CO2 fixation for succinic acid production by engineered Escherichia coli co-expressing pyruvate carboxylase and nicotinic acid phosphoribosyltransferase

Abstract In wild-type Escherichia coli , 1 mol of CO 2 was fixated in 1 mol of succinic acid generation anaerobically. The key reaction in this sequence, catalyzed by phosphoenolpyruvate carboxylase (PPC), is carboxylation of phosphoenolpyruvate to oxaloacetate. Although inactivation of pyruvate formate-lyase and lactate dehydrogenase is found to enhance the PPC pathway for succinic acid production, it results in excessive pyruvic acid accumulation and limits regeneration of NAD + from NADH formed in glycolysis. In other organisms, oxaloacetate is synthesized by carboxylation of pyruvic acid by pyruvate carboxylase (PYC) during glucose metabolism, and in E. coli , nicotinic acid phosphoribosyltransferase (NAPRTase) is a rate-limiting enzyme of the NAD(H) synthesis system. To achieve the NADH/NAD + ratio decrease as well as carbon flux redistribution, co-expression of NAPRTase and PYC in a pflB , ldhA , and ppc deletion strain resulted in a significant increase in cell mass and succinic acid production under anaerobic conditions. After 72 h, 14.5 g L −1 of glucose was consumed to generate 12.08 g L −1 of succinic acid. Furthermore, under optimized condition of CO 2 supply, the succinic acid productivity and the CO 2 fixation rate reached 223.88 mg L −1  h −1 and 83.48 mg L −1  h −1 , respectively.