초록
<P><B>Abstract</B></P><P>Response surface methodology was used to optimize the medium composition to improve the production of the heat‐tolerant β‐glucosidase from <I>Bacillus</I> sp. ZJ1308. Three significant factors were found to be corn cob, beef extract, and MnSO<SUB>4</SUB>·H<SUB>2</SUB>O. The final medium compositions optimized were corn cob (51.8 g/L), beef extract (23.8 g/L), salicin (0.5 g/L), MnSO<SUB>4</SUB>·H<SUB>2</SUB>O (0.363 g/L), MgSO<SUB>4</SUB>·7H<SUB>2</SUB>O (0.4 g/L), and NaCl (5 g/L). Under the optimal conditions, the activity of β‐glucosidase was up to 4.71 U/mL. β‐Glucosidase was purified to homogeneity with a recovery rate of 5% and a specific activity of 110.47 U/mg. The optimal pH and temperature were 7.0 and 60 °C, respectively. β‐Glucosidase was stable within a pH range of 6.0–8.0 and showed an extremely high thermostability at 80 and 90 °C, retaining 56% and 38% of its maximal activity, respectively. Ni<SUP>2+</SUP> and Ba<SUP>2+</SUP> heavily inhibited the β‐glucosidase activity. The purified β‐glucosidase showed a high substrate specificity. The kinetic parameters revealed that it had a high catalytic efficiency toward the substrate <I>p</I>‐nitrophenyl‐β‐<SMALL>d</SMALL>‐glucopyranoside (<I>K</I><SUB>cat</SUB><I>/K</I><SUB>m</SUB> = 700). It also showed a high catalytic activity toward the natural substrate salicin. This study provides a new insight into the future development and use of β‐glucosidase from <I>Bacillus</I> sp. ZJ1308.</P>