De Novo Biosynthesis of Free Vaccenic Acid with a Low Content of Oleic Acid in Saccharomyces cerevisiae

Omega-7 (omega-7) fatty acids have potential application in the fields of nutraceutical, agricultural, and food industry. The natural omega-7 fatty acids are currently from plants or vegetable oils, which are unsustainable and limited by the availability of plant sources. Here, we developed an innovative biosynthetic route to produce vaccenic acid (C18:1 omega-7) while minimizing oleic acid (C18:1 omega-9) content in Saccharomyces cerevisiae. We have engineered S. cerevisiaeto produce C18:1 omega-7 by expressing a fatty acid elongase from Rattus norvegicus. To reduce the content of C18:1 omega-9, the endogenous desaturase Ole1 was replaced by the desaturase, which has specific activity on palmitoyl-coenzyme A (C16:0-CoA). Finally, the production of free C18:1 omega-7 was improved by optimizing the source of cytochrome b5 and overexpressing endoplasmic reticulum chaperones. After combining these strategies, the yield of C18:1 omega-7 was increased from 0 to 9.3 mg/g DCW and C18:1 omega-9 was decreased from 25.2 mg/g DCW to 1.6 mg/g DCW. This work shows a de novo synthetic pathway to produce the highest amount of free C18:1 omega-7 with a low content of C18:1 omega-9 in S. cerevisiae.