Conversion of isoflavone glycoside to aglycones in soy protein isolate (SPI) using crude enzyme extracted from Bifidobacterium animalis Bb12 and Lactobacillus delbrueckii ssp. Bulgaricus ATCC 11842

Abstract

Crude enzyme extracts from B. animalis Bb12 and L. delbrueckii ssp. bulgaricus ATCC 11842 were used at 0.1, 0.5, and 1.0 g/L to hydrolyse glycitin (isoflavone glycosides) to its biologically active form (isoflavone aglycones; IA) in soymilk (SM) prepared from soy protein isolate (SPI) supplemented with 2.0% (w/v) of D-glucose. Enumeration of microbial populations, measurement of pH and quantification of isoflavones was carried out at 0 h, 6 h and 12 h of fermentation. The quantification of isoflavone compounds in SM was carried out using HPLC. The biotransformation of glycitin was higher at the enzyme level of 1.0 g/L from B. animalis Bb12 at 12 h than that at 0.5 g/L or 0.1 g/L, and the level of biotransformation was 74.4%, while 75.23% of glycitin was biotransformed with the enzyme extracted from L. delbrueckii ssp. bulgaricus ATCC 11842 at the same level of enzyme. The decrease in pH by B. animalis Bb12 was lowest with 1.0 g/L and highest with the control (4.69). Similarly, the decrease in pH by L. delbrueckii ssp. bulgaricus ATCC 11842 was lowest with 1.0 g/L (5.19) and highest with the control (5.86). The final viable population of the B. animalis Bb12 ranged from 5.94 to 7.49 log CFU/mL and that of L. delbrueckii ssp. bulgaricus ATCC 11842 ranged from 4.42 to 6.70 log CFU/mL and the organisms showed the highest viable population of 6.70 log CFU/mL at 12 h with 1.0 g/L crude enzyme.