Dana M. Walters Pollak

Production of omega-3 eicosapentaenoic acid by metabolic engineering of Yarrowia lipolytica

The availability of the omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) is currently limited because they are produced mainly by marine fisheries that cannot keep pace with the demands of the growing market for these products. A sustainable non-animal source of EPA and DHA is needed. Metabolic engineering of the oleaginous yeast Yarrowia lipolytica resulted in a strain that produced EPA at 15% of dry cell weight. The engineered yeast lipid comprises EPA at 56.6% and saturated fatty acids at less than 5% by weight, which are the highest and the lowest percentages, respectively, among known EPA sources. Inactivation of the peroxisome biogenesis gene PEX10 was crucial in obtaining high EPA yields and may increase the yields of other commercially desirable lipid-related products. This technology platform enables the production of lipids with tailored fatty acid compositions and provides a sustainable source of EPA.

Metabolic engineering of an oleaginous yeast for the production of omega-3 fatty acids.

Publisher Summary Numerous clinical studies have demonstrated that the omega-3 fatty acids in fish oil significantly reduce the risk of cardiovascular disease in adults. This chapter discusses the approach to introduce the genes encoding an omega-3 fatty acid biosynthesis pathway into an oleaginous yeast that synthesizes and stores triglycerides as an energy reserve when starved for nitrogen in the presence of an excess carbon source, such as glucose. It explains the development of a clean and sustainable source of omega-3 fatty acids by fermentation, which uses a metabolically engineered strain of the oleaginous yeast Y. lipolytica. While certain strains of Y. lipolytica can accumulate oil up to 40% of the dry cell weight, the only Polyunsaturated Fatty Acid (PUFA) normally synthesized by the organism is Linoleic Acid (LA). Coordinate expression of desaturase genes and elongase genes comprising a “delta6 pathway” was sufficient to demonstrate the synthesis of Eicosapentaenoic Acid (EPA). However, only an integrated strategy, based on the use of strong promoters, an increase in gene copy numbers, the push and pull of carbon into the engineered pathway, and the use of oleaginous condition, resulted in the generation of a high EPA production strain.