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

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.

Ultraviolet and 5'fluorodeoxyuridine induced random mutagenesis in Chlorella vulgaris and its impact on fatty acid profile: a new insight on lipid-metabolizing genes and structural characterization of related proteins.

The present study was aimed at randomly mutating the microalga, Chlorella vulgaris, in order to alter its cellular behaviour towards increased lipid production for efficient biodiesel production from algal biomass. Individual mutants from ultraviolet light (UV-1 (30 s exposure), UV-2 (60 s exposure) and UV-3 (90 s exposure)) and 5'fluorodeoxyuridine (5'FDU-1 (0.25 mM) and 5'FDU-2 (0.50 mM)) exposed cells were identified to explore an alternative method for lipid enhancement. A marginally significant decrease in biomass in the UV mutants; marked increase in the lipid content in UV-2 and 5'FDU-1 mutants; significant increase in saturated fatty acids level, especially in UV-2 mutant; insignificant increase in lipid production when these mutants were subjected to an additional stress of nitrogen starvation and predominantly enhanced level of unsaturated fatty acids in all the strains except UV-2 were noted. Chloroplast ultrastructural alterations and defective biosynthesis of chloroplast specific lipid constituents were observed in the mutants. Modelling of three-dimensional structures of acetyl coA carboxylase (ACCase), omega-6, plastid delta-12 and microsomal delta-12 fatty acid desaturases for the first time and ligand-interaction studies greatly substantiated our findings. A replacement of leucine by a serine residue in the acetyl coA carboxylase gene of UV-2 mutant suggests the reason behind lipid enhancement in UV-2 mutant. Higher activity of ACCase in UV-2 and 5'FDU-1 strongly proves the functional consequences of gene mutation to lipid production. In conclusion, algal mutants exhibited significant impact on biodiesel production through structural alterations in the lipid-metabolizing genes, thereby enhancing lipid production and saturated fatty acid levels.