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Marine Thraustochytrids: Biology, Chemical Ecology and Biotechnology

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A special issue of Marine Drugs (ISSN 1660-3397).

Deadline for manuscript submissions: closed (15 April 2022) | Viewed by 19870

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Special Issue Editor

Dr. Alberto Amato

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Guest Editor

Laboratoire de Physiologie Cellulaire et Végétale, IRIG-CEA Grenoble 1è Avenue des Martyrs, CEDEX 9, 38 054 Grenoble, France
Interests: biotechnology; transcriptomics; genomics; lipidomics; microalgae

Special Issue Information

Dear Colleagues,

The marine environment hides precious treasures, and humans have always chased them. Nowadays, the treasures hidden in the oceans are natural molecules such as lipids, carotenoids, and other metabolites.

Thraustochytrids have attracted a great deal of biotechnological interest in the last few decades because of their ability to accumulate large amounts of triacylglycerides (TAGs), i.e., oils, rich in Ω3 very-long-chain polyunsaturated fatty acids (Ω3 PUFAs) and carotenoids. TAGs accumulated by thraustochytrids are peculiar in that they are rich in docosahexaenoic acid (DHA), a fatty acid with a plethora of beneficial effects on human health. DHA is poorly synthesized by animals and the sole source is open-ocean fish oil; however, indiscriminate fishing pressure has dramatically reduced the accessibility to this compound. Indeed, fish oil is rich in Ω3 fatty acids because fish feed on zooplankton, which, in turn, feed on phytoplankton—the only organisms able to synthesize DHA. A shortcut is then possible, producing DHA (and other compounds) directly from algae. In the last few years, green biotechnology is gathering increasing interest, nevertheless our sparse knowledge in microalgal biology and metabolisms hampers a more efficient exploitation of such a valuable resource.

This Special Issue aims to collect papers on thraustochytrid biology, physiology, and chemical ecology, that are related to the biosynthesis and production of bioactive compounds in thraustochytrids, and biotechnology of thraustochytrid (i.e., cultivation of thraustochytrids for polyunsaturated fatty acid bioproduction).

Dr. Alberto Amato
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Marine Drugs is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2900 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

Lipid metabolism
Carotenoids
DHA
Omega-3 very-long-chain polyunsaturated fatty acids
Green biotechnology
Fermentation
Chemical species concept
Marine-derived active molecules

Published Papers (7 papers)

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Research

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19 pages, 4923 KiB

Open AccessArticle

Scale-Up to Pilot of a Non-Axenic Culture of Thraustochytrids Using Digestate from Methanization as Nitrogen Source

by Denis de la Broise, Mariana Ventura, Luc Chauchat, Maurean Guerreiro, Teo Michez, Thibaud Vinet, Nicolas Gautron, Fabienne Le Grand, Antoine Bideau, Nelly Le Goïc, Adeline Bidault, Christophe Lambert and Philippe Soudant

Mar. Drugs 2022, 20(8), 499; https://0-doi-org.brum.beds.ac.uk/10.3390/md20080499 - 02 Aug 2022

Cited by 4 | Viewed by 1847

Abstract

The production of non-fish based docosahexaenoic acid (DHA) for feed and food has become a critical need in our global context of over-fishing. The industrial-scale production of DHA–rich Thraustochytrids could be an alternative, if costs turned out to be competitive. In order to reduce production costs, this study addresses the feasibility of the non-axenic (non-sterile) cultivation of Aurantiochytrium mangrovei on industrial substrates (as nitrogen and mineral sources and glucose syrup as carbon and energy sources), and its scale-up from laboratory (250 mL) to 500 L cultures. Pilot-scale reactors were airlift cylinders. Batch and fed-batch cultures were tested. Cultures over 38 to 62 h achieved a dry cell weight productivity of 3.3 to 5.5 g.L⁻¹.day⁻¹, and a substrate to biomass yield of up to 0.3. DHA productivity ranged from 10 to 0.18 mg.L⁻¹.day⁻¹. Biomass productivity appears linearly related to oxygen transfer rate. Bacterial contamination of cultures was low enough to avoid impacts on fatty acid composition of the biomass. A specific work on microbial risks assessment (in supplementary files) showed that the biomass can be securely used as feed. However, to date, there is a law void in EU legislation regarding the recycling of nitrogen from digestate from animal waste for microalgae biomass and its usage in animal feed. Overall, the proposed process appears similar to the industrial yeast production process (non-axenic heterotrophic process, dissolved oxygen supply limiting growth, similar cell size). Such similarity could help in further industrial developments. Full article

