Modular reconstruction and multilevel regulation of Saccharomyces cerevisiae to drive the efficient synthesis of asiatic acid

Asiatic acid, a pentacyclic triterpenoid compound, is highly valued in the fields of functional foods, pharmaceuticals, and cosmetics. However, its microbial synthesis has been constrained by an insufficient supply of key precursors. Additional challenges include cytotoxicity caused by intracellular terpenoid accumulation and imbalanced carbon metabolism. In this study, a high-yielding Saccharomyces cerevisiae platform strain was designed through modular reconstruction and multilevel metabolic engineering to enable efficient asiatic acid production. The supply of the critical precursor, α-amyrin, was enhanced by metabolic engineering, while cytotoxicity was alleviated via Raman spectroscopy-guided lipid droplet engineering. The catalytic efficiency of key P450 enzymes involved in ursolic acid synthesis was optimized, and mitochondrial engineering combined with cofactor balancing was employed to rectify metabolic flux imbalance and energy supply. Using this engineered platform strain, key enzymatic genes were introduced to construct an asiatic acid-producing strain. A fed-batch fermentation process in a 5 L bioreactor achieved an asiatic acid titer of 170.4 mg/L. A valuable reference for the efficient biosynthesis of asiatic acid and other triterpenoids is offered by the engineered platform established in this study.