The expression of β-glucosidase during natto fermentation increased the active isoflavone content

Abstract

Natto is a traditional food fermented by Bacillus subtilis natto with soybean as raw material and contains a variety of active substances, especially flavonoid. Flavonoids in soybean usually exist in the form of inactive glycosides, which can only play biological activities when being decomposed into free isoflavone aglycone by β-glucosidase. In this study, the relationship between the activity of β-glucosidase, the expression of β-glucosidase coding genes and the content and structure of active isoflavones in Bacillus natto was systematically elucidated for the first time. In this research, more than 70 kinds of flavonoids have been identified and the active isoflavones in natto increased by 2.2 times compared with soybeans. Furthermore, the activity of β-glucosidase and the expression level of its coding genes were both increased, which laid a theoretical foundation for further understanding the active substances and physiological functions of natto and the application of β-glucosidase in food industry.