Abstract:

Bacterial fermentation was employed to convert glycoside isoflavones in soybean milk into aglycone ones (free isoflavones that mainly consist of daidzein and genistein) to enhance their bioavailability. The optimal bacterial strain was screened from 11 strains in terms of the concentrations of daidzein and genistein in fermented soybean milk that were determined by high performance liquid chromatography (HPLC) and its fermentation conditions were optimized for maximizing the concentration of free isoflavones using the single-factor method combined with a quadric regression orthogonal rotation design. Both the contents of daidzein and genistein in soybean milk fermented by Lactococcus lactis subsp. cremoris were the highest and the optimum fermentation conditions of this strain for converting glycoside isoflavones were determined as follows: fermentation for 28 h at 41 ℃ with inoculation amount of 4%.

Key words: Lactobacillus, fermentation of soybean milk, daidzein, genistein