The diversity and biotechnological application of marine microbes producing omega-3 fatty acids

Abstract

Omega-3 polyunsaturated fatty acids (PUFAs), such as eicosapentaenoic acid (EPA, 20:5ω3) and docosahexaenoic acid (DHA, 22:6ω3) play a role in the modulation and prevention of human diseases, in particular cardiovascular diseases. The omega-3 family is found mainly in fish, of which wild stocks are becoming limited. Therefore production of omega-3 PUFAs by marine microbes may provide an alternative source of such componds. The diversity of marine microbes was studied using 16S/18S rRNA gene sequencing of different marine biota with 1500 bacterial strains and 50 microalgae were isolated. The diversity of culturalbe microorganisms inhabiting Mid-Atlantic Ridge (MAR) non-vent sediments was examined for the first time in this area with findings of high diversily of Gram-positive strains, good production of squalene by an unusual strain Bacillus sp. MAR089 and the highest yield of EPA ever recovered from strain Shewanella sp. MAR441. North Sea sponge associated Vibrio sp. strain NSP560 produced considerable levels of EPA, whereas no PUFAs producers were found from tropic Caribbean marine sponge associated bacteria. Photobacterium sp. strain MA665, isolated from the coast of North Sea, was described for the first time of this genus and could be cultured easily under atmospheric conditions with appreciable levels of EPA -1 with up to 25 % of total fatty acids (TFA) (or 10.6 mg g in dried cell). Strain MAR441 was identified as a new species, designated as Shewanella dovemarina sp. T nov. (Type strain MAR441 ). The level of EPA production of strain MAR441 has been optimized by varying fermentation conditions, and 15-25 % EPA of TFA (or 17-30 mg -1 g in dried cell) could be achieved with 40 % improvement. In order to understand the PUFAs biosynthesis pathways and better predict the maximum EPA production, EPA gene clusters (pfaA, pfaB, pfaC, pfaD and pfaE) were cloned and sequenced from the following three species Shewanella, Vibrio and Photobacterium. Great potential was found in marine algae Phaeodactylum tricornutum strain M7 with lipid content of 10 % in dry wt biomass and 22-30 % EPA of TFA when it was cultured outdoors under local weather conditions in UK. Under anaerobic conditions, strain MAR441 contained less -2 amount of EPA and produced electricity of ~100 mW m . Enhanced electricity production using artificial consortia of estuarine bacteria grown as biofilms was -2 observed with power generation of ~200 mW m . In conclusion, bacteria taxonomic resolution based on complete cell fatty acid composition is possible and marine microbes with considerable production of EPA could be potential candidates for industrial production of PUFAs.