Insight into the biotransformation pathway of oat phenolic in enzyme hydrolysis coupled with Monascus fermentation

Phenolic content in oats was enhanced by enzyme hydrolysis coupled with Monascus fermentation (C-FEH). • 15 differential metabolites was identified enrich in L -phenylalanine/tyrosine pathways during C-FEH. • Possible biotransformation pathways of oat phenolics in C-FEH was revealed. Microbial fermentation and multi-enzyme systems can enhance the release and transformation of phenolic components in grains. This study constructed a system combining Monascus fermentation and multi-enzymatic hydrolysis to enrich phenolic content in oats. The mechanisms underlying phenolic release were explored using SEM, XRD, and FTIR analyses and non-targeted metabolomics was employed to investigate biotransformation pathways. Results demonstrated that the enzyme hydrolysis coupled with Monascus fermentation (C-FEH) system significantly promoted the release of oat phenolics, increasing their content from 1.05 mg GAE/g DW (unfermented) and 16.02 mg GAE/g DW ( Monascus fermentation alone) to 34.37 mg GAE/g DW. SEM and phase structure analyses revealed that C-FEH enhanced cellulose, hemicellulose, and lignin degradation, disrupting phenolic-cell wall interactions. Metabolomics identified 15 differential metabolites concentrated primarily in the L -phenylalanine and tyrosine pathways, promoting phenylpropanoid biotransformation. Phenolic bioactives such as vanillic acid, caffeic acid, p -coumaric acid, ferulic acid, naringenin, and genistein were significantly enriched. This study provides theoretical support for the functional food development of medicinal and edible grains.