Hydrolysis of isoflavones and consumption of oligosaccharides during lactic acid fermentation of soybean milk

Aiming to select suitable strains of lactic acid bacteria for producing yogurt-like functional food from soybean milk, the fermentation properties of 14 lactic acid bacterial strains belonging to genera Bifidobacterium, Lactobacillus, Lactococcus and Streptococcus were evaluated using soybean milk as the culture medium. All 14 strains examined were able to grow in soybean milk, Twelve out of the 14 strains lowered the pH of the medium and produced lactic acid. Tested strains showed a variety of consumption patterns of oligosaccharides and hydrolyzing capacity of isoflavone glucosides. Three strains, Bifidobacterium breve JCM 1192, B. bifidum JCM 1255 and Lb. casei subsp. rhamnosus IFO 3425 exhibited the most promising results. These strains could hydrolyze both daidzin and genistin to corresponding aglycones, and consume raffinose and stachyose in addition to lowering the pH and producing lactic acid.