Soyasaponin And Isoflavone Glycosidase In The Natto Strain Fermentation

Natto is a Japanese traditional fermented soybean food, using soybean as raw material fermented by Bacillus natto. Natto is also a micro-ecological health food, containing hundreds of kinds of physiological active ingredients needed by human. Nattokinases, soy isoflavones, soy saponins have significant biological functions.Traditional method was used for perpareing Natto, and optiaml strains were selected to fermentation. The methods of Nattokinase fermentation were identified by the optimal Bacillus natto. Bacillus subtilis protease activity assay was used to determine kinase activity, and optimal fermented conditions:the initial fermentation pH was7.0, the inoculation volume was3mL, moisture content was70%, fermentation at37℃for48h.Ethanol extraction was used to extract crude soybean isoflavone from defatted soybean meal, which main containing glycosides genistin and daidzin, and also containing free genistein and daidzein which could be detached through Sepabeads SP207macro-pore resin ethanol gradient elution.Ethanol extraction and butanol extraction were used to extract crude soybean saponin from raw defatted soybean, and AB-8macro-pore resin ethanol gradient elution was used to separation.20%ethanol concentration could elute off a very small amount of saponin, and40%and60%ethanol concentration could elute off the main saponin,80%and subsequent concentration elute off non-saponin.Soy isoflavones and soy saponins biotransfermation was also studied in natto ferment process. According to thin-layer chromatography method, the optimal culture conditions of biotransfermation were determined. The initial fermentation pH was7.0, inoculated volume was3mL, moisture content was70%,37℃fermented for48h.The extraction of glucosidase and soy saponins glucosidase and their nature was preliminary studied. Soy isoflavones glycosidase’s optimal substrate concentration was2%, the optimum reaction temperature was40℃, optimum pH value was5.0, optimum time was20h. Na+, K+, Mg2+, Ca2+activited enzyme reaction, while Fe3+, Cu2+inhibited enzyme reaction. The best soybean saponin glycosidase substrate concentration was0.5%, the optimum reaction temperature was40℃, optimum pH value was5.0, optimum time was20h. Na+, K+, Mg2+, Ca2+, Fe3+activited soybean saponin glycosidases, Cu2+inhibited soybean saponins glucosidase.