Metabolic Engineering of Zymomonas mobilis for Production of 2,3 Butanediol from Lignocellulosic Biomass Sugars

Zymomoonas mobilis is a well known ethanologen for both its high specific glucose uptake rate and rapid catabolism and is engineered to metabolize the major biomass sugars including D-xylose and L-arabinose.  We seek to take the advantages of the organism’s metabolic capabilities and are working to redirect the carbon flow to produce other chemicals.  In this study we investigated the production of 2,3 butanediol.  2,3 Butanediol is not only a potentially bulk chemical building block, but also can be deoxydehydrated to butenes which can be oligomerized in high yields to produce gasoline, diesel, and jet fuels. Genomic and pathway analysis showed that three homologous genes exist for acetolactate synthase in Z. mobilis.  But it lacks genes encoding for both acetolactate decarboxylase and butanediol dehydrogenase for 2,3 butanediol synthesis.  Therefore, pathway engineering is required to recruit heterologous genes into Z. mobilis to enable it producing 2,3 butanediol.  In this presentation we will present our recent work in demonstrating the production of 2,3 butanediol by engineered Z. mobilis from glucose and xylose, the two major sugars found in lignocellulosic biomass feedstocks.  Further, we showed similar fermentation performance by the engineered organism using biomass derived mixed C6/C5 sugar streams derived from the Deacetylation and Mechanic Refining (DMR) pretreatment and enzymatic hydrolysis deconstruction approach recently developed at NREL indicating that the new biomass derived mixed C6/C5 sugar streams are fermentable and much less toxic to the fermentation organism.