Isoflavone phytoestrogens in soymilk fermented with β-glucosidase producing probiotic lactic acid bacteria.

Isoflavones significantly contribute to human health and disease prevention, and exist as glucosides and aglycones. The β-glucosidase enzyme that hydrolyzes glucosides to aglycones is very sensitive to molecular structure, and thus the profile of the isoflavones can affect their rate of hydrolysis. Soymilk was fermented with Lactobacillus acidophilus B4496 (La), Lactobacillus bulgaricus CFR2028 (Lb), Lactobacillus casei B1922 (Lc), Lactobacillus plantarum B4495 (Lp) and Lactobacillus fermentum B4655 (Lf) for 48 h at 37°C. β-Glucosidase activity was determined using p-nitrophenyl β-D-glucopyranoside as a substrate and the hydrolysis was carried out in soymilk. During fermentation, maximum growth was seen at 24 h with Lb, Lc, Lp and Lf and at 48 h with La. Polyphenol content ranged from 12.98 to 17.90 at 24 h and from 12.44 to 15.24 mg/100 ml at 48 h of fermentation. All the lactic acid bacteria produced β-glucosidase enzyme, which hydrolyzed isoflavone glucosides to aglycones at a significant level (P < 0.05) in the fermented soymilk.