Hydrolysis of soybean isoflavone glycosides by a thermostable β-glucosidase from Paecilomyces thermophila

The β-glucosidase from Paecilomyces thermophila J18 was found to be capable of hydrolysing daidzin and genistin in a previous study. This report further evaluated the thermostability and hydrolysis of soybean isoflavone glycosides. The enzyme was found to be very stable at 50 °C, and retained more than 95% of its initial activity after 8 h at 50 °C. It converted isoflavone glycosides, in soybean flour extract and soybean embryo extract, to their aglycones, resulting in more than 93% of hydrolysis of three isoflavone glycosides (namely, daidzin, genistin and glycitin) after 4 h of incubation. Also, addition of the β-glucosidase greatly increased the contents of isoflavone aglycones in the suspended soybean flour and soymilk. The results indicate that the thermostable β-glucosidase may be used to increase the isoflavone aglycones in soy products. This is the first report on the potential application of fungal β-glucosidases for converting isoflavone glycosides to their aglycones in soy products.