Constructing a Synthetic Metabolic Pathway Protects Escherichia coli Against the Acetic Acid Inhibition and Fulfills Enantiomerically Pure (R, R)-2,3-Butanediol Production

Enantiomerically pure (R, R)-2,3-butanediol has unique applications due to its special chiral group and spatial configuration. Currently, its chemical production route has many limitations. In addition, no native microorganisms can accumulate (R, R)-2,3-butanediol with an enantio-purity over 99%. Herein, we constructed a synthetic metabolic pathway for enantiomerically pure (R, R)-2,3-butanediol biosynthesis in Escherichia coli. The fermentation results suggested that introduction of the sythetic metabolic pathway redistributed the carbon fluxes to the neutral (R, R)-2,3-butanediol, and thus protected the strain against the acetic acid inhibition. Additionally, it showed that the traditionally used isopropyl beta-D-thiogalactoside (IPTG) induction displayed negative effect on (R, R)-2,3-butanediol biosynthesis in the recombinant E. coli, which was probably due to the protein burden. With no IPTG addition, the (R, R)-2,3-butanediol concentration reached 115 g/L by fed-batch culturing of the recombinant E. coli, with an enantio-purity over 99%, which is a new record of enantiomerically pure (R, R)-2,3-butanediol production.