Efficient Succinate Production from Corn Stover Hydrolysate in Escherichia coli by Systemically Regulating Pathway Modules and Using Oxygen-Responsive Metabolic Switch

Succinate has long been considered as one of the top building block chemicals. However, the development of nonfood succinate production still remains challenging. In this study, by activating the glyoxylate shunt pathway, rewiring carbon flux, regulating reductive tricarboxylic acid (rTCA) expression, enhancing substrate uptake, and optimizing NADH supply and product efflux, a plasmid-free and noninducible engineered Escherichia coli for efficient succinate production from corn stover hydrolysate was constructed. Among them, this was the first to report that succinate production and xylose metabolism could be effectively enhanced by applying the oxygen-responsive metabolic switch (OMS) to regulate genes expression of rTCA entire pathway. The engineered E. coli BW-27 produced 16.13 g/L succinate with a yield of 1.05 g/g (total sugars) in serum bottle fermentation. Further, the biomass at the optimal aerobic–anaerobic fermentation shift time was increased by regulation of Pta expression. The final engineered strain, E. coli BW-30, was able to produce 92.6 g/L succinate with a yield of 0.89 g/g (total sugars) by metabolizing corn stover hydrolysate, which, to the best of our knowledge, is the highest titer of succinate produced by E. coli using cellulose hydrolysate reported to date. These strategies will contribute to the development of efficient cell factories for the production of succinate and related products.