凹凸棒石对Bt蛋白的吸附特性及其对生物活性的影响

Adsorption Characteristics and Bioactivity of Bt( Bacillus Thuringiensis) Insecticidal Protein on Attapulgite

通过静态吸附实验,研究了苏云金杆菌(Bt)杀虫蛋白在凹凸棒石表面上的吸附动力学和热力学规律,考察了时间、温度、pH和蛋矿比对吸附性能的影响。研究表明:Bt杀虫蛋白能够迅速被凹凸棒石吸附,30min基本达到吸附平衡。吸附动力学对准一级、准二级、内扩散和Elovich模型的符合程度依次为:准二级模型>Elovich模型>准一级模型>内扩散模型。吸附温度升高,吸附量下降。在pH 7~10范围内,pH升高吸附量下降。初始蛋矿比升高,吸附量升高但吸附率下降。在278~318 K范围内,凹凸棒石对Bt蛋白的吸附是一个自发、放热和熵增过程。吸附自由能(△G_(ads)~0)在-35.56^-38.37 k J mol-1之间,吸附焓(△H_(ads)~0)为-16.16 k J mol^(-1),吸附熵(△S_(ads)~0)为69.47 J mol^(-1)K^(-1)。利用FTIR和XRD对吸附复合物进行了表征,提示Bt蛋白被凹凸棒石吸附后其结构没有明显变化。Bt蛋白被凹凸棒石吸附后杀虫活性提高,且抗紫外光降解能力增强,这一结果为Bt高效制剂开发和凹凸棒石的应用提供了实验依据。

Kinetics and thermodynamics for the adsorption of insecticidal protein from Bacillus thuringiensis （Bt） on attapulgite under static conditions and the influence of adsorption time, temperature, pH and the initial ratio of protein to mineral on the adsorption were studied. Results indicate that Bt protein can be adsorbed by attapulgite rapidly, and the adsorption attains equilibrium within 30 min. The fitting extent of the adsorption for pseudo-first-order, pseudo-second-order, intrapartice diffusion and Elovich model is in the order of pseudo-second-order〉Elovich〉pseudo-first- order〉intrapartiee diffusion model. The adsorption amount decrease with increasing temperature. In the range of pH from 7 to 10, the adsorption amount decrease with increasing pH values. The adsorption amount increase but the adsorption percent decrease with increasing initial ratio of protein to mineral.The adsorption of Bt protein by attapulgite is a spontaneous and exothermic process, companying increasing entropy within the temperature range of 278 - 318K. The adsorption free energy （ △Gads^0） values are between -35.56 and -38.37 kJ mol^-1 ; the adsorption enthalpy （ △Hads^0） value is 16.16 kJ mol^-1, and the adsorption entropy （△Sads^0） value is 69.47 J mo1^-1K^-1. The adsorption complex is characterized by FTIR and XRD, and the results indicate that there is no significant change of protein structure before and after adsorption. The insecticidal activity and anti-ultraviolet of Bt protein increase after being adsorbed on attapulgite. The above results provide an experimental basis for the preparation of Bt efficient formulation and the application of attapulgite.