Sustainable Valorization of Wheat Bran through Solid-State Fermentation and Enzymatic Bioprocessing for Enhanced Antioxidant Potential

Abstract

Trichoderma sp. RCK65, a potent polysaccharide-degrading fungal strain, was explored for its ability to enhance the antioxidant potential of wheat bran (WB) through solid-state fermentation (SSF). WB is a rich source of phenolic compounds (PCs) with notable antioxidant properties, but most are bound within the plant cell wall, limiting their bioavailability. This study compared unfermented WB (UWB), fermented WB before enzyme extraction (BE), and after enzyme extraction (AE), using various solvents to optimize phenolic extraction. The highest total phenolic content (TPC), DPPH• and ABTS•+ radical scavenging activities, and ferric reducing antioxidant potential were observed in the 70% methanol extract of BE. Even AE extracts demonstrated significantly improved antioxidant activities compared to UWB. SSF with Trichoderma sp. RCK65 also elevated free amino acid content, notably essential amino acids lysine and threonine, reinforcing its role in nutritional fortification of cereal-based foods.Further, enzymatic treatments were evaluated using commercial cellulase from Trichoderma reesei, Novozyme 188, and a crude enzyme extract of Trichoderma sp. RCK65. The crude extract led to a 3.7-fold increase in TPC (1.47 mg GAE/g WB) and the strongest enhancement in antioxidant assays: 5.3-fold (DPPH•), 2.4-fold (ABTS•+), and 2.2-fold (FRAP). UPLC analysis showed notable shifts in phenolic acid composition post-treatment, with ferulic acid (648.17 µg/g WB) as the predominant compound in enzyme-treated samples. These findings underline the superior efficacy and cost-effectiveness of Trichoderma sp. RCK65 in releasing bound phenolics, offering a promising biotechnological strategy for WB valorization and development of functional foods and nutraceuticals.