Nicotinamide mononucleotide production by non-recombinant <i>Limosilactobacillus reuteri</i> and nicotinamide adenine dinucleotide synthesizing lactic acid bacteria

β-nicotinamide mononucleotide (NMN) is a precursor of nicotinamide adenine dinucleotide (NAD⁺) and has the potential to suppress aging. Despite its increasing use in recent years, the production cost of NMN remains high. Certain strains of lactic acid bacteria (LAB), which are widely used in the fermentation of foods and are marketed as probiotics due to their safety and functional benefits, offer a promising alternative for the cost-effective production of functional compounds. However, the production of NMN by non-recombinant LAB has rarely been investigated except for some specific species. Our study has discovered that <i>Limosilactobacillus reuteri</i> produces NMN. The NMN production yield of this species was enhanced through co-cultivation with NAD⁺-synthesizing bacteria. These findings are significant for the development of safe, NMN-enriched fermented products.