Enhancing small peptide content and improving the microbial community and metabolites in corn gluten meal with solid-state fermentation using keratinase-producing Bacillus strains

Corn gluten meal is recognized as a potential source of high-quality plant-derived proteins. The enhancement of its protein quality can be accomplished through the incorporation of keratinase during solid-state fermentation. However, the widespread application of keratinase is constrained by its high production costs. In this study, two Bacillus strains capable of producing keratinase were isolated. Compared to separate fermentation processes, B. subtilis LDJ01 and B. siamensis LDJ02 mixed bacteria solution (SS) fermentation could more efficiently degrade large proteins in the corn gluten-wheat bran mixture (CGW). After fermentation, the small peptide content of the CGW was significantly increased and the SS showed the potential to replace keratinase. Moreover, the addition of SS improved the nutritional value and changed the overall odor of the CGW. Furthermore, the SS could inhibit the growth of pathogenic bacteria including Pantoea and Pseudomonas in the CGW, while promoting the enrichment of beneficial metabolites such as SCFAs, glutathione, lithocholic acid and lactobionic acid during fermentation. Notably, the fermentation process of the CGW primarily involved changes in amino acid and lipid metabolic pathways. Overall, this study provides a feasible solution for the development of plant-based protein resources.