Fortification of Bioactive Compounds in Roasted Wheat Bran by Solid-State Fermentation Using Bacillus subtilis HA

Roasted wheat bran flour (RWBF) was fermented by Bacillus subtilis HA to produce bioactive compounds including mucilage and peptides. A moisture content of 60% was optimal for the solid-state fermentation, which exhibited the highest mucilage productivity after 1 day. Adding MSG to the substrate resulted in increased viable cell counts and mucilage and decreased acidity. After 1 day of fermentation, the RWBF containing 5% MSG indicated pH 6.5, mucilage content of 11.5%, consistency index of 5.59 Pa·sn, viable cell counts of 6.25 × 108 CFU/g, 4.0 mg/g tyrosine equivalents, and protease activity of 20 U/g. The total content of free amino acids tended to decrease during the alkaline fermentation, in particular, that of glutamate, indicating that the added MSG was efficiently converted to poly-γ-glutamic acid, with an 80% yield. The proposed solid-state fermentation is an effective approach to produce a highly valuable ingredient from wheat bran.