Hydrolysis of soybean isoflavone glucosides by lactic acid bacteria

Lactobacillus delbrueckii subsp. delbrueckii KCTC 1047, grown in de Man, Rogosa and Sharpe (MRS) or soymilk media, completely hydrolyzed the isoflavone glucosides, genistin and daidzin at 50 g ml^–1, into their respective aglycones, genistein and daidzein within 30 min. Other lactic acid bacteria did not produce -glucosidase, the enzyme responsible for the hydrolysis of isoflavone glucosides, when cultured in MRS medium. Glucoside-hydrolyzing activity was induced in some lactic acid bacteria when cultured in soymilk medium. These strains hydrolyzed 70–80% of genistin into genistein and 25–40% of daidzin into daidzein.