light intensity (0–450 μE m−2 s−1) and trophic condition. Heterotrophic conditions showed low yields of both recombinant proteins due to low growth rates, despite high protein accumulation per cell. Mixotrophic conditions exhibited the highest yields for GFP (4 mg·L−1·d−1) under constant light at 35 μE m−2 s−1 and GFP-PlyGBS (0.4 mg·L−1·d−1) under a light period of 15 h d−1 and 35 μE m−2 s−1. This is due to the high growth rates and cellular protein content. For GFP-PlyGBS the maximum increase in cellular protein accumulation was ~24-fold, and in total protein yield ~10-fold, in comparison to constant light conditions (~200 μE m−2 s−1). The highest yields under photoautrophic conditions were obtained under a 9 h d−1 light period. GFP yielded 1.2 mg·L−1·d−1 and GFP-PlyGBS 0.42 mg·L−1·d−1. This represented a ~5-fold increase in cellular protein accumulation for GFP-PlyGBS in comparison to constant light conditions (~200 μE m−2 s−1). Optimising light conditions to balance growth and protein expression can significantly enhance overall recombinant protein production in C. reinhardtii cultures.

      PubDate: 2018-05-29T04:18:03Z
      DOI: 10.1016/j.algal.2018.04.011
      Issue No: Vol. 32 (2018)
       
  • Efficacy of Spirulina sp. polyhydroxyalkanoates extraction methods and
           influence on polymer properties and composition
    • Authors: Samantha Serra Costa; Andréa Lobo Miranda; Bianca Bomfim Andrade; Denilson de Jesus Assis; Carolina Oliveira Souza; Michele Greque de Morais; Jorge Alberto Vieira Costa; Janice Izabel Druzian
      Pages: 552 - 562
      Abstract: Publication date: July 2018
      Source:Algal Research, Volume 33
      Author(s): Samantha Serra Costa, Andréa Lobo Miranda, Denilson de Jesus Assis, Carolina Oliveira Souza, Michele Greque de Morais, Jorge Alberto Vieira Costa, Janice Izabel Druzian
      The objective of this study was to evaluate the efficacy of methods used to extract polyhydroxyalkanoates from Spirulina sp. LEB-18 microalgae and to examine the influence of these methods on the purity, properties, and composition of the polymers. Polyhydroxyalkanoates were characterized by Fourier transform infrared spectroscopy (FTIR), molecular mass, degree of crystallinity, and monomer composition. The efficacy of the extraction methods varied, with polyhydroxyalkanoate accumulation. between 6.10 and 9.80%, and degrees of purity between 63.51 and 93.62%. Using sodium hypochlorite in the initial stage of the extraction increased accumulation, while using methanol at the end of the process increased the purity of the polymers. The molecular mass and crystallinity index of the polyhydroxyalkanoates varied, showing that the extraction methods interfered with polymer properties. The composition of polyhydroxyalkanoates was also influenced by the extraction, with varying percentages of monomers identified. The copolymers of the polyhydroxyalkanoates obtained are formed by the monomers 11-hydroxyhexadecanoate, in a higher proportion, hydroxyheptanoate and hydroxytetradecanoate, demonstrating that Spirulina sp. LEB-18 is capable of producing medium and long chain polymers. The detection of these monomer blocks in the polyhydroxyalkanoate structure of this microalga is an important scientific novelty because these monomer blocks are constituents of new polymers. An indirect relationship (R2 = 0.8044) was observed between the percentage of the 11-hydroxyhexadecanoate monomer and the degree of crystallinity of polyhydroxyalkanoates obtained by the different methods. This suggests that obtaining the polymer with medium- and long-chain monomers contributes to reduction of crystallinity.

