Flux optimization for improved caproic acid production in Escherichia coli

Abstract

The purpose of this study is to demonstrate that rebalancing of metabolic fluxes at acetyl-CoA branch node can substantially improve the titer and productivity of hexanoic acid in recombinant Escherichia coli strains. First, a hexanoic acid-producing E. coli strain was constructed by expressing genes encoding β-ketothiolase from Cupriavidus necator and acetyl-CoA transferase from Megasphaera sp. MH in a butyric acid producer strain. Next, metabolic flux was optimized at the acetyl-CoA branch node by fine-tuning the expression level of the gene for acetyl-CoA acetyltransferase. Four synthetic 5′-UTR regions were designed for atoB using UTR Designer to modulate the expression level of the gene. Notably, the productivity of the optimized strain (14.7 mg/L/h) was the highest among recombinant E. coli strains in literature when using a similar inoculum size for fermentation. These results show that fine-tuning the expression level of atoB is critical for production of hexanoic acid.

Keywords: Flux optimization, hexanoic acid, metabolic engineering