Metabolic engineering of Saccharomyces cerevisiae for biosynthesis of the anticarcinogen precursor germacrene A

β-elemene, a clinically approved antineoplastic agent, is isolated from Curcuma wenyujin at low abundance. Germacrene A is its direct precursor. To overcome the supply bottleneck, we systematically rewired the mevalonate pathway of Saccharomyces cerevisiae to expand the universal C15 precursor pool. Among 19 screened germacrene A synthases, DeGAS from Daldinia eschscholtzii yielded 399.8 mg/L. Fusion of DeGAS to farnesyl pyrophosphate synthase via the rigid (EAAAK)₂ linker increased the titer to 492 mg/L, and triplication of the ERG20-DeGAS cassette further raised it to 985.5 mg/L. In a 5-L fed-batch bioreactor, germacrene A reached 19.82 g/L, a 20-fold gain over shake-flask cultures, and comparable to the highest titers previously reported in S. cerevisiae. This work provides a scalable microbial route to β-elemene and demonstrates a general strategy for sesquiterpene overproduction.