(This article belongs to the Special Issue Marine Thraustochytrids: Biology, Chemical Ecology and Biotechnology)

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10 pages, 1234 KiB

Open AccessArticle

Development of Growth Media from Agricultural By-Products for Cultivation of PUFA-Producing Sicyoidochytrium minutum

by Heiðrún Eiríksdóttir, Magnús Örn Stefánsson and Hjörleifur Einarsson

Mar. Drugs 2022, 20(1), 8; https://0-doi-org.brum.beds.ac.uk/10.3390/md20010008 - 22 Dec 2021

Cited by 2 | Viewed by 2153

Abstract

The demand for novel sources of marine oils, which contain polyunsaturated fatty acids (PUFAs), has increased due to the realization of the importance of PUFAs, e.g., docosahexaenoic acid (DHA), in the human diet. However, the natural supply is limited. By-product peptones (BYPP) intended as a growth medium for the PUFA-producing strain Sicyoidochytrium minutum of family Thraustochytriaceae were produced after several experiments on the pancreatic digestion of bovine lungs and spleens. S. minutum was able to grow in a medium containing BYPP made from the pancreatic digestion of lung and spleen with glycerol, resulting in 1.14 ± 0.03 g cell dry weight (CDW)/L and 1.44 ± 0.24 g CDW/L, respectively, after 5 days of incubation at 25 °C, compared to 1.92 ± 0.25 g CDW/L in Basal Medium (BM) containing tryptone, peptone, and glycerol. The lipid content, obtained after growth in lung BYPP media with glycerol as a carbon source, was significantly higher (28.17% ± 1.33 of dry weight) than in the control basal medium (BM) (21.72% ± 2.45); however, DHA as a percentage of total fatty acids was lower in BYPP than in the control BM (25.24% ± 1.56 and 33.02% ± 2.37, respectively). It is concluded that low-value by-products from abattoirs can be used as ingredients for the cultivation of oligogenic Thraustochytriaceae. Full article

(This article belongs to the Special Issue Marine Thraustochytrids: Biology, Chemical Ecology and Biotechnology)

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25 pages, 2693 KiB

Open AccessArticle

Thraustochytrids of Mangrove Habitats from Andaman Islands: Species Diversity, PUFA Profiles and Biotechnological Potential

by Kaliyamoorthy Kalidasan, Nambali Valsalan Vinithkumar, Dhassiah Magesh Peter, Gopal Dharani and Laurent Dufossé

Mar. Drugs 2021, 19(10), 571; https://0-doi-org.brum.beds.ac.uk/10.3390/md19100571 - 14 Oct 2021

Cited by 10 | Viewed by 3264

Abstract

Thraustochytrids are the most promising microbial source for the commercial production of docosahexaenoic acid (DHA) for its application in the human health, aquaculture, and nutraceutical sectors. The present study isolated 127 thraustochytrid strains from mangrove habitats of the south Andaman Islands, India to study their diversity, polyunsaturated fatty acids (PUFAs), and biotechnological potential. The predominant strains were identified as belonging to two major genera (Thraustochytrium, Aurantiochytrium) based on morphological and molecular characteristics. The strain ANVKK-06 produced the maximum biomass of 5.42 g·L⁻¹, while ANVKK-03 exhibited the maximum total lipid (71.03%). Omega-3 PUFAs such as eicosapentaenoic acid (EPA) accumulated up to 11.03% in ANVKK-04, docosapentaenoic acid (DPA) up to 8.65% in ANVKK-07, and DHA up to 47.19% in ANVKK-06. ANVKK-06 showed the maximum scavenging activity (84.79 ± 2.30%) while ANVKK-03 and ANVKK-10 displayed the highest antibacterial activity against human and fish pathogens, S. aureus (18.69 ± 1.2 mm) and V. parahaemolyticus (18.31 ± 1.0 mm), respectively. All strains were non-toxic as evident by negative blood agar hemolysis, thus, the thraustochytrids are suggested to be a potential source of DHA for application in the health care of human and fish. Full article

