Microalgal Biotechnology

A special issue of Biology (ISSN 2079-7737).

Deadline for manuscript submissions: closed (31 March 2018) | Viewed by 138047

Special Issue Editors


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Guest Editor
Institute of Structural and Molecular Biology, Darwin Building, University College London, Gower Street, London WC1E 6BT, UK
Interests: algal biotechnology; synthetic biology; chloroplast genetic engineering; oral vaccines and anti-microbials; photosynthesis
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Guest Editor
Department of Biochemical Engineering, University College London, London, UK
Interests: microalgal bioprocessing; industrial biotechnology; biocatalysis; bioremediation

Special Issue Information

Dear Colleagues,

There is a growing interest in the opportunities that microalgae and cyanobacteria offer in industrial biotechnology as light-driven platforms for the production of valuable bio-products. These range from bulk products such as biofuels and animal feeds to high-value compounds for the cosmetics, nutraceutical and pharmaceutical sectors. The extreme diversity amongst these phototrophic microorganisms provides a rich vein of novel compounds and biochemical pathways, although such bioprospecting is still in its infancy. Furthermore, the development of genetic engineering technologies for various platform species opens the door to domesticated or ‘designer’ strains with enhanced productivity of natural compounds, or low-cost synthesis of recombinant products including therapeutic proteins or bioactive metabolites. This special issue invites original research papers and reviews that cover all aspects of the field — from strain characterization and genetic enhancement, to cultivation technologies and downstream processing.

Prof. Saul Purton
Dr. Brenda Parker
Guest Editors

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Keywords

  • Algal biofuels

  • Algal synthetic biology

  • Bioactives from microalgae

  • Bioprospecting novel algal species

  • Cyanobacterial biotechnology

  • Genetic engineering of algae

  • Photobioreactor design and operation

Published Papers (15 papers)

