Food Microorganisms that Effectively Hydrolyze O‐Glycoside but Not C‐Glycoside Isoflavones in Puerariae Radix

Puerariae radix (PR) is known to contain abundant glucoside conjugates of daidzein isoflavones. This study was performed to determine the daidzin hydrolysis activity of the various strains of probiotic bacteria and edible fungi during fermentation of PR. Among the strains tested, Bifidobacterium sp. Int‐57 showed the greatest β‐glucosidase activity and daidzin hydrolysis activity. When yeast extract (2.5%) was added to the PR medium during fermentation with Bifidobacterium sp. Int‐57, all of the daidzin was hydrolyzed to near completion. The addition of skim milk and whole milk also improved the conversion of daidzin into daidzein. Puerarin, a C‐glucoside of daidzein in PR, was not hydrolyzed into daidzin by any of the experimental strains during fermentation. This study demonstrates that daidzin can be efficiently converted into daidzein by the proper combination of probiotic strains and fermentation conditions.