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.
Omega-3 long-chain polyunsaturated fatty acids (LCPUFAs), which include EPA (C20: 5n - 3) and DHA (C22: 6n - 3), are natural products that are thought to be essential for human health. In addition to their use as health supplements, EPA and DHA are also used in pharmaceutical, aquaculture, terrestrial animal feed, pet food and personal care. The demand for EPA and DHA is growing, but most commercially available EPA and DHA are produced using wild-caught ocean fish. We report the metabolic engineering of Y. lipolytica to provide a commercially viable, sustainable, land-based source of EPA and other valuable LCPUFAs.
EPA and DHA have crucial roles in the structure and function of cellular membranes and are precursors to several important eicosanoids, including prostacyclins, leukotrienes and prostaglandins (1), (2). Human clinical studies have documented the health benefits of omega-3 LCPUFAs (3). Of particular interest is the Japan EPA Lipid Intervention Study (JELIS), which showed that ingestion of EPA reduced major coronary events by 19% in patients with a history of coronary artery disease (4), and the AMR101 study, which showed that ingestion of pure EPA reduced triglyceride (TAG) concentrations in adult patients with severe hypertriglyceridemia (5). Highly purified EPA, such as Epadel and Vascepa, or mixtures of EPA and DHA, such as Lovaza, are prescribed to reduce TAG concentrations. Clinical studies using EPA lipids derived from the engineered Y. lipolytica strain that we describe in this report confirmed that the ingestion of EPA reduced TAG concentrations and also showed that EPA and DHA are functionally distinct and have different physiological and pharmacological roles in human health (6), (7).
EPA and DHA are synthesized de novo in marine microorganisms and phytoplankton and accumulate in other species through the food chain. EPA and DHA are synthesized by either an anaerobic polyketide synthase pathway (8) or an aerobic desaturase and elongase pathway (9-11). The aerobic pathway can be further classified into a [DELTA]-6 desaturase pathway (the [DELTA]-6 pathway, found in algae, mosses, fungi and others) or a [DELTA]-9 elongase and [DELTA]-8 desaturase pathway (the [DELTA]-9 pathway, found in euglenoids). Land-based production of EPA and DHA using a variety of...