Abstract:

In order to investigate the effects of surfactants and ionic liquid 1-ethyl-3-methylimidazolium phosphate ([EMIM]DEP) on the activity of β-glucosidase of Paenibacillus sp. LLZ1, a certain concentration of surfactants and [EMIM]DEP were added to the enzyme activity assay system. The results showed that the addition of 5% [EMIM]DEP enhanced the activity of β-glucosidase by 12.00%, and the further addition of 0.1% rhamnolipid, Span20, PEG4000 and Tween80 increased by 21.85%, 12.07%, 8.57% and 5.25%, respectively, while Triton X-100 and SDS reduced β-glucosidase activity by 4.59% and 10.63%. The kinetic curves and kinetic parameters indicated that with the increase of the β-glucosidase activity within the 0.1% surfactants and 5% [EMIM]DEP, the Michaelis constant K_m decreased. Circular dichroism spectroscopy showed that the α-helix of β-glucosidase increased by 1.00%, 0.78%, 0.72%, and 0.80% after treatment with 0.1% rhamnolipid, Span20, PEG4000, and Tween80, respectively. Adding SDS resulted in a sharp decrease in the α-helix content by 5.72%. Fluorescence spectroscopy indicated that the maximum emission wavelength of β-glucosidase was altered in the presence of surfactants and 5% [EMIM]DEP. Differential scanning calorimetry showed that 0.1% hamnolipid and 5% [EMIM]DEP changed the midpoint temperature and the average unfolding enthalpy of β-glrucosidase. When the hydrolysis of cellobiose was carried out using 0.1% rhamnolipid in combination with 5% [EMIM]DEP, the conversion rate was improved by 21.93%.

Key words: cellobiose, β-glucosidase, ionic liquid, surfactant, fluorescence spectrum

摘要：

为考察表面活性剂和离子液体1-乙基-3-甲基咪唑磷酸二乙酯盐（[EMIM]DEP）对类芽孢杆菌sp. LLZ1 β-葡萄糖苷酶活性的影响，在酶活测定体系中加入一定浓度的表面活性剂和[EMIM]DEP。结果表明：添加5%的[EMIM]DEP使β-葡萄糖苷酶的活性增强了12.00%，进一步添加0.1%鼠李糖脂、Span20、PEG4000和Tween80分别使酶活增强了21.85%、12.07%、8.57%和5.25%，而Triton X-100和SDS分别使酶活降低了4.59%和10.63%。动力学曲线和动力学参数表明随着表面活性剂和5%[EMIM]DEP对β-葡萄糖苷酶活性的增强，米氏常数K_m随之减小。圆二色谱（CD）分析表明分别经0.1%鼠李糖脂、Span20、PEG4000和Tween80处理后，β-葡萄糖苷酶的α-螺旋分别增加1.00%、0.78%、0.72%和0.80%，添加SDS导致α-螺旋减少5.72%。荧光光谱表明同时添加表面活性剂和5%[EMIM]DEP改变了β-葡萄糖苷酶的最大发射波长。差示扫描量热法(DSC)表明0.1%鼠李糖脂和5%[EMIM]DEP提高了β-葡萄糖苷酶的中点温度和平均展开焓。使用0.1%鼠李糖脂协同5%[EMIM]DEP水解纤维二糖，转化率提高了21.93%。

关键词: 纤维二糖, β-葡萄糖苷酶, 离子液体, 表面活性剂, 荧光光谱