      PubDate: 2018-05-29T04:18:03Z
      DOI: 10.1016/j.ijbiomac.2018.05.064
      Issue No: Vol. 116 (2018)
       
  • Chloroplast engineering of Chlamydomonas reinhardtii to use phosphite as
           phosphorus source
    • Abstract: Publication date: July 2018
      Source:Algal Research, Volume 33
      Author(s): José M. Sandoval-Vargas, Karla S. Macedo-Osorio, Noé V. Durán-Figueroa, Claudio Garibay-Orijel, Jesús A. Badillo-Corona
      Phosphorus (P) is a key biological element and a limiting nutrient in aquatic and terrestrial environments. The vast majority of organisms can only uptake phosphorus in its most oxidized form, as phosphate (PO4 3−), whereas a few prokaryotic species can metabolize phosphorus in a more reduced state such as phosphite (PO3 3−). Recently, it has been shown that by expressing the ptxD gene, encoding a NAD-dependent phosphite dehydrogenase (also known as phosphonate dehydrogenase), in Chlamydomonas reinhardtii phosphite utilization can be enabled. However, this was done by transforming the nuclear genome, where gene silencing is frequent and random integration of transgenes can result in variable levels of gene expression and pleiotropic effects. The aim of this work was to investigate if phosphite assimilation in the eukaryotic algae Chlamydomonas reinhardtii can also be achieved by expressing a codon-optimized ptxD gene in the chloroplast. To do this, the ptxD gene was targeted and stably integrated into the psbA exon 5-5S rRNA intergenic region within the inverted repeats of the C. reinhardtii chloroplast genome. Integration was shown to occur in the targeted site and transplastomic lines were shown to be homoplasmic and to stably accumulate the NAD-dependent phosphite dehydrogenase PTXD, enabling the cells to use phosphite as the sole phosphorus source in a 0.1–5 mM concentration range. This work demonstrates that transplastomic lines of C. reinhardtii expressing the prokaryotic ptxD gene can effectively be cultivated in phosphite, opening new opportunities for microalgae cultivation.

      PubDate: 2018-06-13T05:44:54Z
       
  • Zinc removal by Chlorella sp. biomass and harvesting with low cost
           magnetic particles
    • Authors: Gisela Ferraro; Regina Toranzo Delfina Castiglioni Enio Lima Marcelo Vasquez
      Abstract: Publication date: July 2018
      Source:Algal Research, Volume 33
      Author(s): Gisela Ferraro, Regina M. Toranzo, Delfina M. Castiglioni, Enio Lima, Marcelo Vasquez Mansilla, Nicolas A. Fellenz, Roberto D. Zysler, Daniel M. Pasquevich, Carolina Bagnato
      Remediation of an environment affected by metals based on the use of algae is an important technological breakthrough, where biomass harvesting is the limiting key-point. In this research, iron oxide particles (IOPs) and natural magnetic clay (NMC) coated with polyethilenimine (PEI) were successfully applied in the harvesting of Chlorella sp. coupled to the remediation of zinc ions with harvesting efficiencies >94%. Even though the presence of the metal did not affect the harvesting process, adding IOPs induced a metal displacement which increased zinc concentration upon harvesting. Contrary to that, Clay-PEI functionalized (NMCP) particles increased the amount of removed metal after harvesting. From these results it can be concluded that both tested particles are suitable for harvesting algal biomass and only NMCP are compatible with metal remediation.

