Bioconversion of Soybean Isoflavone by Lactobacillus plantarum and Bifidobacterium longum

Abstract In this study, phytoestrogen for the industrial production of soybean probiotics by lactic acid bacteria (LAB) was studied in a soybean extract. Soybean was fermented with LAB, Lactobacillus plantarum KCTC 3108 and Bifidobacterum longum ATCC 15707. The change in the content of various isoflavones (aglycone and glucoside) and the β-glucosidase activity in soybean during fermentation were investigated and shown to be dependent on the starter organism. Soybean extract powder fermented with L. plantarum showed the highest β-glucosidase activity and the greatest increase in the aglycone content. After 48h of fermentation, the contents of daidzin, genistin and glycitin in L. plantarum decreased from a mean initial levels of 83.03±2.17, 168.13±8.17 and 20.02±1.07, respectively, to mean levels of 5.34±3.24, 3.79± 0.57 and 1.87±1.09 mg/100 g. Whereas, after 48h fermentation, the contents of daidzein, genistein and glycitein increased from a mean initial levels of 8.09±0.78, 11.20±0.84 and 4.71±0.46, respectively, to mean levels of 85.76±0.84, 175.87± 2.21 and 22.41±0.91 mg/100 g. Taken together, these results suggested an increase of aglycones and decrease of glu-coside in isoflavones occurred during fermentation, which coincided with an increase of β-glucosidase activity in the fermented soybean extract powder.