Heterologous Orthogonal Fatty Acid Biosynthesis System in Escherichia coli for Oleochemical Production
Producing biofuels and bioproducts from biomass requires the construction of efficient biosynthetic pathways. The introduction of heterologous enzymes into the well-established model microbe, Escherichia coli, can have the benefits of expanding the metabolite produced while avoiding feedback inhibition. Researchers at the Department of Energy’s Joint BioEnergy Institute expressed several heterologous type I fatty acid synthases (FAS) in E. coli that functioned in parallel with the native FAS. The most active heterologous FAS expressed in E. coli was Corynebacterium glutamicum FAS1A and resulted in the production of oleochemicals including fatty alcohols and methyl ketones. Chain length distribution of fatty alcohols produced shifted with coexpression of FAS1A with the acyl carrier protein/coenzyme A (CoA)-reductase from Marinobacter aquaeolei (Maqu2220). Coexpression of FAS1A with the Micrococcus luteus acyl-CoA-oxidase (FadM, FadB) resulted in the production of methyl ketones, although at a lower level than cells using the native FAS. This work is believed to be the first example of in vivo function of a heterologous FAS in E. coli. Functional expression of these large enzyme complexes in E. coli will enable their study without the need to culture the native organisms as well as enable the study of FAS from uncultured organisms. In addition, using FAS1 enzymes for oleochemical production has several potential advantages, and further optimization of this system could lead to strains with more efficient conversion of biomass to desired biofuels and bioproducts.
Haushalter, R. W., D. Groff, S. Deutsch , L. The, T. A. Chavkin, S. F. Brunner, L. Katz, and J. D. Keasling. 2015. “Development of an Orthogonal Fatty Acid Biosynthesis System in Escherichia coli for Oleochemical Production,” Metabolic Engineering 30, 1-6. DOI: 10.1016/j.ymben.2015.04.003.