      PubDate: 2018-06-07T05:10:31Z
       
  • Growth of microalgae using nitrate-rich brine wash from the water industry
    • Authors: Christian J.A.; Ridley Brenda Parker Louisa Norman Beatrix Schlarb-Ridley Ross
      Abstract: Publication date: July 2018
      Source:Algal Research, Volume 33
      Author(s): Christian J.A. Ridley, Brenda M. Parker, Louisa Norman, Beatrix Schlarb-Ridley, Ross Dennis, Alexandra E. Jamieson, Daniel Clark, Stephen C. Skill, Alison G. Smith, Matthew P. Davey
      Safe and accepted limits for nitrates in drinking water are exceeded in around one-third of the groundwater bodies in Europe. Whilst anion exchange (AEX) is an effective technology to strip nitrates, the regeneration of AEX resins using saturated sodium chloride (brine) results in a significant quantity of nitrate-rich saline waste, which is currently disposed of at a substantial cost to the water industry. The aim of this research was to evaluate the viability of using AEX brine wash as a nutrient source to support microalgal growth. Experiments were carried out at laboratory and pilot scales to test which algal species were able to grow on brine wash, to determine the optimal nitrate concentration within modified growth media, and to identify whether the origin of the brine wash affected the nitrate uptake potential. In small scale laboratory experiments, five marine algal species were able to grow in modified f/2 growth media containing nitrate sourced from the brine wash. Further experiments showed that three species could grow on the modified media at nitrate concentrations from 5 to 274 mg L−1. P. tricornutum could remediate up to 6.5 mg nitrate in 50 mL cultures in laboratory scale experiments, up to 570 mg at 10 L scale and 1700 mg at 100 L scale. We found that the origin of the brine wash did not significantly affect the growth of the cultures or the amount of nitrate removal from the modified media. The algal biomass could be used effectively in biogas production in small-scale trials, although with <10% the yield from P. tricornutum biomass from standard f/2 medium. Our results suggest that it may be possible to derive value from brine wash as a sustainable source of nitrate for the growth of microalgae in bulk after optimisation.

      PubDate: 2018-05-29T04:18:03Z
       
  • Effect of continuous and daytime mixing on Nannochloropsis growth in
           raceway ponds
    • Authors: Ashiwin Vadiveloo; Navid Moheimani
      Abstract: Publication date: July 2018
      Source:Algal Research, Volume 33
      Author(s): Ashiwin Vadiveloo, Navid Moheimani
      Turbulence mixing is critical for generating high microalgal biomass productivity. Mixing also represents a major operational cost in large-scale microalgal production. The integration of photovoltaic cells with microalgae cultivation systems has been shown to eliminate the requirement of conventional grid-supplied electricity in rural areas. However, through such systems, the availability of electricity and the operation of equipment would solely depend on available sunlight and limited to only daytime. In accordance, in this study, we evaluated the effect of continuous paddle wheel mixing (24 h) and daytime mixing (12 h) on the growth, productivity and photosynthesis of Nannochloropsis sp. grown in outdoor paddle wheel driven raceway ponds operated at different depths (15 and 25 cm). Specific growth rates, volumetric and aerial biomass productivities were found to be significantly higher in ponds with 24 hour mixing compared to ponds with only 12 hour mixing operated at the same depth. The depth of the cultures did not affect the growth rate and volumetric productivity of cultures in both mixing conditions. Photosynthetic performance of cultures evaluated through chlorophyll a fluorescence measurements of photosystem II trended higher in ponds with 24 hour mixing compared to ponds subjected to 12 hour mixing. Our results clearly indicate the importance of continuous mixing to achieve high biomass productivity in cultures of Nannochloropsis sp.

