Recombinant production of omega-3 fatty acids in Escherichia coli using a gene cluster isolated from Shewanella baltica MAC1

Abstract

To isolate eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) genes from Shewanella baltica MAC1 and to examine recombinant production of EPA and DHA in E. coli to investigate cost-effective, sustainable and convenient alternative sources for fish oils. A fosmid library was prepared from the genomic DNA of S. baltica MAC1 and was screened for EPA and DHA genes by colony hybridization using a partial fragment of the S. baltica MAC1 pfaA and pfaD genes as probes. Analysis of total fatty acids isolated from transgenic E. coli positive for pfaA and pfaD genes by gas chromatography and gas chromatography-mass spectrometry indicated recombinant production of both EPA and DHA. Analysis of the complete nucleotide sequence for the isolated gene cluster showed 16 putative open reading frames (ORFs). Among those, four ORFs showed homology with pfaA, pfaB, pfaC and pfaD genes of the EPA and/or DHA biosynthesis gene clusters; however, the protein domains of these genes were different from other EPA/DHA biosynthesis genes. The EPA and DHA gene cluster was cloned successfully. The transgenic E. coli strain carrying the omega-3 gene cluster was able to produce both EPA and DHA. The isolated gene cluster contained all the genes required for the recombinant production of both EPA and DHA in E. coli. These findings have implications for any future use of the EPA and DHA gene cluster in other micro-organisms, notably those being used for fermentation. Recombinant production of both EPA and DHA by E. coli or any other micro-organism has great potential to add economic value to a variety of industrial and agricultural products.