(This article belongs to the Special Issue Marine Thraustochytrids: Biology, Chemical Ecology and Biotechnology)

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12 pages, 1538 KiB

Open AccessArticle

Elemental Composition and Cell Mass Quantification of Cultured Thraustochytrids Unveil Their Large Contribution to Marine Carbon Pool

by Biswarup Sen, Jiaqian Li, Lyu Lu, Mohan Bai, Yaodong He and Guangyi Wang

Mar. Drugs 2021, 19(9), 493; https://0-doi-org.brum.beds.ac.uk/10.3390/md19090493 - 29 Aug 2021

Cited by 5 | Viewed by 2001

Abstract

The element stoichiometry of bacteria has received considerable attention because of their significant role in marine ecosystems. However, relatively little is known about the composition of major structural elements of the unicellular heterotrophic protists—thraustochytrids, despite their widely recognized contribution to marine nutrient cycling. Here, we analyze the cell volume and elemental C, N, H, and S cell content of seven cultured thraustochytrids, isolated from different marine habitats, in the exponential and stationary growth phases. We further derive the relationships between the cell volume and elemental C and N content of the cultured thraustochytrids. The cell volumes varied significantly (p < 0.001) among the isolates, with median values of 96.9 and 212.5 μm³ in the exponential and stationary phases, respectively. Our results showed a significantly higher percentage of C (64.0 to 67.5) and H (9.9 to 13.2) but a lower percentage of N (1.86 to 2.16) and S (0.34 to 0.91) in the stationary phase, along with marked variations of C and N fractions among isolates in the exponential phase. The cell C (5.7 to 203.7 pg) and N (0.65 to 6.1 pg) content exhibited a significant (p < 0.001) linear relationship with the cell volume (27.7 to 510 μm³). On further analysis of the relationship across the two growth phases, we found the equation (cell C (pg) = 0.356 × cell volume (μm³) + 20.922) for stationary phase cells more appropriate for C estimation of natural thraustochytrids. This study provides the first experimental evidence of higher cell C density than the current estimate and relatively larger C contribution of thraustochytrids than bacteria to the marine organic pool. Full article

(This article belongs to the Special Issue Marine Thraustochytrids: Biology, Chemical Ecology and Biotechnology)

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16 pages, 2070 KiB

Open AccessArticle

Antarctic Thraustochytrids as Sources of Carotenoids and High-Value Fatty Acids

by Allison Leyton, Liset Flores, Carolina Shene, Yusuf Chisti, Giovanni Larama, Juan A. Asenjo and Roberto E. Armenta

Mar. Drugs 2021, 19(7), 386; https://0-doi-org.brum.beds.ac.uk/10.3390/md19070386 - 06 Jul 2021

Cited by 13 | Viewed by 3255

Abstract

Eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and carotenoids are needed as human dietary supplements and are essential components in commercial feeds for the production of aquacultured seafood. Microorganisms such as thraustochytrids are potential natural sources of these compounds. This research reports on the lipid and carotenoid production capacity of thraustochytrids that were isolated from coastal waters of Antarctica. Of the 22 isolates, 21 produced lipids containing EPA+DHA, and the amount of these fatty acids exceeded 20% of the total fatty acids in 12 isolates. Ten isolates were shown to produce carotenoids (27.4–63.9 μg/g dry biomass). The isolate RT2316-16, identified as Thraustochytrium sp., was the best producer of biomass (7.2 g/L in five days) rich in carotenoids (63.9 μg/g) and, therefore, became the focus of this investigation. The main carotenoids in RT2316-16 were β-carotene and canthaxanthin. The content of EPA+DHA in the total lipids (34 ± 3% w/w in dry biomass) depended on the stage of growth of RT2316-16. Lipid and carotenoid content of the biomass and its concentration could be enhanced by modifying the composition of the culture medium. The estimated genome size of RT2316-16 was 44 Mb. Of the 5656 genes predicted from the genome, 4559 were annotated. These included genes of most of the enzymes in the elongation and desaturation pathway of synthesis of ω-3 polyunsaturated fatty acids. Carotenoid precursors in RT2316-16 were synthesized through the mevalonate pathway. A β-carotene synthase gene, with a different domain organization compared to the gene in other thraustochytrids, explained the carotenoid profile of RT2316-16. Full article

