Release of bound phenol from Rosa roxburghii pomace via solid-state fermentation with Trichoderma viride: Mechanisms of change

In this study, we aimed to optimize the release of bound phenols (BPs) from Rosa roxburghii Tratt (RRT) pomace through solid-state fermentation (SSF) using Trichoderma viride and to explore the underlying mechanisms. After SSF, the polyphenol content of RRT pomace increased by 31.28% to 29.11 ± 1.77 mg gallic acid GAE/g DM. The release of BPs resulted in an increase in the content of polyphenols and free phenols, while catechins and procyanidin B2 significantly decreased. Conversely, the levels of rutin, myricetin, scopolamine, coumarin, and 3′,4′,7-trihydroxyflavones significantly increased. Enzymes, such as α-amylase, pectinase, and β-glucosidase, produced by Trichoderma viride, showed a positive correlation with the release of polyphenols throughout the SSF process. Additionally, the surface structure of the RRT pomace was altered, with the fiber surface becoming more crystalline and diluted, and certain chemical bonds broken or displaced. This study demonstrates that SSF can effectively release BPs from RRT pomace, laying the foundation for the high-value development of processing by-product resources.