Transcriptome-guided engineering of a native niacin transporter in unveils metabolic rewiring for NMN biosynthesis.

INTRODUCTION

β-nicotinamide mononucleotide (NMN), a precursor of NAD, holds promise as a functional food ingredient for mitigating age-related decline. This study enhanced NMN biosynthesis in probiotic .

METHODS

A putative niacin transporter, , was identified via molecular docking and validated by CRISPR/Cas9. A dual-copy expression strategy was also employed to increase NMN production. In parallel, RNA-seq was used to analyze genome-wide transcriptional changes associated with enhanced NMN biosynthesis.

RESULTS

Overexpression of increased NMN production by 62.3%, and a dual-copy strategy raised NMN titers to 203 μmol L-269% increase compared to empty-vector control without NAM and the highest yield reported in lactic acid bacteria. Transcriptomic analysis revealed 598 differentially expressed genes, including upregulated ribosomal proteins () and NAD salvage enzymes (), indicating enhanced translation and precursor flux. Deleting , encoding a metabolic constraint, further boosted NMN levels, confirming transcriptomic predictions.

DISCUSSION

This combined transporter engineering and transcriptome-guided strategy establishes a food-grade platform for efficient NMN production in functional fermented foods.