Optimization of Germacrene A Synthase for Efficient Production of β-Elemene in Escherichia coli

β-Elemene, a sesquiterpene from the medicinal plant Curcuma wenyujin, is commercially used in the anticancer pharmaceuticals industry. The β-elemene product from plant extraction or chemical synthesis suffers from large-scale consumption of plant or fossil resources. Herein, an efficient, sustainable, and green method with a powerful cell factory for the production of β-elemene has been developed. The efficient β-elemene production platform combined with the exogenous pathway and germacrene A synthase (GAS) was established in Escherichia coli. To address the inclusion body formation of AvGAS in E. coli, a terminal fusion strategy with peptide tags was employed to enhance the solubility of AvGAS. Subsequently, a directed evolution approach for AvGAS based on the fluorescent reporter plasmid was implemented, resulting in a significant increase in the β-elemene titer to 795.03 mg/L. Further optimization of culture conditions alongside the fed-batch fermentation increased the β-elemene titer to 2069.77 mg/L in a shake flask and to 7.74 g/L in a 1.3 L bioreactor, which is the highest reported value in E. coli to the best of our knowledge. This work shows the enormous potential production of β-elemene in E. coli and provides references to modify key rate-limiting enzymes for the sustainable production of desired natural compounds.