Abstract: A higher β-glucosidase-producing strain was isolated and identified as Tolypocladium cylindrosporum syzx4 based on its morphology and internal transcribed spacer(ITS) rDNA gene sequence. The present study is to ferment, purify and characterize a β-glucosidase from T. cylindrosporum gams. The enzyme was purified to homogeneity by sulfate precipitataion, diethylaminoethyl cellulose anion exchange chromatography and Sephadex G-100 gel filtration with a 9.47-fold increase in specific activity and a recovery of 12.27%. The molecular weight(Mw) of the β-glucosidase was estimated to be 58600 by SDS-PAGE, which is much lower than that of the enzyme from other fungi. The β-glucosidase shows high activity over a wide range of temperature from 35 °C to 70 °C and the optimum pH is approximately 2.4. Then the kinetic parameters Km(0.85 mmol/L) and vmax[85.23 mmol/(L·s)] of the β-glucosidase were studied, respectively with high affinity p-nitrophenyl-β-D-glucopyranoside(p-NPG) as the substrate, inhibition constant Ki(39.5 mmol/L) with the tolerance of glucose. Although β-glucosidases have been purified and characterized from several other sources, T. cylindrosporum β-glucosidase with the unique optimal pH and higher tolerance of glucose distinguished from others makes the β-glucosidase a potential application in simultaneous saccharification and fermentation(SSF).

Key words: β-Glucosidase, Purification, Characterization, Thermoacidophilic, Tolypocladium cylindrosporum syzx4