Talaromyces thermophilus β-d-Xylosidase: Purification, Characterization and Xylobiose Synthesis

Abstract

When grown on wheat bran as the only carbon source, the filamentous fungus Talaromyces thermophilus produces large amounts of β-xylosidase activity. The presence of glucose drastically decreases the β-xylosidase production level. The β-xylosidase of T. thermophilus was purified by ammonium sulfate precipitation, DEAE–cellulose chromatography, and gel filtration (high-performance liquid chromatography). The molecular mass of the enzyme was estimated to be 97 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis and gel filtration. The enzyme activity was optimum at 50 °C and pH 7. The apparent Michaelis constant K _m of the β-xylosidase was 2.37 mM for p-nitrophenyl-β-d-xylopyranoside, with a V _max of 0.049 μmol min⁻¹ per milligram protein. Enzyme activity was inhibited by Cu²⁺, Hg²⁺, and Zn²⁺ and activated by Ca²⁺, Mn²⁺, and Co⁺ at a concentration of 5 mM. At high xylose concentration, this enzyme catalyses the condensation reaction leading to xylobiose production.