Conversion of Isoflavone Glucosides to Aglycones in Soymilk by Fermentation with Lactic Acid Bacteria

Abstract

Four lactic acid bacteria (LAB), Lactobacillus paraplantarum KM, Enterococcus durans KH, Streptococcus salivarius HM and Weissella confusa JY, were isolated from humans and tested for their capabilities of converting isoflavone glucosides to aglycones in soymilk. Changes in growth, pH, and titratable acidity (TA) were investigated during fermentation at 37 degrees C for 12 h. After 6 to 9 h of fermentation, each population of 4 LAB reached 10(8) to 10(9) CFU/mL. The initial pH of 6.3 +/- 0.1 decreased while the TA of 0.13%+/- 0.01% increased as fermentation proceeded, resulting in the final range between 4.1 +/- 0.2 and 4.6 +/- 0.1 for pH and between 0.51%+/- 0.02% and 0.67%+/- 0.06% for TA after the 12 h of fermentation. The glucoside concentrations were significantly decreased in soymilks fermented with either L. paraplantarum KM, S. salivarius HM, or W. confusa JY with fermentation time (P< 0.05). L. paraplantarum KM was the best in percent conversion of glucosides to corresponding aglycones, resulting in 100%, 90%, and 61% hydrolysis of genistin, daidzin, and glycitin, respectively, in 6 h. Consequently, the aglycone concentrations in soymilk fermented with L. paraplantarum KM were 6 and 7-fold higher than the initial levels of daidzein and genistein, respectively, after 6 h of fermentation. Changes in the daidzin and genistin levels were not significant in soymilk fermented with E. durans KH. The rates of hydrolysis of glucosides varied depending on the species of LAB. Especially, L. paraplantarum KM seems to be a promising starter for bioactive-fermented soymilk based on its growth, acid production, and isoflavone conversion within a short time.

Production of Liquiritigenin with Cell-based Biotransformation and Its Anti-Aging Activity

“…For example, β-glucosidase produced by Ganoderma lucidum and lactic acid bacteria can convert isoflavone glucosides into aglycones in soymilk [9,13]. Indeed, the maximal level of β-glucosidase activity during L. sulphureus CS0218 fermentation was approximately 8.6 U/mL.…”

“…It is known that glycosidases can catalyze the hydrolysis of glycosidic linkages or glycoside units in predominant isoflavone glucosides or carbohydrate oligomers [9,11,28]. Therefore, we tested whether some of glycosidases produced by L. sulphureus CS0218 during fermentation are capable of converting glucosides to aglycones with high conversion activity.…”

“…There are several studies on their beneficial effects including prevention of carcinogenesis [6,7], hepatoprotective effects [1], and anti-inflammatory effects [4]. Recent studies also demonstrated that aglycones are digested much faster and enhanced their functions than their corresponding glucosides in humans [8,9]. In particular, the glucosides do not easily digest and absorb completely in intestinal epithelial cells in humans.…”

“…In particular, the glucosides do not easily digest and absorb completely in intestinal epithelial cells in humans. Therefore, the hydrolysis of the isoflavone glucosides is necessary to increase their absorption in the intestine and promote health related beneficial effects [9,10]. So, much effort has been devoted to develop an efficient and simple enzymatic bioconversion method instead of the harsh chemical treatment [9,[11][12][13].…”

“…Some hydrolyzing enzymes including glucanase and xylanase have been produced from various mushrooms and characterized [14,26,27]. Among them, β-glucosidase can be efficiently used for the hydrolysis of glycosidic bonds, acetylglycoside or malonylglycoside to increase the concentration of bioactive aglycones [9,11,28,29].…”