(474d) Engineering of Oleaginous Escherichia Coli for Hydrocarbon Production

Fatty acid derived hydrocarbons, such as long-chain alkane, alkene and biodiesel, are promising biofuels. Previous works have demonstrated the feasibility of their production in E. coli. However, the yield and efficiency remains low, which prevents economical scale-up to industrial processes. The goal of this project is to design and construct efficient E. coli strains to produce and accumulate fatty acids in the form of wax ester and triacylglycerol, similar to oleaginous species. This approach can potentially enable very high level of hydrocarbon production as it overcomes the toxicity issue associated with long-chain hydrocarbons by forming carbon-rich self-organized lipid bodies.

Our genetic modifications of E. coli focus on both the fatty acid biosynthesis/conversion pathways and the central carbon metabolic network that provides key precursors. We employed metabolic and regulatory network modeling to design optimal strains for fatty acid production and specific reactions involved in the central carbon metabolism have been suggested for knockout or reactivation. We also modified the fatty acid pathway substantially and our designed manipulations include knockout of acyl-CoA dehydrogenase (fadE) to block β-oxidation, cytosolic expression of an E. coli native tioestesrase (TE), and overexpression of four subuits of acetyl-CoA carboxylase (ACC). In order to convert the over-produced fatty acids to wax ester and triacylglycerol, heterologous expression of Arabidopsis fatty acyl-CoA reductase and bacterium wax ester synthase/acyl-CoA-diacylglycerol acyltransferase (WS/DGAT) will also be incorporated. The resulted E. coli strains are expected to produce and accumulate abundant fatty acids, which can be further converted to hydrocarbon either biologically or chemically.