Enhancing antioxidant activity of corn bract and silk juices through biotransformation of polyphenols by Lactobacillus paracasei TJ199 fermentation

TJ199 - a strain with exceptional antioxidant capacity - was used to ferment corn bract juice (CBJ) and silk juice (CSJ). Fermentation increased total phenolic (0.47 - and 0.23 - fold) and flavonoid contents in CBJ and CSJ, respectively. Antioxidant activity was significantly enhanced, particularly in DPPH (increased by 0.34 and 0.38 - fold), ABTS (increased by 2.76 and 1.40 - fold) scavenging activity, and FRAP (increased by 3.67 and 2.22 - fold). Widely targeted metabolomics identified 348 phenolic compounds, including butin, curcumin, demethoxycurcumin, they primarily enriched in flavonoid and anthocyanin biosynthesis pathways, and underwent TJ199 - mediated structural modifications (including hydroxylation, deglycosylation, and seven other reactions). Upregulated phenolic products (butin) exhibited stronger antioxidant activity than precursors (liquiritigenin) after biotransformation. These findings provided insights for developing corn bract and silk as food ingredients.