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Research

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14 pages, 1419 KiB  
Article
Expression of a Synthetic Gene for the Major Cytotoxin (Cyt1Aa) of Bacillus thuringiensis subsp. israelensis in the Chloroplast of Wild-Type Chlamydomonas
by Seongjoon Kang, Obed W. Odom, Candice L. Malone, Saravanan Thangamani and David L. Herrin
Biology 2018, 7(2), 29; https://doi.org/10.3390/biology7020029 - 8 May 2018
Cited by 8 | Viewed by 5091
Abstract
Chlamydomonas reinhardtii (Chlamydomonas) strains that are toxic to mosquito larvae because they express chloroplast transgenes that are based on the mosquitocidal proteins of Bacillus thuringiensis subsp. israelensis (Bti) could be very useful in mosquito control. Chlamydomonas has several advantages for this [...] Read more.
Chlamydomonas reinhardtii (Chlamydomonas) strains that are toxic to mosquito larvae because they express chloroplast transgenes that are based on the mosquitocidal proteins of Bacillus thuringiensis subsp. israelensis (Bti) could be very useful in mosquito control. Chlamydomonas has several advantages for this approach, including genetic controls not generally available with industrial algae. The Bti toxin is produced by sporulating bacteria and has been used for mosquito control for >30 years without creating highly resistant mosquito populations. The suite of toxins is four main proteins: three Cry proteins and the cytotoxic Cyt1Aa (27 kDa). Cyt1Aa is not very toxic to mosquitoes by itself, but it prevents the development of resistance. The production of Cyt1Aa in other microbes, however, has been challenging due to its affinity for certain membrane phospholipids. Here we report on the production of recombinant Cyt1Aa (rCyt1A) in the chloroplast of photosynthetic Chlamydomonas at levels of at least 0.3% total protein. Live cell bioassays demonstrated toxicity of the rCyt1Aa Chlamydomonas to larvae of Aedes aegypti. We also expressed the chloroplast cyt1Aa gene in a wild-type Chlamydomonas strain (21 gr) that can grow on nitrate. These results have implications for developing a Chlamydomonas strain that will be toxic to mosquito larvae but will not induce strongly resistant populations. Full article
(This article belongs to the Special Issue Microalgal Biotechnology)
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12 pages, 10998 KiB  
Article
Electrochemical Characterisation of Bio-Bottle-Voltaic (BBV) Systems Operated with Algae and Built with Recycled Materials
by Peter Bateson, Jack E. H. Fleet, Anthony S. Riseley, Elena Janeva, Anastasia S. Marcella, Chiara Farinea, Maria Kuptsova, Núria Conde Pueyo, Christopher J. Howe, Paolo Bombelli and Brenda M. Parker
Biology 2018, 7(2), 26; https://doi.org/10.3390/biology7020026 - 17 Apr 2018
Cited by 15 | Viewed by 9957
Abstract
Photobioelectrochemical systems are an emerging possibility for renewable energy. By exploiting photosynthesis, they transform the energy of light into electricity. This study evaluates a simple, scalable bioelectrochemical system built from recycled plastic bottles, equipped with an anode made from recycled aluminum, and operated [...] Read more.
Photobioelectrochemical systems are an emerging possibility for renewable energy. By exploiting photosynthesis, they transform the energy of light into electricity. This study evaluates a simple, scalable bioelectrochemical system built from recycled plastic bottles, equipped with an anode made from recycled aluminum, and operated with the green alga Chlorella sorokiniana. We tested whether such a system, referred to as a bio-bottle-voltaic (BBV) device, could operate outdoors for a prolonged time period of 35 days. Electrochemical characterisation was conducted by measuring the drop in potential between the anode and the cathode, and this value was used to calculate the rate of charge accumulation. The BBV systems were initially able to deliver ~500 mC·bottle−1·day−1, which increased throughout the experimental run to a maximum of ~2000 mC·bottle−1·day−1. The electrical output was consistently and significantly higher than that of the abiotic BBV system operated without algal cells (~100 mC·bottle−1·day−1). The analysis of the rate of algal biomass accumulation supported the hypothesis that harvesting a proportion of electrons from the algal cells does not significantly perturb the rate of algal growth. Our finding demonstrates that bioelectrochemical systems can be built using recycled components. Prototypes of these systems have been displayed in public events; they could serve as educational toolkits in schools and could also offer a solution for powering low-energy devices off-grid. Full article
(This article belongs to the Special Issue Microalgal Biotechnology)
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12 pages, 4665 KiB  
Article
Characterization of Chlorella sorokiniana, UTEX 1230
by Alessandro Marco Lizzul, Aitor Lekuona-Amundarain, Saul Purton and Luiza Cintra Campos
Biology 2018, 7(2), 25; https://doi.org/10.3390/biology7020025 - 13 Apr 2018
Cited by 57 | Viewed by 9277
Abstract
This paper characterizes the strain Chlorella sorokiniana UTEX 1230 within a laboratory setting using a 1 L bubble column. The findings show that productivity can be trebled under mixotrophic conditions (from 0.2 g·L−1·d−1 to 0.66 g·L−1·d−1) [...] Read more.
