Production of β-glucosidase from okara fermentation using Kluyveromyces marxianus

The effective utilization of okara (soybean residue) has become a considerable challenge in recent years. In this paper, the potential advantages of β -glucosidase production from okara fermented by Kluyveromyces marxianus were evaluated and the properties of the β -glucosidase were also characterized. The results showed that okara can significantly induce the production of β -glucosidase from K. marxianus . The β -glucosidase activity was up to 4.5 U/mg under optimized fermentation conditions. The optimal parameters were as follows: fermentation temperature 35 °C, cultivation time 98 h, inoculum concentration 10%, and 30 g/L of okara. After two steps of purification using ammonium sulfate precipitation and Sephadex G-75 column chromatography, the activity of β -glucosidase was 71.4 U/mg. The native enzyme was an approximately 66 kDa dimer consisting of two different subunits (22 and 44 kDa). The kinetic parameters of the K. marxianus β -glucosidase, using p NPG as substrate, were V max 8.34 μmol min −1 mg −1 and K m 7.42 mM. The β -glucosidase showed high thermostability and acid–alkali tolerance as well as low inhibition by DMSO (10–50%). In conclusion, this study supports the notion that okara fermentation by K. marxianus could be a useful process to produce β - glucosidase .