Rewiring the reductive TCA pathway and glyoxylate shunt of Escherichia coli for succinate production from corn stover hydrolysate using a two-phase fermentation strategy

Abstract

Succinate was found extensive applications in the food additives, pharmaceutical, and biopolymers industries. However, the succinate biosynthesis in E. coli required IPTG, lacked NADH, and produced high yields only under anaerobic conditions, unsuitable for cell growth. To overcome these limitations, the glyoxylate shunt and reductive TCA pathway were simultaneously enhanced to produce succinate in both aerobic and anaerobic conditions and achieve a high cell growth meanwhile. On this basis, NADH availability and sugars uptake were increased. Furthermore, an oxygen-dependent promoter was used to dynamically regulate the expression level of key genes of reductive TCA pathway to avoid the usage of IPTG. The final strain E. coli Mgls7-32 could produce succinate from corn stover hydrolysate without an inducer, achieving a titer of 72.8 g/L in 5 L bioreactor (1.2 mol/mol of total sugars). Those findings will aid in the industrial production of succinate.