This paper characterizes the strain Chlorella sorokiniana UTEX 1230 within a laboratory setting using a 1 L bubble column. The findings show that productivity can be trebled under mixotrophic conditions (from 0.2 g·L−1·d−1 to 0.66 g·L−1·d−1) with the addition of sodium acetate. The results also indicate that both the growth rate and final yield increase with the cultivation temperature, with most parameters showing an optimum in the range of 30–35 °C. The maximum specific growth rate was found to be in the region of 0.12 h−1 at a surface irradiance between 100–500 µE·m−2·s−1. This high growth rate makes the strain particularly suited to the rapid production of biomass, suitable for either whole cell bioprocessing or bioremediation. However, the relatively low lipid productivity (9.2 mg·L−1·d−1) confirms previous findings which would indicate poor applicability for biodiesel production. The strain shows greater promise in wastewater treatment applications with removal rates of nitrogen and phosphorus in the region of 37 and 30 mg·L−1·d−1 respectively. Furthermore, the findings show that a fed-batch strategy to inorganic nutrient loading can increase the final yield by around 50% compared to a conventional batch run. This is particularly interesting as fed-batch production techniques are rarely used within microalgal cultivation, so provide an interesting avenue for further investigation. Overall, the findings show that C. sorokiniana UTEX 1230 is a robust and fast-growing microalgal strain suitable both for the laboratory and scale-up. Full article
(This article belongs to the Special Issue Microalgal Biotechnology)
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13 pages, 1329 KiB  
Article
Human Intrinsic Factor Expression for Bioavailable Vitamin B12 Enrichment in Microalgae
by Serena Lima, Conner L. Webb, Evelyne Deery, Colin Robinson and Julie A. Z. Zedler
Biology 2018, 7(1), 19; https://doi.org/10.3390/biology7010019 - 19 Feb 2018
Cited by 11 | Viewed by 6478
Abstract
Dietary supplements and functional foods are becoming increasingly popular complements to regular diets. A recurring ingredient is the essential cofactor vitamin B12 (B12). Microalgae are making their way into the dietary supplement and functional food market but do not produce [...] Read more.
Dietary supplements and functional foods are becoming increasingly popular complements to regular diets. A recurring ingredient is the essential cofactor vitamin B12 (B12). Microalgae are making their way into the dietary supplement and functional food market but do not produce B12, and their B12 content is very variable. In this study, the suitability of using the human B12-binding protein intrinsic factor (IF) to enrich bioavailable B12 using microalgae was tested. The IF protein was successfully expressed from the nuclear genome of the model microalga Chlamydomonas reinhardtii and the addition of an N-terminal ARS2 signal peptide resulted in efficient IF secretion to the medium. Co-abundance of B12 and the secreted IF suggests the algal produced IF protein is functional and B12-binding. Utilizing IF expression could be an efficient tool to generate B12-enriched microalgae in a controlled manner that is suitable for vegetarians and, potentially, more bioavailable for humans. Full article
(This article belongs to the Special Issue Microalgal Biotechnology)
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14 pages, 2429 KiB  
Article
Detection and Enhancement of Ketocarotenoid Accumulation in the Newly Isolated Sarcinoid Green Microalga Chlorosarcinopsis PY02
by Peelada Cherdchukeattisak, Paul D. Fraser, Saul Purton and Thanyanan Wannathong Brocklehurst
Biology 2018, 7(1), 17; https://doi.org/10.3390/biology7010017 - 12 Feb 2018
Cited by 5 | Viewed by 6409
Abstract
The sarcinoid alga PY02 is a newly isolated soil alga native to western Thailand. In this study PY02 is described, the carotenoid profile of the green and red forms of the algal cells are compared, and the effect of nitrogen reduction and media [...] Read more.
The sarcinoid alga PY02 is a newly isolated soil alga native to western Thailand. In this study PY02 is described, the carotenoid profile of the green and red forms of the algal cells are compared, and the effect of nitrogen reduction and media volume on ketocarotenoid production are reported. Partial sequences of the genes from elongation factor Tu (tufA) and 18S rRNA reveal that the alga is from the Chlorosarcinopsis genus. Growth studies demonstrated that Chlorosarcinopsis PY02 is capable of photoautotrophic, heterotrophic and mixotrophic growth. A gradual change in colony colour from green to red was observed over a period of four weeks under mixotrophic conditions. Pigment analysis of lyophilized red cells using ultrahigh performance liquid chromatography (UPLC) with Photo Diode Array Detection (PDA), showed for the first time that an alga from the genus Chlorosarcinopsis is capable of producing ketocarotenoids such as adonixanthin and 3-OH-echinenone, with canthaxanthin as the dominant pigment. Interestingly, a reduction of nitrogen in the medium exerts a positive effect on the rate of colour change from one month to less than seven days. Enhancements of the canthaxanthin content from 520 to 1504 or 1427 µg·gDW−1 were detected under 50% and 10% nitrogen content, respectively. An increase of 16% in biomass production of PY02 was unexpectedly detected from a 50% nitrogen reduction under mixotrophic culture. Notably, in liquid mixotrophic media with volumes of 15, 30 and 60 mL, the lowest volume produced a significantly higher biomass and canthaxanthin content. Full article
