<i>Lactiplantibacillus plantarum</i> Fermentation Enhances the Bioactivity of Polymeric Proanthocyanidins: Gut Microbiota Regulation via Caffeic Acid Production

Polymeric proanthocyanidins (PPC) typically exhibit low bioavailability. While probiotic metabolism can enhance polyphenol bioactivity, the interaction between <i>Lactiplantibacillus plantarum</i> and PPC remains underexplored. In this study, <i>L. plantarum</i> SFFI23, a strain exhibiting excellent capacity to metabolize PPC, was selectively isolated. During <i>in vitro</i> digestion and fecal fermentation, SFFI23 reduced the degree of polymerization of PPC and enhanced overall antioxidant capacity. Metagenomic analysis revealed that SFFI23-PPC metabolism resulted in <i>Firmicutes</i> enrichment, accompanied by opportunistic pathogen reduction and an upregulation of health-associated pathways such as quorum sensing. Metabolomics analysis showed significant enrichment in 17 metabolic pathways. Multiomics analyses revealed that caffeic acid, derived from SFFI23-PPC metabolism, contributes to improved gut health by regulating gut microbiota and promoting metabolic reprogramming. This study outlines a triadic mechanism: "biotransformation by <i>L. plantarum</i>-metabolic activation of PPC-gut microbiota regulation", highlighting the potential of SFFI23 as an adjunct for enhancing PPC bioactivity.