【作者】 许伟；

【导师】 张霞；

【作者基本信息】 东北大学 ， 化学工程， 2019， 硕士

【摘要】 酶固定化是提高生物酶稳定性,扩展生物酶催化技术的重要课题。金属有机骨架(MOFs)化合物具有大的比表面积、超高的孔隙率、可调的框架结构以及孔隙大小,聚偏氟乙烯(PVDF)是一种性能优异的聚合物多孔膜,具有良好的生物相容性。将MOFs与聚合物多孔膜相结合,开发新的生物酶固定载体材料在酶固定工程领域具有重要意义。本文成功制备了沸石咪唑酯骨架(ZIF-8)掺杂的聚偏氟乙烯(PVDF)杂化膜(ZIF-8/PVDF杂化膜),用于纤维素酶固定。分别采用三种不同的杂化方法,包括机械混合方法(A),氨化后的自组装(B)和配体官能化后的自组装(C)制备具有不同负载量的ZIF-8/PVDF杂化膜材料。应用场发射扫描电子显微镜(FESEM),X射线衍射(XRD),傅里叶变换红外光谱(FT-IR)和热重分析(TG)等手段研究了 ZIF-8/PVDF杂化膜的形貌、晶体结构和表面性质。通过测量表面水接触角来表征杂化膜的疏水/亲水性质。纤维素酶的固定化试验表明,与纯PVDF膜相比,ZIF-8/PVDF杂化膜对纤维素酶的平衡吸附能力均大大提高。其中,ZIF-8/PVDF(A-2)具有最佳的吸附性能,相当于PVDF原膜吸附量的1.2倍。与游离纤维素相比,固定化酶保持了较好的活性,同时显著提高了对pH值,温度和储存天数的稳定性。MIL-101(Cr)是一种基于对苯二甲酸和Cr3+的MOF材料。本文通过物理掺杂制备MIL-101(Cr)/PVDF复合膜,并用于对过氧化氢酶的吸附实验中,对于过氧化氢酶的最佳吸附条件进行优化:pH=5,吸附时间t=60min,离子强度c(NaCl)=0 mol/L及温度T=40℃,MIL-101(Cr)/PVDF杂化膜对过氧化氢酶的最大吸附量为81.13μg/cm2。吸附动力学拟合结果表明,MIL-101(Cr)/PVDF对过氧化氢酶的吸附更适合拟二级动力学结果,且等温吸附模型拟合更符合Langmuir等温模型。对固定化酶的活性测试实验表明,MIL-101(Cr)/PVDF复合膜对过氧化氢酶的固定化保持了纤维素酶的催化活性,并相对提高了过氧化氢酶对pH条件和温度的稳定性。更多还原

【Abstract】 Enzyme immobilization with its activity finely preserved has attracted tremendous attention in the fields of biochemistry,biosensor,and biomedicine.Metal-organic frameworks(MOFs)have large specific surface area,ultra-high porosity,uniformity,adjustable frame and structure,and void size of MOFs,and polyvinylidene fluoride(PVDF)is an excellent polymer porous membrane with good biocompatibility.Therefore,combining MOFs with polymer porous membranes to fabricate new solid carries used in the immobilization of enzymes with maintained the catalytic activity and stability of biological enzymes has great significance in enzyme immobilization engineering.In this thesis,zeolitic imidazolate framework(ZIF-8)incorporated polyvinylidene fluoride(PVDF)hybrid membranes(denoted as ZIF-8/PVDF hybrid membranes)were successfully fabricated for effective enzyme immobilization.Three different hybridization methods,including mechanical blending method(A),self-assembly after amination(B),and self-assembly after ligand functionalization(C),were employed to fabricate ZIF-8/PVDF hybrid membranes with various loading amounts of ZIF-8 composites.The morphologies,phases,and constituents of the ZIF-8 nanoparticle functionalized hybrid membranes were investigated by field emission scanning electron microscope(FESEM),X-ray diffraction(XRD),Fourier-transform infrared spectroscopy(FT-IR)and Thermal gravity analysis(TG),respectively.The hydrophobic/hydrophilic properties of the hybrid membranes were also investigated through measuring the surface water contact angle.The immobilization tests of cellulase demonstrated that the equilibrium adsorption capacity of cellulase on the as-prepared ZIF-8/PVDF hybrid membranes is greatly improved in comparison to that of the pure pristine PVDF membrane.In addition,the adsorption capacity of cellulase on ZIF-8/PVDF is correlated with the synthetic method and the loading amount of ZIF-8 nanocrystals.Among them,the ZIF-8/PVDF(A-2)presented the best adsorption activity,which was almost 1.2 times as that of the property on pristine PVDF.Compared to free cellulose,the immobilized enzyme kept activity and meanwhile significantly improved the stability against pH values,temperature and storage days.MIL-101 is a chromium terephthalate-based mesoporous MOFs,which is also applied in the fabrication of MIL-101(Cr)/PVDF hybrid membranes through a physical belnding method,wich is then used in the adsorption of catalase.The adsorption conditions were optimized,and the maximum adsorption capacity was 81.13μg/cm2.The adsorption kinetics fitting results showed that the adsorption of catalase by MIL-101(Cr)/PVDF is more suitable for pseudo-second-order kinetics,and the isothermal adsorption model is more applicable with the Langmuir isotherm model.The activity tests of immobilized enzyme showed that the immobilized catalase maintained its catalytic activity,and meanwhile increases the stability of the catalase against the pH condition and elevated temperature.更多还原