Purification and identification of novel α-glucosidase inhibitors in okara fermented with Bacillus amyloliquefaciens YP2.

Background: α-Glucosidase inhibitors are established medications for managing type 2 diabetes. In this study, novel inhibitors were identified from okara fermented by Bacillus amyloliquefaciens, and their peptide-α-glucosidase interaction mechanism was investigated.

Results: The inhibition rate of α-glucosidase reached 84% ± 2% after eight dilutions when Bacillus amyloliquefaciens YP2 was used for okara fermentation. Metabolite analysis revealed abundant compounds in the fermented okara. Subsequently, 1-deoxynojirimycin (DNJ) and two additional components were purified using a combination of five types of column chromatography, with DNJ demonstrating a purity of over 95%. A total of 283 peptides were identified, of which seven were predicted as candidates using bioinformatic software and in vitro assays. The half maximal inhibitory concentration (IC₅₀) value of DNJ was 1.62 mM and that of the peptide CKLLL was 6.05 mM. Molecular docking studies indicated strong affinities of both DNJ and CKLLL for α-glucosidase, with CKLLL binding a greater number of amino acid residues.

Conclusion: This study is the first to identify diverse α-glucosidase inhibitors in fermented okara. Bacillus amyloliquefaciens YP2 is a promising strain for producing α-glucosidase inhibitors and developing hypoglycemic food as a nutritional supplement from okara. © 2025 Society of Chemical Industry.