Functional beverage from fermented soymilk with improved amino nitrogen, beta-glucosidase activity and aglycone content using Bacillus subtilis starter

Abstract

The bioactivity of soymilk was enhanced by fermentation with three strains of beta-glucosidase-producing Bacillus subtilis for 36 h at 37 degrees C. The results indicated that protease, cellulase, and beta-glucosidase activities were significantly (p<0.05) increased with increasing fermentation time. In addition, the amino-type nitrogen content in B. subtilis-fermented soymilk was increased to 121.1-140.7 mg% after 36 h of fermentation. Among the isoflavones in soymilk, the contents of beta-glucosides or acetyl-glucosides were decreased, while aglycone content was increased by fermentation. In particular, the soymilk fermented with B. subtilis HJ18-9 had highest beta-glucosidase activity and the largest increase in aglycone content. The total aerobic and anaerobic cell counts were increased with increasing fermentation time. Therefore, this study suggests that soy beverages fermented with beta-glucosidase-producing B. subtilis have the potential to enhance the health and nutritional status of consumers.