Continuous production of nicotinamide mononucleotide by engineered Escherichia coli: effect of dilution rate and glucose feeding.

Nicotinamide mononucleotide (NMN) is an essential intermediate with significant potential in alleviating various pathological conditions. In this study, a high cell density continuous fermentation strategy was designed and operated for 110 h to optimize NMN production using a metabolically engineered Escherichia coli strain. By controlling the dilution rate and glucose feeding, the system achieved a balance between substrate supply, cellular uptake, and metabolic conversion over a 60-h period. Under the optimal conditions (D = 0.2 h⁻¹ and glucose feed concentration of 280 g/L), NMN production reached 17.8–18.2 g/L, with conversion yields of 2.64 g NMN from g nicotinamide and 0.066 g NMN from g glucose. In contrast, the highest productivity of 4.14–4.26 g/L/h was observed at D = 0.3 h⁻¹, despite a decrease in NMN concentration to 13.8–14.2 g/L. The process maintained high biomass density and stable product output over extended operation, demonstrating substantial potential for scale-up in NMN manufacturing. This approach underscores the importance of optimizing operational parameters as a sustainable and practical route for industrial biotechnology applications.