Metabolic Engineering of a 1,2-Propanediol Pathway in Escherichia coli

Abstract

ABSTRACT 1,2-Propanediol (1,2-PD) is a major commodity chemical that is currently derived from propylene, a nonrenewable resource. A goal of our research is to develop fermentation routes to 1,2-PD from renewable resources. Here we report the production of enantiomerically pure R -1,2-PD from glucose in Escherichia coli expressing NADH-linked glycerol dehydrogenase genes ( E. coli gldA or Klebsiella pneumoniae dhaD ). We also show that E. coli overexpressing the E. coli methylglyoxal synthase gene ( mgs ) produced 1,2-PD. The expression of either glycerol dehydrogenase or methylglyoxal synthase resulted in the anaerobic production of approximately 0.25 g of 1,2-PD per liter. R -1,2-PD production was further improved to 0.7 g of 1,2-PD per liter when methylglyoxal synthase and glycerol dehydrogenase ( gldA ) were coexpressed. In vitro studies indicated that the route to R -1,2-PD involved the reduction of methylglyoxal to R -lactaldehyde by the recombinant glycerol dehydrogenase and the reduction of R -lactaldehyde to R -1,2-PD by a native E. coli activity. We expect that R -1,2-PD production can be significantly improved through further metabolic and bioprocess engineering.