Whole-cell synthesis of nicotinamide mononucleotide by recombinant Saccharomyces cerevisiae from glucose and nicotinamide

β-Nicotinamide mononucleotide is recognized as a significant bioactive nucleotide, which is can be used in the fields of health industries. Many studies on the synthesis of NMN have involved Escherichia coli and the current methods are limited by safety problems as well as the expense of the substrate. Herein, GRAS-grade Saccharomyces cerevisiae was chosen as chassis cells to synthesize NMN using the substrates glucose and nicotinamide. First, the gene for the key enzyme nicotinamide phosphoribosyltransferase (Nampt) was screened from different sources, and site-directed mutation was performed to improve the synthesis of NMN. The concentration of intracellular NMN in yeast expressing the D83N-Nampt mutant derived from Chitinophaga pinensis reached 413.4 mg/L, which was 3.7 times higher than that of yeast expressing wild enzymes. The synthesis of NMN was further enhanced by overexpressing Nampt combined with weakening of the further metabolism of NMN. Subsequently, the supply of precursor phosphate ribose pyrophosphate (PRPP) was increased by overexpressing the PRPP synthase mutant, which led to the concentration of intracellular NMN increased to 775.9 mg/L from 537.8 mg/L. Finally, the concentration of intracellular NMN reached 1.2 g/L at 6 h after whole-cell catalytic optimization, which is the highest titer achieved by S. cerevisiae from inexpensive substrate glucose and nicotinamide. This study provides the synthesis of NMN by S. cerevisiae with a new and promising method.