Abstract: By culturing Aspergillus niger L., which was isolated from mouldy gardenia fruits, in broth with soybean dregs 2%, an acidic geniposide-hydrolyzing β-glucosidase was produced. When inoculated spore concentration reached to 2×10⁵/mL, the productivity was impacted significantly by both fermentation temperature and broth content. However, it was not impacted by inoculum size and rotation speed, even if the initial pH value of broth was 1.5. Under the optimal culture conditions which were fermentation temperature 28℃, initial pH value 5.5, broth content 50mL/250mL, rotation speed 150r/min and cultivation time 120h, and in the optimized medium containing soybean dregs 1%, rice bran 1% and Tween 80 0.1%, the resulting β-glucosidase activity was up to(200±10) U/mL. The activity for β-glucosidase hydrolyzing geniposide reached the maximum at pH value 2.5, the appropriate temperature 55℃ and the best hydrolysis time 15min, with K_m, V_max and half-life being 1.35g/L, 26.45g/(L·min·mg·protein) and 15min, respectively. The activity was activated by Na⁺ and Ca²⁺, and inhibited at different degrees by Mg²⁺,Ba²⁺,Cu²⁺,Fe²⁺,Hg⁺, Zn²⁺,Mn²⁺ and Hg²⁺ at 10 mmol/L, as well as inhibited by glucose and ethanol.

Key words: β-glucosidase, soybean dregs, p-nitrophenyl-β-D-glucopyranoside, genipin, Aspergillus niger L.