(This article belongs to the Special Issue Microalgal Biotechnology)
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18 pages, 5199 KiB  
Article
Potential of New Isolates of Dunaliella Salina for Natural β-Carotene Production
by Yanan Xu, Iskander M. Ibrahim, Chiziezi I. Wosu, Ami Ben-Amotz and Patricia J. Harvey
Biology 2018, 7(1), 14; https://doi.org/10.3390/biology7010014 - 1 Feb 2018
Cited by 89 | Viewed by 11081
Abstract
The halotolerant microalga Dunaliella salina has been widely studied for natural β-carotene production. This work shows biochemical characterization of three newly isolated Dunaliella salina strains, DF15, DF17, and DF40, compared with D. salina CCAP 19/30 and D. salina UTEX 2538 (also known as [...] Read more.
The halotolerant microalga Dunaliella salina has been widely studied for natural β-carotene production. This work shows biochemical characterization of three newly isolated Dunaliella salina strains, DF15, DF17, and DF40, compared with D. salina CCAP 19/30 and D. salina UTEX 2538 (also known as D. bardawil). Although all three new strains have been genetically characterized as Dunaliella salina strains, their ability to accumulate carotenoids and their capacity for photoprotection against high light stress are different. DF15 and UTEX 2538 reveal great potential for producing a large amount of β-carotene and maintained a high rate of photosynthesis under light of high intensity; however, DF17, DF40, and CCAP 19/30 showed increasing photoinhibition with increasing light intensity, and reduced contents of carotenoids, in particular β-carotene, suggesting that the capacity of photoprotection is dependent on the cellular content of carotenoids, in particular β-carotene. Strong positive correlations were found between the cellular content of all-trans β-carotene, 9-cis β-carotene, all-trans α-carotene and zeaxanthin but not lutein in the D. salina strains. Lutein was strongly correlated with respiration in photosynthetic cells and strongly related to photosynthesis, chlorophyll and respiration, suggesting an important and not hitherto identified role for lutein in coordinated control of the cellular functions of photosynthesis and respiration in response to changes in light conditions, which is broadly conserved in Dunaliella strains. Statistical analysis based on biochemical data revealed a different grouping strategy from the genetic classification of the strains. The significance of these data for strain selection for commercial carotenoid production is discussed. Full article
(This article belongs to the Special Issue Microalgal Biotechnology)
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21 pages, 5378 KiB  
Article
Comparing Nutrient Removal from Membrane Filtered and Unfiltered Domestic Wastewater Using Chlorella vulgaris
by Elyssia Mayhead, Alla Silkina, Carole A. Llewellyn and Claudio Fuentes-Grünewald
Biology 2018, 7(1), 12; https://doi.org/10.3390/biology7010012 - 19 Jan 2018
Cited by 32 | Viewed by 8418
Abstract
The nutrient removal efficiency of Chlorella vulgaris cultivated in domestic wastewater was investigated, along with the potential to use membrane filtration as a pre-treatment tool during the wastewater treatment process. Chlorella vulgaris was batch cultivated for 12 days in a bubble column system [...] Read more.
The nutrient removal efficiency of Chlorella vulgaris cultivated in domestic wastewater was investigated, along with the potential to use membrane filtration as a pre-treatment tool during the wastewater treatment process. Chlorella vulgaris was batch cultivated for 12 days in a bubble column system with two different wastewater treatments. Maximum uptake of 94.18% ammonium (NH4-N) and 97.69% ortho-phosphate (PO4-P) occurred in 0.2 μm membrane filtered primary wastewater. Membrane filtration enhanced the nutrient uptake performance of C. vulgaris by removing bacteria, protozoa, colloidal particles and suspended solids, thereby improving light availability for photosynthesis. The results of this study suggest that growing C. vulgaris in nutrient rich membrane filtered wastewater provides an option for domestic wastewater treatment to improve the quality of the final effluent. Full article
(This article belongs to the Special Issue Microalgal Biotechnology)
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2545 KiB  
Article
Harvesting Environmental Microalgal Blooms for Remediation and Resource Recovery: A Laboratory Scale Investigation with Economic and Microbial Community Impact Assessment
by Jagroop Pandhal, Wai L. Choon, Rahul V. Kapoore, David A. Russo, James Hanotu, I. A. Grant Wilson, Pratik Desai, Malcolm Bailey, William J. Zimmerman and Andrew S. Ferguson
Biology 2018, 7(1), 4; https://doi.org/10.3390/biology7010004 - 29 Dec 2017
Cited by 15 | Viewed by 6161
Abstract
A laboratory based microflotation rig termed efficient FLOtation of Algae Technology (eFLOAT) was used to optimise parameters for harvesting microalgal biomass from eutrophic water systems. This was performed for the dual objectives of remediation (nutrient removal) and resource recovery. Preliminary experiments demonstrated that [...] Read more.
