Screening and Optimization of α-Glucosidase Inhibitor Production by Potent Strain of Bacillus subtilis Isolated from Peruyaan, Fermented Soy-Food of Northeast India

Background. Fermented soy foods exhibit the capability to inhibit the α-glucosidase enzyme. The bacteria isolated from these fermented soy foods may contribute to the production of a higher quantity of α-glucosidase inhibitor (α-GI) in optimized condition. Aim. The present study aims to isolate α-glucosidase inhibitor producing bacterial strain from peruyaan, a traditional fermented soy food of Arunachal Pradesh, optimize the production of α-GI for maximum yield, and assess the compounds. Result. Bacillus subtilis PM NEIST_4 (identified by 16S rRNA gene sequencing) was isolated as a potential strain that exhibit maximum α-glucosidase inhibition. This strain showed maximum α-GI productivity in Mueller Hinton Broth (MHB). The cultivation parameters for fermentation of MHB were optimized in order to maximize the yield of α-GIs. The α-GI productivity of 1616.613 ± 84.54 U/mL was observed before optimization, which increased by almost three times after optimization (4808.324 ± 13 U/mL). In vitro assays against α-glucosidase enzyme revealed a significant IC50 value of 596.532 ± 44.80 μg/mL after the optimized study compared to that before optimization (IC50 1705.617 ± 43.95 ug/mL). Besides, α-glucosidase enzyme inhibitory property of fermented MHB (FMHB) was found to be unaffected at varied range of pH and temperature. Oral gavaging of FMHB in sucrose-loaded Wistar rat exhibited maximum reduction in postprandial blood glucose at 400 mg/kg body weight. Furthermore, FMHB was fractionated using solvents of increasing polarity including n-hexane, ethyl acetate, and n-butanol. Ethyl acetate fraction that exhibited the strongest inhibitory action against the α-glucosidase enzyme (IC50 value of 251.55 ± 19.65 μg/mL), showed the presence of pyrrolopyrazine derivatives through GC-MS and LC-MS analyses. Conclusion. The present study demonstrated the isolation of a potent α-GI producing bacterial strain from traditional fermented soy food, and the optimization of the bacterial fermentation process was achieved to maximize the yield of α-GI. These findings underscore promising industrial potential of B. subtilis PM NEIST_4, advocating the use of indigenous microbial resources for the production of α-GI.