白姝，朱云风，孙彦，余林玲
AuthorsHTML:白姝，朱云风，孙彦，余林玲
AuthorsListE:Bai Shu，Zhu Yunfeng，Sun Yan，Yu Linling
AuthorsHTMLE:Bai Shu，Zhu Yunfeng，Sun Yan，Yu Linling
Unit:天津大学化工学院，天津 300350
Unit_EngLish:School of Chemical Engineering and Technology，Tianjin University，Tianjin 300350，China
Abstract_Chinese:设计具有高稳定性、活性、选择性的酶-载体复合物一直是固定化酶领域的研究重点．本文构建了聚乙烯亚胺(PEI)修饰的磁性纳米粒子(MNPs)，并用此作为载体(MNPs-PEI)通过静电作用吸附固定磷酸烯醇式丙酮酸羧化酶(PEPcase)，最后在该复合物(MNPs-ENZ)表面利用PEI诱导的仿生硅化作用生长二氧化硅壳层(MNPs-ENZ@SiO2)，以提高固定化酶的稳定性．利用透射电子显微镜、X 射线光电子能谱、振动样品磁强计、纳米粒度分析仪等表征方式证明了载体的成功合成、酶的顺利负载以及二氧化硅的成功包覆．结果表明，经仿生硅化后的固定化酶显著地提高了酶的稳定性，使得PEPcase在极端温度(50℃)或极端pH值(pH＝10.0)条件下孵育1h后依旧保持93%的活性，并且在8个循环后保存77%的酶活力．这说明仿生硅化的方法能够提高固定化酶的稳定性，该方法简便快速，环境友好，为固定化酶的进一步应用提供了参考．
Abstract_English:Designing enzyme-carrier complexes with high stability，activity，and selectivity has long been the focus of the field of enzyme immobilization. In this work，we prepared polyethyleneimine(PEI)-modified magnetic nanoparticles(MNPs)for the immobilization of phosphoenolpyruvate carboxylase(PEPcase)by electrostatic interac-tion，which is denoted as MNPs-ENZ. Then，to improve the stability of the immobilized enzyme，we coated the surface of the MNPs-ENZ with a silica layer by PEI-induced biomimetic silicification，which is denoted as MNPs-ENZ@SiO2. The PEI-modified nanoparticles(MNPs-PEI)and two immobilized enzymes(MNPs-ENZ and MNPs-ENZ@SiO2)were characterized by transmission electron microscopy，X-ray photoelectron spectroscopy，a vibrating sample magnetometer，and a nanometer-particle-size analyzer. The results reveal that the modification of PEI，immobilization of PEPcase，and coating of the silica layer were successful and that biomimetic silicification greatly improves the thermal stability，pH stability，and recyclability of MNPs-ENZ@SiO2. As an example，93% of the activity was maintained after incubation for 1h even at 50℃ or pH＝10.0，and 77% of activity was maintained after eight cycles. The above results indicate that MNPs-PEI can improve the stability of PEPcase and is a suitable carrier for enzyme immobilization. In addition，biomimetic silicification could further enhance the stability and dispersion of the immobilized enzyme，thereby confirming its potential for commercial application.
Keyword_Chinese:磁性纳米颗粒；聚乙烯亚胺；仿生硅化；磷酸烯醇式丙酮酸羧化酶；固定化酶
Keywords_English:magnetic nanoparticles；polyethyleneimine；biomimetic silicification；phosphoenolpyruvate carboxylase；enzyme immobilization

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