A laboratory based microflotation rig termed efficient FLOtation of Algae Technology (eFLOAT) was used to optimise parameters for harvesting microalgal biomass from eutrophic water systems. This was performed for the dual objectives of remediation (nutrient removal) and resource recovery. Preliminary experiments demonstrated that chitosan was more efficient than alum for flocculation of biomass and the presence of bacteria could play a positive role and reduce flocculant application rates under the natural conditions tested. Maximum biomass removal from a hyper-eutrophic water retention pond sample was achieved with 5 mg·L−1 chitosan (90% Chlorophyll a removal). Harvesting at maximum rates showed that after 10 days, the bacterial diversity is significantly increased with reduced cyanobacteria, indicating improved ecosystem functioning. The resource potential within the biomass was characterized by 9.02 μg phosphate, 0.36 mg protein, and 103.7 μg lipid per mg of biomass. Fatty acid methyl ester composition was comparable to pure cultures of microalgae, dominated by C16 and C18 chain lengths with saturated, monounsaturated, and polyunsaturated fatty acids. Finally, the laboratory data was translated into a full-size and modular eFLOAT system, with estimated costs as a novel eco-technology for efficient algal bloom harvesting. Full article
(This article belongs to the Special Issue Microalgal Biotechnology)
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1767 KiB  
Article
Media Screening for Obtaining Haematococcus pluvialis Red Motile Macrozooids Rich in Astaxanthin and Fatty Acids
by Thomas O. Butler, Gordon J. McDougall, Raymond Campbell, Michele S. Stanley and John G. Day
Biology 2018, 7(1), 2; https://doi.org/10.3390/biology7010002 - 26 Dec 2017
Cited by 59 | Viewed by 9513
Abstract
Astaxanthin from Haematococcus pluvialis is commercially produced in a two-stage process, involving green vegetative (macrozooid) and red aplanospore stages. This approach has been scaled up to an industrial process but constraints limit its commercial success and profitability, including: contamination issues, high pigment extraction [...] Read more.
Astaxanthin from Haematococcus pluvialis is commercially produced in a two-stage process, involving green vegetative (macrozooid) and red aplanospore stages. This approach has been scaled up to an industrial process but constraints limit its commercial success and profitability, including: contamination issues, high pigment extraction costs, requirements for high light levels and photo-bleaching in the red stage. However, in addition to the aplanospore stage, this alga can produce astaxanthin in vegetative palmelloid and motile macrozooid cells. In this study, a two-stage process utilising different media in the green stage, with subsequent re-suspension in medium without nitrate was employed to optimise the formation of red motile macrozooids. Optimal growth in the green phase was obtained on cultivation under mixotrophic conditions in EG:JM media followed by re-suspension in medium without nitrate resulting in red motile macrozooids with an astaxanthin content of 2.74% (78.4% of total carotenoids) and a lipid content of 35.3% (rich in unsaturated fatty acids. It is envisaged that the red motile macrozooids could be harvested and fed as a whole-cell product directly in the animal feed and aquaculture sectors, or used as a blend of carotenoids and polyunsaturated fatty acids (PUFAs) in nutraceutical products. Full article
(This article belongs to the Special Issue Microalgal Biotechnology)
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3323 KiB  
Article
Exploring the Glycans of Euglena gracilis
by Ellis C. O’Neill, Sakonwan Kuhaudomlarp, Martin Rejzek, Jonatan U. Fangel, Kathirvel Alagesan, Daniel Kolarich, William G. T. Willats and Robert A. Field
Biology 2017, 6(4), 45; https://doi.org/10.3390/biology6040045 - 15 Dec 2017
Cited by 31 | Viewed by 7168
Abstract
Euglena gracilis is an alga of great biotechnological interest and extensive metabolic capacity, able to make high levels of bioactive compounds, such as polyunsaturated fatty acids, vitamins and β-glucan. Previous work has shown that Euglena expresses a wide range of carbohydrate-active enzymes, suggesting [...] Read more.
Euglena gracilis is an alga of great biotechnological interest and extensive metabolic capacity, able to make high levels of bioactive compounds, such as polyunsaturated fatty acids, vitamins and β-glucan. Previous work has shown that Euglena expresses a wide range of carbohydrate-active enzymes, suggesting an unexpectedly high capacity for the synthesis of complex carbohydrates for a single-celled organism. Here, we present an analysis of some of the carbohydrates synthesised by Euglena gracilis. Analysis of the sugar nucleotide pool showed that there are the substrates necessary for synthesis of complex polysaccharides, including the unusual sugar galactofuranose. Lectin- and antibody-based profiling of whole cells and extracted carbohydrates revealed a complex galactan, xylan and aminosugar based surface. Protein N-glycan profiling, however, indicated that just simple high mannose-type glycans are present and that they are partially modified with putative aminoethylphosphonate moieties. Together, these data indicate that Euglena possesses a complex glycan surface, unrelated to plant cell walls, while its protein glycosylation is simple. Taken together, these findings suggest that Euglena gracilis may lend itself to the production of pharmaceutical glycoproteins. Full article
(This article belongs to the Special Issue Microalgal Biotechnology)
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Review

