Pathway Engineering to Improve Hydrocarbon Production in Zymomonas

Zymomonas mobilis has been a favorite organism for genetic engineering for efficient conversion of lignocellulosic biomass to ethanol because of its natural tolerance to ethanol and high sugar concentrations, fast sugar utilization rate, low biomass yield, high product yield and its ability to grow and ferment under anaerobic conditions. By applying classical recombinant DNA technologies and advanced genetic tools, we have not only augmented Z. mobilis for efficient ethanol production from pretreated corn stover hydrolysates, but also further introduced and expressed heterologous genes into Z. mobilis for hydrocarbon production, taking advantage of a native terpenoid biosynthetic pathway and the key intermediates, dimethylallyl diphosphate and farnesyl diphosphate. The initial yield of hydrocarbon has been lower than desired for an economical process. We have begun to focus on strategies to improve the production by understanding and modulating the terpenoid and other metabolic pathways in Zymomonas. Several key genes are being studied for their effect on enhancing the carbon flux toward the hydrocarbon product. Here we will report on the progress of the pathway engineering in a hydrocarbon-producing Z. mobilis strain and the impact of the engineering on the production of hydrocarbon (s).