Identification and Functional Characterization of Two Novel Fatty Acid Genes from Marine Microalgae for Eicosapentaenoic Acid Production

Marine microalgae such as Isochrysis sp. and Pavlova sp. are the predominant source of polyunsaturated fatty acids (PUFAs) such as eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3). EPA biosynthesis pathway is predominant in lower eukaryotes, and its biosynthetic gene expressions are not well established. Till date, the C18 elongation enzymes for EPA biosynthesis have not been identified from lower eukaryote. In the present study, we describe the identification of two microalgal genes Delta 6-elongase and Delta 5-desaturase involved for EPA biosynthesis. By PCR-based technique, a novel elongase gene (Delta 6Elo-Iso) was isolated from Isochrysis sp., and 654 bp of full-length sequence was identified, which catalysed the conversion of SDA into ETr in E. coli. The identified gene displayed unique substrate specificity for both n-3 and n-6 C18-substrates for Delta 6-elongation, with no activity towards Delta 9-elongase. In addition, a novel Delta 5-desaturase gene (Delta 5Des-Pav) was isolated from Pavlova sp. and found an ORF of 1149 bp in length, which was capable of converting ETr into EPA in omega-3 pathway. For the first time, the heterologous expressions of two novel microalgal genes were successfully expressed in Escherichia coli. EPA production from E. coli is being considered as an alternative and economic source for industrial and pharmaceutical sectors.