Systematic Metabolic\nEngineering for Enhanced Cytidine\n5′-Monophosphate Production in <i>Escherichia coli</i>

Cytidine 5′-monophosphate (5′-CMP) is a\nkey intermediate\nin various nucleotide derivatives and is widely used in the food and\npharmaceutical industries. In this study, the titer of 5′-CMP\nin engineered Escherichia coli CM006,\nwhich blocks the degradation pathway of 5′-CMP, increased 134.7-fold\ncompared to E. coli MG1655. Integrated\nexpression of the 5′-CMP diphosphate hydrolase gene <i>nudG</i> significantly enhanced the 5′-CMP titer, reduced\norotic acid accumulation, and alleviated feedback inhibition in the\n5′-CMP synthesis pathway. By blocking cytidine degradation\nand increasing carbon flux from cytidine to 5′-CMP, the 5′-CMP\ntiter in E. coli CM011 was increased\nto 338.2 mg/L. Furthermore, by enhancing the supply of the precursor\n5-phospho-α-D-ribose 1-diphosphate (PRPP), the 5′-CMP\ntiter in E. coli CM012 reached 417.9\nmg/L, the highest value reported to date. The results and methods\npresented in this study are of great significance for the sustainable\nindustrial production of 5′-CMP.