Purification and characterization of β-glucosidase from newly isolated Aspergillus sp MT-0204

Aspergillus sp. MT-0204, a novel strain for producing beta-glucosidase, was isolated from soil in this study. The beta-glucosidase can hydrolyze glycosides and increase free isoflavones in soy products isoflavones. By examining physiological, biochemical characteristics and comparing its ITS rDNA gene sequence, it was identified as Aspergillus niger, and named A. niger MT-0204. The A. niger beta-glucosidase was purified in four steps. Some characteristics of purified beta-glucosidase were also studied. The beta-glucosidase activity could be assayed at the pH ranging from 3.5 to 10.0, and its maximum activity was obtained between pH 5.0 and 5.5. The enzyme was sensitive to heat, decreasing slowly between 60 and 80 degrees C, and significantly at 85 degrees C. The enzyme activity was activated by K+, Ca2+, Fe2+, Mg2+ and Mn2+, while strongly inhibited by Ag+ and Hg+, and slightly inhibited by Cu2+, Zn2+, Ba2+, Ni+, EDTA-Na-2 and fumarate.