Full Length Research Paper

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

Bin Qi^1,2, Limei Wang², and Xianjin Liu¹*

¹Food Safety Research and Service Center, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, P. R. China.

²Department of Biotechnology and Food Engineering, Changshu Institute of Technology, Changshu 215500 P. R. China.

*Corresponding author. E-mail: qibin_js@yahoo.com. Tel. /Fax: 025-84390396.

Accepted 10 February, 2009

Aspergillus sp. MT-0204, a novel strain for producing β-glucosidase, was isolated from soil in this study. The β-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 β-glucosidase was purified in four steps. Some characteristics of purified β-glucosidase were also studied. The β-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°C, and significantly at 85°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-Na₂ and fumarate.

Key words: Aspergillus niger MT-0204, β-glucosidase, characterization, isoflavones, soybean.