Optimization of Aspergillus Niger fermentation for enzyme production and enzymatic hydrolysis of wheat bran for total ferulic acid via RSM

Phenolic acids in wheat bran, particularly ferulic acid (FA), exhibit antimicrobial properties, but most FA is bound to cell wall polysaccharides via ester/ether linkages, severely limiting its bioavailability and extraction. Distinct from prior studies relying on commercial enzymes or single-component substrates, this study enhanced FA release through Aspergillus niger (A. niger) fermentation (no exogenous enzymes), utilizing a wheat bran-vinegar residue (9:1, w/w) substrate. Fermentation and destarched wheat bran (DSWB) enzymatic hydrolysis were optimized via Box-Behnken design and response surface methodology (BBD-RSM), yielding high enzyme activities: feruloyl esterase (16.63 ± 0.32 U/g), xylanase (3098.21 ± 47.27 U/g), and cellulase (21.12 ± 0.14 U/g). Hydrolysis released 5.41 ± 0.03 mg/g total FA (TFA) (including derivatives), which exerted significant antibacterial activity against Escherichia coli and Staphylococcus aureus, with MIC/MBC of 0.6/2.4 mg/mL (E. coli) and 0.3/1.2 mg/mL (S. aureus). This study offers valuable data for wheat bran-derived antimicrobials and enzyme-treated bran as feed antibiotic alternatives.