Combinatorial Engineering of Mevalonate Pathway and Diterpenoid Synthases in Escherichia coli for cis-Abienol Production.

Identification of diterpene synthase-encoding genes together with synthetic biology technology offers an opportunity for the biosynthesis of cis-abienol. The methylerythritol phosphate (MEP) and the mevalonate (MVA) pathways were both engineered for cis-abienol production in Escherichia coli, which improved the cis-abienol yield by approximately 7-fold and 31-fold, respectively, compared to the yield obtained by overexpression of the MEP pathway alone or the original MEP pathway. Furthermore, systematic optimization of cis-abienol biosynthesis was performed, such as diterpene synthase screening and two-phase cultivation. The combination of bifunctional class I/II cis-abienol synthase from Abies balsamea ( AbCAS) and class II abienol synthase from Salvia sclarea ( SsTPS2) was found to be the most effective. By using isopropyl myristate as a solvent in two-phase cultivation, cis-abienol production reached 634.7 mg/L in a fed-batch bioreactor. This work shows the possibility of E. coli utilizing glucose as a carbon source for cis-abienol biosynthesis through a modified pathway.