      PubDate: 2018-05-29T04:18:03Z
       
  • Product characterization of multi-temperature steps of hydrothermal
           liquefaction of Chlorella microalgae
    • Authors: Zhen Donghai; Liang Liu Yang Wang Shuzhong Wang Yang Guo
      Abstract: Publication date: July 2018
      Source:Algal Research, Volume 33
      Author(s): Zhen He, Donghai Xu, Liang Liu, Yang Wang, Shuzhong Wang, Yang Guo, Zefeng Jing
      Hydrothermal liquefaction (HTL) is a promising technique for crude bio-oil (biocrude) production from microalgae. Instead of traditional direct HTL at one temperature with a residence time, the present work explored two temperature steps (TTS) and more temperature steps (MTS) of microalgae (Chlorella) HTLs for the first time in mini-batch reactors. Specifically, the reactions for the TTS of HTL were performed at a relatively low temperature (150–300 °C) for 10–40 min and then at a high temperature (350 °C) for 10–20 min. In the MTS of HTL, three or four temperature steps were adopted and each temperature stage (within 150–300 °C) was kept for 10 min. The results show that the low temperature pre-reaction stage significantly affected the yield, elemental composition, higher heating value, energy recovery and molecular component of biocrude. The biocrude derived from the TTS of HTL of 250*20–350 (i.e., a pre-reaction at 250 °C for 20 min followed by a HTL at 350 °C for 10 min) had the highest H content (9.00 wt%) and the lowest S content (0.55 wt%). Its yield, elemental composition, higher heating value, and energy recovery were comparable with those of the biocrude from the direct HTL at 350 °C for 30 min (with the highest yield and the best quality in tests). In comparison to direct HTL, a proper TTS of microalgae HTL was able to reduce reaction temperature on the premise of ensuring similar biocrude properties, so might be applicable in the algal bio-oil production.

      PubDate: 2018-05-29T04:18:03Z
       
  • Mechanistic kinetic models describing impact of early attachment between
           Chlorella vulgaris and polyurethane foam material in fluidized bed
           bioreactor on lipid for biodiesel production
    • Authors: Ainur-Assyakirin Mohd-Sahib; Jun-Wei Lim Man-Kee Lam Yoshimitsu Uemura Chii-Dong Wen-Da
      Abstract: Publication date: July 2018
      Source:Algal Research, Volume 33
      Author(s): Ainur-Assyakirin Mohd-Sahib, Jun-Wei Lim, Man-Kee Lam, Yoshimitsu Uemura, Chii-Dong Ho, Wen-Da Oh, Wen-Nee Tan
      The fundamental mechanism of early attachment between Chlorella vulgaris microalgae cells and polyurethane foam support material was unveiled prior to the kinetic study and optimization of operational bed packing volume in fluidized bed bioreactor. All aiming to enhance the lipid accumulation for sustainable biodiesel production. The two-step early attachment mechanism was found starting with the short-range Lewis acid-base interaction before the cells migrating toward the surface of support material induced by the electrostatic attractive force. This mechanism was mainly propelled by the chemisorption stemming from the interactions of cell-to-cell repulsion and cell-to-support material attraction. The electrostatic attractive interaction transpired on the surface of support material was also maneuvering the kinetics of formation of early attachment as reflected by the zeta potential trend via the sequence of pH 9 < pH 7 < pH 5 > pH 3. The rapid early attachment formation in pH 5 culture medium in fluidized bed bioreactor had led to the highest weight of attached growth microalgae biomass attainability as opposed to the other pH mediums. By exploiting the pH 5 culture medium, the maximum yields of microalgae biomass, lipid and later biodiesel were harvested from the bioreactor packed with 6% (v/v) of polyurethane foam support material, confirming optimum packing volume. These yields were initially observed increasing with the increase of packing volume due to the increasing surface area of support material; and unfortunately, decreasing after 6% (v/v) of packing volume due to the congestion factor.
      Graphical abstract image

