Construction of a redox-coupled pathway co-metabolizing glucose and acetate for high-yield production of butyl butyrate in Escherichia coli.

[Display omitted] • A redox balance strategy was developed to product butyl butyrate (BB) anaerobically. • Acetate and glucose were metabolized stoichiometrically by the engineered E. coli. • The engineered E. coli was able to maintain the intracellular redox homeostasis. • The highest titer and carbon yield of BB ever reported in E. coli were obtained. The carbon and energy efficiency of a biomanufacturing process is of crucial importance in determining its economic viability. Formate dehydrogenase has been demonstrated to be beneficial in regenerating NADH from formate produced during sugar metabolism, thereby creating energy-efficient systems. Nevertheless, introducing enzyme(s) for butyryl butyrate (BB) biosynthesis based on this system, only 1.64 g/L BB with 14.3 % carbon yield was obtained due to an imbalance in NADH-NAD+ turnover. To address the issue of NADH accumulation, a joint redox-balanced pathway for BB biosynthesis was developed in this study by coupling acetate and glucose metabolism. Following overexpression of acetyl-CoA synthetase in the BB-producing strain, acetate and glucose were co-utilized stoichiometrically and intracellular redox homeostasis was achieved. The engineered strain produced 29.02 g/L BB with carbon yield of 43.3 %, representing the highest yield ever reported for fermentative production of BB. It indicated the potential for developing a carbon- and energy-effective route for biomanufacturing. [ABSTRACT FROM AUTHOR]