Abstract
In this work, a new strain of Bacillus amyloliquefaciens SY07 isolated from a traditional fermented soybean food was reported to possess remarkable α-glucosidase inhibitor-producing ability. Different culture media were applied for the proliferation of B. amyloliquefaciens SY07, and it was found that fermented okara broth presented the highest α-glucosidase inhibitory activity, while Luria-Bertani medium showed a negative effect. The extract from fermented okara broth acted in a dose-dependent manner to inhibit α-glucosidase activity, with an IC50 value of 0.454 mg/mL, and main inhibitors in the fermentation extract presented a reversible, uncompetitive pattern according to Lineweaver–Burk plots. Moreover, 1-deoxynojirimycin, a recognized α-glucosidase inhibitor, was found in the extract. Results indicated that B. amyloliquefaciens SY07 could utilize okara, a by-product from the soy processing industry, to generate α-glucosidase inhibitors effectively, and be regarded as a novel excellent microbial candidate for safe, economical production of potential functional foods or ingredients with hypoglycemic effect.
Highlights
Diabetes mellitus, a metabolic disorder characterized by chronic hyperglycemia and accompanied by a number of severe complications, is a worldwide epidemic. α-Glucosidase (EC 3.2.1.20), present in the small intestinal brush border, can catalyze the transformation of complex carbohydrates into glucose suitable for absorption [1]
Compared to the MS–MS spectrum of the standard DNJ, the fragment ion information of the MS 2 of the sample was almost the same as the standard DNJ, which further indicated that the generation of DNJ in the fermented okara broth started with B. amyloliquefaciens SY07
A newly isolated strain B. amyloliquefaciens SY07 was found capable of producing α-glucosidase inhibitors in certain culture media
Summary
A metabolic disorder characterized by chronic hyperglycemia and accompanied by a number of severe complications, is a worldwide epidemic. α-Glucosidase (EC 3.2.1.20), present in the small intestinal brush border, can catalyze the transformation of complex carbohydrates into glucose suitable for absorption [1]. No α-glucosidase inhibitory activity was observed in the fermentation broth of LB medium. When B. amyloliquefaciens SY07 was cultured in LB medium supplemented with soy powder or okara, the α-glucosidase inhibitory activities of the broths were significantly (p < 0.05) weaker than that fermented in sole soy powder or okara culture, respectively. The sample, fermented okara broth extract (FOBE), which possessed the strongest α-glucosidase inhibitory activity was subjected to further analysis of inhibition properties. Compared to the MS–MS spectrum of the standard DNJ, the fragment ion information of the MS 2 of the sample was almost the same as the standard DNJ, which further indicated that the generation of DNJ in the fermented okara broth started with B. amyloliquefaciens SY07. The enriched culture was diluted with sterile distilled water to prepare the starter suspension with a concentration of around 107 cfu/mL
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