A genetically engineered type of yeast provides an abundant and sustainable supply of eicosapentanoic acid (EPA), one of the most vital components of fish oil, reports a study published online this week in Nature Biotechnology. This oil is available as a dietary supplement and as an enrichment to fish feed, enabling the farmed salmon on sale in stores in the United States to be sustainably produced for the first time.
Fish oils have long been recognized for their beneficial effects on human health, but as marine fish stocks are already under great pressure, sustainable sources to satisfy the ever-growing demand for these oils are needed. The health benefits of fish oil are largely attributed to the fact that they are rich in certain fatty acids, especially omega-3 long chain polyunsaturated fatty acids. These molecules are not made by fish but by marine microorganisms that fish eat. Despite intensive efforts, growing these microorganisms on an industrial scale has proven difficult.
Quinn Zhu and colleagues genetically engineered a yeast, Yarrowia lipolytica, which can be easily grown in large quantities and naturally produces substantial amounts of oil, to make EPA. To generate such a highly efficient production pathway, they needed to introduce 21 foreign genes into the yeast and to knock out one natural yeast gene. The authors report that up to 30% of the cell dry weight and more than half of the lipid of the new yeast strain consists of EPA. Yarrowia lipolytica is already used commercially to produce human nutritional supplements and as a feedstock to provide EPA to farmed salmon.