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解结晶对纤维素吸附纤维素酶的影响

Effect of Decrystallization of Cellulose on Adsorbing Cellulase

  • 摘要: 为探讨解结晶处理提高酶水解效率的机理,对比研究了高结晶度的微晶纤维素(MCC)和低结晶度的解结晶微晶纤维素(D-MCC)对纤维素酶的吸附过程。结果发现:酶吸附平衡后,样品的XPS和FT-IR分析表明纤维素酶通过酶蛋白的氨基(-NH2)与纤维素分子链上的羟基(-OH)之间以氢键(C-OH…NH)力吸附在MCC上;相同条件下得到的MCC和D-MCC吸附率曲线的差异表明,底物结构的改善比提高温度更能提高酶吸附率;比较纤维素酶对MCC和D-MCC在35℃下的吸附动力学可知,通过降低底物的结晶度可促进酶吸附,刚性结构的MCC更满足准一级动力学的假设,D-MCC表面结构相对松散,其吸附过程需进一步分析,以得到更适合的动力学方程。

     

    Abstract: The cellulase adsorbed and formed enzyme-substrate(ES) compound is a key step in the process of enzymatic hydrolysis.Through the comparison of cellulase adsorbed on two substrates: microcrystalline cellulose(MCC) with high degree of crystallinity and decrystallization microcrystalline cellulose(D-MCC) with low degree of crystallinity, it was found that, in the XPS wide scan patterns of adsorption equilibrium MCC, a new absorption peak of nitrogen element(399.06 eV) was observed.The fitting method is adopted to treat the strong peak of XPS-O1s, and the binding energy of this new peak was only 530.53 eV.In the infrared absorption range of 3050-3550 cm-1, the absorption intensity of OH group decreased with extending adsorption time on cellulose.The above results proved that new hydrogen bonds (C-OH…NH) between the protein amino(-NH2) and cellulose molecule chain(-OH) were generated during the cellulose adsorption process.From the comparison of the adsorption rate curves between MCC and D-MCC, the decrystallization method to improve cellulase adsorption was more effective than enhancing the temperature.From the comparison of adsorption kinetics between MCC and D-MCC at 35℃, it was indicated that a reduction of cellulose crystallinity was positive for adsorption rate.MCC with rigid surface was fit for the first-order kinetic hypothesis.D-MCC with flexible surface was not suitable for the first-order kinetic.A more suitable kinetic hypothesis should be investigated in the future.

     

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