Overexpression of β-glucosidase from Thermotoga maritima for the production of highly purified aglycone isoflavones from soy flour

To produce aglycone isoflavones from soy flour, the β-glucosidase A gene (bglA) of Thermotoga maritima was overexpressed in Escherichia coli BL21-CodonPlus (DE3)-RIL. The K m and V max values of the purified BglA for pNPG were 0.43 mM and 323.6 U mg⁻¹, respectively, and those for salicin were 9.0 mM and 183.2 U mg⁻¹, respectively. The biochemical and kinetic characteristics of his-tagged BglA were found to be similar to those of BglA, except for the temperature stability and specific activity. Production of aglycone isoflavones from soy flour by BglA was examined by HPLC. For 3 h at 80°C, all the isoflavone glycosides approximated to the complete conversion into aglycone isoflavones, over seven times higher than that obtained from soy flour without BglA.