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26 pages, 2808 KiB  
Review
Selectable Markers and Reporter Genes for Engineering the Chloroplast of Chlamydomonas reinhardtii
by Lola Esland, Marco Larrea-Alvarez and Saul Purton
Biology 2018, 7(4), 46; https://doi.org/10.3390/biology7040046 - 10 Oct 2018
Cited by 37 | Viewed by 14848
Abstract
Chlamydomonas reinhardtii is a model alga of increasing interest as a cell factory for the production of valuable compounds, including therapeutic proteins and bioactive metabolites. Expression of foreign genes in the chloroplast is particularly advantageous as: (i) accumulation of product in this sub-cellular [...] Read more.
Chlamydomonas reinhardtii is a model alga of increasing interest as a cell factory for the production of valuable compounds, including therapeutic proteins and bioactive metabolites. Expression of foreign genes in the chloroplast is particularly advantageous as: (i) accumulation of product in this sub-cellular compartment minimises potential toxicity to the rest of the cell; (ii) genes can integrate at specific loci of the chloroplast genome (plastome) by homologous recombination; (iii) the high ploidy of the plastome and the high-level expression of chloroplast genes can be exploited to achieve levels of recombinant protein as high as 5% total cell protein; (iv) the lack of any gene silencing mechanisms in the chloroplast ensures stable expression of transgenes. However, the generation of C. reinhardtii chloroplast transformants requires efficient methods of selection, and ideally methods for subsequent marker removal. Additionally, the use of reporter genes is critical to achieving a comprehensive understanding of gene expression, thereby informing experimental design for recombinant applications. This review discusses currently available selection and reporter systems for chloroplast engineering in C. reinhardtii, as well as those used for chloroplast engineering in higher plants and other microalgae, and looks to the future in terms of possible new markers and reporters that will further advance the C. reinhardtii chloroplast as an expression platform. Full article
(This article belongs to the Special Issue Microalgal Biotechnology)
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14 pages, 607 KiB  
Review
Applications of Microalgal Biotechnology for Disease Control in Aquaculture
by Patai Charoonnart, Saul Purton and Vanvimon Saksmerprome
Biology 2018, 7(2), 24; https://doi.org/10.3390/biology7020024 - 12 Apr 2018
Cited by 82 | Viewed by 13404
Abstract
Aquaculture industries, and in particular the farming of fish and crustaceans, are major contributors to the economy of many countries and an increasingly important component in global food supply. However, the severe impact of aquatic microbial diseases on production performance remains a challenge [...] Read more.
Aquaculture industries, and in particular the farming of fish and crustaceans, are major contributors to the economy of many countries and an increasingly important component in global food supply. However, the severe impact of aquatic microbial diseases on production performance remains a challenge to these industries. This article considers the potential applications of microalgal technology in the control of such diseases. At the simplest level, microalgae offer health-promoting benefits as a nutritional supplement in feed meal because of their digestibility and high content of proteins, lipids and essential nutrients. Furthermore, some microalgal species possess natural anti-microbial compounds or contain biomolecules that can serve as immunostimulants. In addition, emerging genetic engineering technologies in microalgae offer the possibility of producing ‘functional feed additives’ in which novel and specific bioactives, such as fish growth hormones, anti-bacterials, subunit vaccines, and virus-targeted interfering RNAs, are components of the algal supplement. The evaluation of such technologies for farm applications is an important step in the future development of sustainable aquaculture. Full article
(This article belongs to the Special Issue Microalgal Biotechnology)
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13 pages, 987 KiB  
Review
Gene Editing of Microalgae: Scientific Progress and Regulatory Challenges in Europe
by Andrew Spicer and Attila Molnar
Biology 2018, 7(1), 21; https://doi.org/10.3390/biology7010021 - 6 Mar 2018
Cited by 45 | Viewed by 8663
Abstract
It is abundantly clear that the development of gene editing technologies, represents a potentially powerful force for good with regard to human and animal health and addressing the challenges we continue to face in a growing global population. This now includes the development [...] Read more.
It is abundantly clear that the development of gene editing technologies, represents a potentially powerful force for good with regard to human and animal health and addressing the challenges we continue to face in a growing global population. This now includes the development of approaches to modify microalgal strains for potential improvements in productivity, robustness, harvestability, processability, nutritional composition, and application. The rapid emergence and ongoing developments in this area demand a timely review and revision of the current definitions and regulations around genetically modified organisms (GMOs), particularly within Europe. Current practices within the EU provide exemptions from the GMO directives for organisms, including crop plants and micro-organisms that are produced through chemical or UV/radiation mutagenesis. However, organisms generated through gene editing, including microalgae, where only genetic changes in native genes are made, remain currently under the GMO umbrella; they are, as such, excluded from practical and commercial opportunities in the EU. In this review, we will review the advances that are being made in the area of gene editing in microalgae and the impact of regulation on commercial advances in this area with consideration to the current regulatory framework as it relates to GMOs including GM microalgae in Europe. Full article
(This article belongs to the Special Issue Microalgal Biotechnology)
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25 pages, 910 KiB  
Review
Microwave-Assisted Extraction for Microalgae: From Biofuels to Biorefinery
by Rahul Vijay Kapoore, Thomas O. Butler, Jagroop Pandhal and Seetharaman Vaidyanathan
Biology 2018, 7(1), 18; https://doi.org/10.3390/biology7010018 - 15 Feb 2018
Cited by 157 | Viewed by 14142
Abstract
The commercial reality of bioactive compounds and oil production from microalgal species is constrained by the high cost of production. Downstream processing, which includes harvesting and extraction, can account for 70–80% of the total cost of production. Consequently, from an economic perspective extraction [...] Read more.
The commercial reality of bioactive compounds and oil production from microalgal species is constrained by the high cost of production. Downstream processing, which includes harvesting and extraction, can account for 70–80% of the total cost of production. Consequently, from an economic perspective extraction technologies need to be improved. Microalgal cells are difficult to disrupt due to polymers within their cell wall such as algaenan and sporopollenin. Consequently, solvents and disruption devices are required to obtain products of interest from within the cells. Conventional techniques used for cell disruption and extraction are expensive and are often hindered by low efficiencies. Microwave-assisted extraction offers a possibility for extraction of biochemical components including lipids, pigments, carbohydrates, vitamins and proteins, individually and as part of a biorefinery. Microwave technology has advanced since its use in the 1970s. It can cut down working times and result in higher yields and purity of products. In this review, the ability and challenges in using microwave technology are discussed for the extraction of bioactive products individually and as part of a biorefinery approach. Full article
(This article belongs to the Special Issue Microalgal Biotechnology)
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Other