(This article belongs to the Special Issue Marine Thraustochytrids: Biology, Chemical Ecology and Biotechnology)

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11 pages, 2279 KiB

Open AccessArticle

Docosahexaenoic Acid Is Naturally Concentrated at the sn-2 Position in Triacylglycerols of the Australian Thraustochytrid Aurantiochytrium sp. Strain TC 20

by Kim Jye Lee-Chang, Matthew C. Taylor, Guy Drummond, Roger J. Mulder, Maged Peter Mansour, Mina Brock and Peter D. Nichols

Mar. Drugs 2021, 19(7), 382; https://0-doi-org.brum.beds.ac.uk/10.3390/md19070382 - 01 Jul 2021

Cited by 9 | Viewed by 2442

Abstract

The Labyrinthulomycetes or Labyrinthulea are a class of protists that produce a network of filaments that enable the cells to glide along and absorb nutrients. One of the main two Labyrinthulea groups is the thraustochytrids, which are becoming an increasingly recognised and commercially used alternate source of long-chain (LC, ≥C₂₀) omega-3 containing oils. This study demonstrates, to our knowledge for the first time, the regiospecificity of the triacylglycerol (TAG) fraction derived from Australian thraustochytrid Aurantiochytrium sp. strain TC 20 obtained using ¹³C nuclear magnetic resonance spectroscopy (¹³C NMR) analysis. The DHA present in the TC 20 TAG fraction was determined to be concentrated in the sn-2 position, with TAG (16:0/22:6/16:0) identified as the main species present. The sn-2 preference is similar to that found in salmon and tuna oil, and differs to seal oil containing largely sn-1,3 LC-PUFA. A higher concentration of sn-2 DHA occurred in the thraustochytrid TC 20 oil compared to that of tuna oil. Full article

(This article belongs to the Special Issue Marine Thraustochytrids: Biology, Chemical Ecology and Biotechnology)

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Review

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19 pages, 1233 KiB

Open AccessReview

Method Development Progress in Genetic Engineering of Thraustochytrids

by E-Ming Rau and Helga Ertesvåg

Mar. Drugs 2021, 19(9), 515; https://0-doi-org.brum.beds.ac.uk/10.3390/md19090515 - 11 Sep 2021

Cited by 11 | Viewed by 3386

Abstract

Thraustochytrids are unicellular, heterotrophic marine eukaryotes. Some species are known to store surplus carbon as intracellular lipids, and these also contain the long-chain polyunsaturated fatty acid docosahexaenoic acid (DHA). Most vertebrates are unable to synthesize sufficient amounts of DHA, and this fatty acid is essential for, e.g., marine fish, domesticated animals, and humans. Thraustochytrids may also produce other commercially valuable fatty acids and isoprenoids. Due to the great potential of thraustochytrids as producers of DHA and other lipid-related molecules, a need for more knowledge on this group of organisms is needed. This necessitates the ability to do genetic manipulation of the different strains. Thus far, this has been obtained for a few strains, while it has failed for other strains. Here, we systematically review the genetic transformation methods used for different thraustochytrid strains, with the aim of aiding studies on strains not yet successfully transformed. The designs of transformation cassettes are also described and compared. Moreover, the potential problems when trying to establish transformation protocols in new thraustochytrid species/strains are discussed, along with suggestions utilized in other organisms to overcome similar challenges. The approaches discussed in this review could be a starting point when designing protocols for other non-model organisms. Full article

(This article belongs to the Special Issue Marine Thraustochytrids: Biology, Chemical Ecology and Biotechnology)

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