Enhancing oleanolic acid production in engineered Saccharomyces cerevisiae

Oleanolic acid is a plant-derived pentacyclic triterpenoid compound with various biological activities. Recently, biosynthesis of oleanolic acid in microbes has been demonstrated as a promising and green way, but the production is too low for industrialization. To improve oleanolic acid production, this study constructed a novel pathway for biosynthesis of oleanolic acid in Saccharomyces cerevisiae by improving the pairing efficiency between cytochrome P450 monooxygenase and reductase. Furthermore, to improve the transcriptional efficiency of heterologous genes, the cellular galactose regulatory network was reconstructed by knocking out galactose metabolic genes GAL80 and GAL1. Finally, the 3-hydroxy-3-methylglutaryl-CoA reductase, squalene synthase and 2,3-oxidosqualene synthase were further overexpressed, increasing oleanolic acid production up to 186.1 +/- 12.4 mg/L in flask shake. Combined with fermentation optimization, the final oleanolic acid production was 606.9 +/- 9.1 mg/L with a yield of 16.0 +/- 0.8 mg/g DCW which was 7.6-fold higher than the reported maximum production.