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

The beta-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 degrees C, and retained more than 95% of its initial activity after 8 h at 50 degrees 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 beta-glucosidase greatly increased the contents of isoflavone aglycones in the suspended soybean flour and soymilk. The results indicate that the thermostable beta-glucosidase may be used to increase the isoflavone aglycones in soy products. This is the first report on the potential application of fungal beta-glucosidases for converting isoflavone glycosides to their aglycones in soy products. (C) 2009 Elsevier Ltd. All rights reserved.