Engineering Lipid Droplet Assembly Mechanisms for Improved Triacylglycerols Accumulation in S. cerevisiae
Production of triacylglycerols (TAGs) through microbial fermentation is an emerging alternative to plant and animal-derived sources. The yeast Saccharomyces cerevisiae is a preferred organism for industrial use but has natively a very poor capacity of TAG production and storage. Here, we engineered S. cerevisiae for accumulation of high TAG levels through the use of structural and physiological factors that influence assembly and biogenesis of lipid droplets. First, human and fungal perilipin genes were expressed, increasing TAG content by up to 36% when expressing the human perilipin gene PLIN3. Secondly, expression of the FIT2 homologue YFT2 resulted in a 26% increase in TAG content. Lastly, the genes ERD1 and PMR1 were deleted in order to induce an ER stress response and stimulate lipid droplet formation, increasing TAG content by 72% for {Delta}erd1, with an additive effect for both YFT2 and PLIN3 expression. These new approaches were implemented in previously engineered strains that carry high flux of fatty acid biosynthesis and conversion of acyl-CoA into TAG, resulting in improvements of up to 138% over those high-producing strains without any substantial growth effects or abnormal cell morphology. We find that these approaches are not only a major advancement in engineering S. cerevisiae for TAG production, but also highlight the importance of lipid droplet dynamics for high lipid accumulation in yeast.