# Mechanistic insights into Grifola frondosa-driven fermentation of Rice-wheat bran: Metabolomic profiling, molecular dynamics, and enhanced antioxidant efficacy

## TL;DR

This study shows that fermenting rice and wheat bran with Grifola frondosa boosts bioactive compounds and antioxidant effects, making it a promising functional food ingredient.

## Contribution

The study introduces a novel fermentation method using Grifola frondosa to enhance the bioaccessibility and antioxidant properties of rice-wheat bran.

## Key findings

- Fermentation increased polysaccharide, polyphenol, and protein contents significantly after 13 days.
- Metabolomics identified 445 differentially expressed metabolites, with ferulic acid methyl ester highly upregulated.
- FRBWB showed improved antioxidant activity and reduced oxidative stress in zebrafish embryos.

## Abstract

Rice bran (RB) and wheat bran (WB) are rich in bioactives but poorly utilized due to limited bioaccessibility. Here, a fungal fermentation strategy was developed to valorize RB-WB blends. A novel fermented product (FRBWB) was obtained via Grifola frondosa (G. frondosa) fermentation, with conditions optimized for bioactive enrichment. After 13 days of fermentation, polysaccharide, polyphenol, and soluble protein contents increased from 86.56 to 126.93 mg/g, 1.38 to 1.67 mg/g, and 53.69 to 93.06 mg/g, respectively (P < 0.05), accompanied by marked improvements in water-holding capacity and solubility. The process altered substrate's microstructure, resulting in a looser, more porous surface. Untargeted metabolomics identified 445 differentially expressed metabolites (DEMs) between FRBWB and the unfermented control (RBWB), among which ferulic acid methyl ester showed the highest upregulation. Molecular docking and molecular dynamics simulations suggested a stable interaction between ferulic acid methyl ester and lignin peroxidase, dominated by van der Waals forces, electrostatic interactions, and hydrogen bonding (ΔEMMPBSA = −79.73 ± 1.47 kJ/mol), which may help rationalize the observed enhancement of phenolic release. Functionally, FRBWB exhibited significantly enhanced in vitro antioxidant activity and conferred superior protection against AAPH-induced oxidative stress in zebrafish embryos, improving survival (92% at 50 μg/mL), hatching rate (87.69%), and reducing reactive oxygen species (ROS), apoptosis, and lipid peroxidation (P < 0.05). Overall, this study suggests that G. frondosa fermentation represents a sustainable strategy for upgrading RB–WB by-products into functional food ingredients with potential antioxidant benefits.

•A novel rice-wheat bran fermented product was developed by Grifola frondosa.•A 13-day fermentation enhanced bioactive contents, functional properties, and formed a porous low-crystallinity structure.•Metabolomics uncovered 445 differential metabolites with ferulic acid methyl ester highly upregulated.•Molecular dynamics revealed a stable binding of ferulic acid methyl ester to lignin peroxidase.•The product alleviated oxidative stress in zebrafish through multiple antioxidant pathways.

A novel rice-wheat bran fermented product was developed by Grifola frondosa.

A 13-day fermentation enhanced bioactive contents, functional properties, and formed a porous low-crystallinity structure.

Metabolomics uncovered 445 differential metabolites with ferulic acid methyl ester highly upregulated.

Molecular dynamics revealed a stable binding of ferulic acid methyl ester to lignin peroxidase.

The product alleviated oxidative stress in zebrafish through multiple antioxidant pathways.