Studies On Hydrolysis Of Isoflavones With Bacillus Natto Glucosidase

Soybean isoflavones are composed of glucosides and aglycons. The content of aglyconsis only2~3persent. Research showes that the aglycons are of activity. Therefore, it isnecessary to convert the glucosides to aglycons. The isoflavones of fermented soybeanproduct are always in the form of aglycons under the action of microbial glucosidase. In thispaper, conditions for producing glucosidase by Bacillus natto, glucosidase properties, andhydrolyzation of isoflavones were studied.First, the conversion of isoflavones in natto was detected by thin layer chromatography(TLC). So it was certain that Bacillus natto can produce glucosidase hydrolyzing isoflavoneglucosides. It was determined to use intracellular enzyme qualitatively. By orthogonal experi-ment, optimal fermentation process was: fermentation time36h, water amount70%, inoculati-on volume10%, initial pH7.5. Under the optimal conditions, the glucosidase activity was205U/mL.The different protein components between extracellular and intracellular enzymes weredetermined by SDS-PAGE. Optimum temperature of the glucosidase was40℃, and it was ofgood thermostability. Optimum pH was5, and it had poor tolerance to strong acid and alkali.At the ion concentration of5mmol, glucosidase was activated by Na+、K+、Ca2+, but it wasinhibited by Mn2+、Cu2+. Cu2+was of highest inhibition.The hydrolysis of isoflavones was studied by orthogonal experiment. Considering the pr-actice situation, the optimum hedrolysis process was: hydrolysis temperature40℃, hydrolysistime3h, substrate concentration2mg/mL, enzyme-substrate ratio2:1. The hydrolysis rate ach-ieved84.65%at the optimal conditions. The results of HPLC showed that soybean isoflavoneglycosides were converted to isoflavone alycones with glycosidase. Genistein increasedsignificantly.