反胶束萃取α-淀粉酶动力学分析
Study on extraction kinetics of α-amylase using reversed micelles
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摘要: 利用恒界面池,在双膜理论基础上建立了CTAB-异辛烷-正丁醇反胶团体系萃取α-淀粉酶的动力学模型。考察了不同起始酶活浓度、搅拌转速、pH、液相离子强度以及表面活性剂和助表面活性剂浓度对α-淀粉酶萃取表观传质系数kL的影响并对利用改变恒界面大小在判断传质控制机理方面进行了探讨。结果表明,起始酶活浓度在1105U.L-1到4420U.L-1条件下,残酶浓度对萃取时间常用对数曲线为一直线且斜率恒定,表明该动力学方程能够较好地描述α-淀粉酶萃取过程且与初始酶活浓度在无关;搅拌转速、水相pH、水相离子强度、表面活性剂和助表面活性剂浓度对萃取过程中α-淀粉酶表观传质系数kL都有影响,从而改变传质的机制。在规定的条件下,萃取速率对恒界面相对斜率随着pH增加而减小,当pH为9.9、10.8、11.9时,萃取过程分别以界面控制、混合控制、扩算控制为主,由此可见传质速率对恒界面大小变化相对斜率可以表征界面控制的影响程度。Abstract: Based on two-film theory the kinetic model about α-amylase extraction by CTAB-n-butanol-isooctane solution as the reversed micellar extraction system was established.Varied conditions including initial enzyme activity, stirring speed, pH and ionic strength in aqueous phase, concentration of surfactant and co-solvent were performed on a stirred transfer cell with constant interface to determine the overall transfer coefficients (kL) .The relationship of control type and interfacial area was also studied.The results showed that the slope about the common logarithm of residual enzyme activity to extraction time was constant, which suggested that this kinetic model could agree with extraction process and the relationship of kL with initial enzyme activity were uncorrelated when its activity was at 1105U·L-1 to 4420U·L-1.The process of transfer mechanism was affected by the stirring speed, especially by the conditions such as pH and ionic strength in aqueous phase, and concentration of surfactant and co-solvent.The relative slope of extraction rate to interfacial area was minished contrarily with the increase of pH.Moreover, the mechanism of extraction types was mainly controlled by resistance of interface, cooperation and diffusion when pH was 9.9, 10.8 and 11.9 respectively which was performed at the appointed conditions.It also indicated that the relative slope of extraction rate to interfacial area could be used to evaluate the degree of influence of interface resistance.