Microbial Whole-Cell Biocatalysis for Phloretin Production from Naringenin

Phloretin, a dihydrochalcone with pharmaceutical and nutraceutical applications, is traditionally extracted from plants with limited efficiency. In this study, we report a bioconversion pathway for phloretin production from naringenin in <i>Lactobacillus plantarum</i>. The biosynthetic route was established by screening heterologous iron-sulfur cluster-containing enoate reductases and coexpressing flavin reductases and formate dehydrogenases, which provided dual NADH-FAD cofactor regeneration. Promoter engineering, along with the targeted overexpression of iron uptake genes and optimized iron concentrations, increased the phloretin titer. Structure-guided semirational design of enoate reductase identified the D656R mutant, and a phloretin titer of 70.53 mg/L was achieved, representing the first report of flavonoid biosynthesis in <i>L. plantarum</i>. This work offers <i>L. plantarum</i> as a promising host for the production of phloretin and its derivatives.