      PubDate: 2018-05-29T04:18:03Z
       
  • Impact of thiamine metabolites and spent medium from Chlorella sorokiniana
           on metabolism in the green algae Auxenochlorella prototheciodes
    • Authors: Brendan Higgins; Qichen Wang Sandon Marie Hennebelle Ameer Taha Oliver
      Abstract: Publication date: July 2018
      Source:Algal Research, Volume 33
      Author(s): Brendan T. Higgins, Qichen Wang, Sandon Du, Marie Hennebelle, Ameer Y. Taha, Oliver Fiehn, Jean S. VanderGheynst
      Auxenochlorella protothecoides is a known thiamine auxotroph but our past work has shown that it can synthesize thiamine if provided with the precursor molecule 4-amino-5-hydroxymethyl-2-methylpyrimidine (HMP). Partial thiamine auxotrophy is common in microalgae with important ramifications for global phytoplankton productivity as well as engineering applications of algae. While thiamine deficiency can greatly depress algae growth and lipid content, the detailed metabolic impacts of thiamine deficiency are not well understood. We used metabolomics to study the response to thiamine-limited and replete conditions in mixotrophic A. protothecoides. We also investigated the impacts of exogenous HMP addition and the use of spent medium from another green algae, C. sorokiniana, as a source of thiamine metabolites. This is the first study, to our knowledge, that addresses metabolic impacts of thiamine deficiency and alleviation in green microalgae. Thiamine deficient cultures exhibited accumulation of pyruvate and α-ketoglutarate, indicating bottlenecks at the pyruvate dehydrogenase (PDH) and oxoglutarate dehydrogenase (OGDH) complexes. Both PDH and OGDH require thiamine pyrophosphate (TPP) as a cofactor. Transketolase also requires TPP but we only observed build-up of ribose-5-phosphate when glucose was supplied as a substrate. As expected, thiamine and HMP addition could alleviate these metabolic bottlenecks while greatly increasing algal growth, neutral lipid and starch content. Spent medium from C. sorokiniana only appeared to partially alleviate thiamine deficiency and resulted in build-up of isocitrate and glycolate, metabolites that appeared relatively unaffected by the presence or absence of thiamine. Interestingly, longer culture time of C. sorokiniana when preparing the spent medium led to much higher availability of thiamine metabolites. Thus, under the right conditions, it may be possible to co-culture mutually beneficial algae species and/or recycle spent cultivation medium to overcome auxotrophy in algae.

      PubDate: 2018-05-29T04:18:03Z
       
  • Polymer accumulation in mixed cyanobacterial cultures selected under the
           feast and famine strategy
    • Authors: Dulce Arias; Joana Fradinho Enrica Uggetti Joan Adrian Oehmen Maria
      Abstract: Publication date: July 2018
      Source:Algal Research, Volume 33
      Author(s): Dulce María Arias, Joana C. Fradinho, Enrica Uggetti, Joan García, Adrian Oehmen, Maria A.M. Reis
      In this study, a sequencing batch reactor (SBR), operated with transient carbon availability (feast and famine) and different nutrients loads, was used to select cyanobacteria accumulating poly (3-hydroxyalkanoate) (PHB) and carbohydrates from a mixed wastewater-borne microbial culture. The SBR was operated with 12 h aerobic light and 12 h anaerobic dark phases, evaluating the effect of three different operational conditions consisting on; 1) carbon limitation, 2) carbon and phosphorus limitation and 3) phosphorus limitation. Once a steady state was reached in each operational period of the SBR, part of the biomass was collected and submitted to separate batch tests in order to investigate the maximum PHB and carbohydrates accumulation levels. Batch tests were performed during 24 h of illuminated aerobic condition and 24 h of dark anaerobic condition, while inorganic carbon was constantly present. During the SBR operation, inorganic carbon was mostly used for biomass and carbohydrate production, showing very low PHB accumulation levels (<1%). Notwithstanding, in subsequent batch tests, PHB was accumulated after a complete depletion of nitrogen, reaching almost 4%. Concerning carbohydrates, it was found that phosphorus limitation (with and without carbon limitation) led to a culture mostly dominated by cyanobacteria and higher levels of carbohydrate content (43%–48%) than the culture with carbon limitation and high loads of nitrogen and phosphorus (29%). Such contents were obtained in only 24 h of incubation under aerobic illuminated conditions. Hence, these encouraging results indicate that carbon uptake and the consequent polymers production from cyanobacteria can be enhanced through carbon and nutrient feeding strategies.

      PubDate: 2018-05-29T04:18:03Z
       
  • Inside Front Cover - Editorial Board Page/Cover image legend if applicable
    • Abstract: Publication date: June 2018
      Source:Algal Research, Volume 32


      PubDate: 2018-05-29T04:18:03Z
       
 
 
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