High-Level Production of Nicotinamide Mononucleotide by Engineered <i>Escherichia Coli</i>

Nicotinamide mononucleotide (NMN), a key precursor of NAD⁺, is a promising nutraceutical due to its excellent efficacy in alleviating aging and disease. The bioproduction of NMN faces challenges related to incomplete metabolic engineering and insufficient metabolic flux. Here, we constructed an NMN synthesis pathway in <i>Escherichia coli</i> BW25113 by deleting the competitive pathway genes and introducing three heterologous genes encoding the key enzymes nicotinamide phosphoribosyltransferase (NAMPT), phosphoribosyl pyrophosphate synthetase and an NMN transporter. Next, the identification of a highly active NAMPT and optimization of gene expression markedly increased the conversion of NAM to NMN, with a titer of 3503.85 mg/L in shake flasks. Furthermore, by facilitating the coutilization of glucose and xylose, more metabolic flux was diverted toward PRPP biosynthesis, resulting in an NMN titer of 15.66 g/L through whole-cell catalysis and 46.66 g/L in a 2-L bioreactor. This represents the highest NMN yield reported to date, exhibiting great potential for initiating sustainable industrial production of NMN.