Enhanced β-Amyrin Synthesis in Saccharomyces cerevisiae by Coupling An Optimal Acetyl-CoA Supply Pathway.

β-Amyrin is a plant-derived triterpenoid skeleton with wide applications in food and medical industry. β-Amyrin biosynthesis in Saccharomyces cerevisiae is derived from the mevalonate pathway with cytosolic acetyl-CoA as a precursor. In this work, endogenous and several heterologous acetyl-CoA synthesis pathways were coupled to β-amyrin production and a combinational acetyl-CoA supply route was demonstrated to be optimal due to more balanced redox cofactors, much lower energy consumption, and glucose utilization as well as significantly enhanced β-amyrin production (a 200% increase compared to the original β-amyrin-producing strain). Further disruption of an acetyl-CoA competing pathway led to a 330% increase in β-amyrin production as compared to the original strain. Finally, the engineered strain harboring the optimal pathway configuration achieved a final β-amyrin production of 279.0 ± 13.0 mg/L in glucose fed-batch fermentation, which is the highest as ever reported. This work provides an efficient platform for triterpenoid biosynthesis in Saccharomyces cerevisiae.