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13 pages, 3807 KiB  
Discussion
Lipid Production in Nannochloropsis gaditana during Nitrogen Starvation
by Jorijn H. Janssen, René H. Wijffels and Maria J. Barbosa
Biology 2019, 8(1), 5; https://doi.org/10.3390/biology8010005 - 8 Jan 2019
Cited by 27 | Viewed by 5288
Abstract
The microalga Nannochloropsis gaditana is a natural producer of triacylglycerol (TAG) and the omega-3 fatty acid eicosapentaenoic acid (EPA). TAG accumulation is induced by nitrogen starvation. The biomass-specific photon supply rate used had an effect on EPA and TAG accumulation during nitrogen starvation [...] Read more.
The microalga Nannochloropsis gaditana is a natural producer of triacylglycerol (TAG) and the omega-3 fatty acid eicosapentaenoic acid (EPA). TAG accumulation is induced by nitrogen starvation. The biomass-specific photon supply rate used had an effect on EPA and TAG accumulation during nitrogen starvation as well as on the localization of EPA accumulation. Clear differences in TAG yield on light were found for different biomass-specific photon supply rates and light regimes during nitrogen starvation. De novo EPA synthesis or the translocation of EPA between lipid fractions might be limiting for EPA accumulation in TAG. Further studies are needed to fully understand EPA accumulation in TAG during nitrogen starvation. To elucidate the function of EPA in TAG nitrogen recovery, experiments are suggested. The overexpression of genes involved in de novo EPA synthesis and translocation is proposed to elucidate the exact metabolic routes involved in these processes during nitrogen starvation. This work addresses future opportunities to increase EPA accumulation. Full article
(This article belongs to the Special Issue Microalgal Biotechnology)
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