(430d) Metabolic Engineering of an Oleaginous Yeast for Cost-Effective Lipid Production

Lipids are an important product that can be used for the production of biofuels such as biodiesel. The latter is presently produced from vegetables and seed oils, however, its long-term cost-effective production should utilize carbohydrate feedstocks for optimal land use. To this end, we have engineered an oleaginous yeast for the high yield conversion of carbohydrates to lipids and accumulation at high titers. In light of the analysis on mammalian cellular obese phenotype, the engineering strategy followed a push-pull approach whereby the fatty acid synthesis pathway was enhanced through the overexpression of Acetyl-CoA-Carboxylase (ACC1) along with the downstream lipid storage pathway for lipid sequestration in lipid bodies. We found that both pathways are important for optimal conversion yield and productivity, which is further obtained by minimizing citrate byproduct formation and maximizing pathway throughput. Pathway throughput is maximized by reducing or eliminating regulation of fatty acid synthesis, a goal that was achieved through the modulation of various target desaturase-expressing genes. This strategy yielded sharp increases in overall growth rate and lipid synthesis in small-scale flasks and bioreactor runs. Altogether, our work demonstrates the development of an engineered oleaginous yeast, with high lipids titer and yield, which is an important step towards the development of a cost-effective process for biodiesel production from renewable resources.