Liu Wei, Zhou Fang, Zhang Xiao-Yun, Li Yue, Wang Xiang-Yu, Xu Xi-Ming, Zhang Ye-Wang
J Nanosci Nanotechnol. 2014 Apr;14(4):3068-72. doi: 10.1166/jnn.2014.8567.
Magnetic Fe3O4 nanoparticles were prepared with coprecipitatation method and covered with SiO2 to form the core-shell Fe3O4@SiO2 nanoparticles. Then the nanoparticles were modified with glutaradehyde for functionalization of the surface to aldehyde groups. The transmission electron microscopy confirmed the core-shell structure and revealed that the size of the nanoparticles was around 10 nm. It was observed that the lipase was immobilized on the nanoparticles successfully from the Fourier transform infrared spectra. The immobilized lipase on Fe3O4@SiO2 nanoparticles was characterized and compared to free enzyme. There are no significant differences observed in the optimal pH, temperature and Km before and after immobilization. However, the immobilized lipase displayed higher relative activity in the range of pH from 7.0 to 9.5. Compare with the free enzyme, the immobilized one showed higher thermal stability at temperature range from 30 to 70 degrees C, especially at high temperature. The relative activity of immobilized enzyme was 5.8 fold of the free lipase at 70 degrees C after 10 h incubation. Thus, the prepared lipase was proved to have the advantages like higher relative activity, better stability, broader pH range and easy to recovery. These results suggest that immobilization of lipase on Fe3O4@SiO2 nanoparticles has the potential industrial applications.
采用共沉淀法制备磁性Fe3O4纳米颗粒，并包覆SiO2形成核壳结构的Fe3O4@SiO2纳米颗粒。然后用戊二醛对纳米颗粒进行修饰，使表面官能化为醛基。透射电子显微镜证实了核壳结构，并显示纳米颗粒的尺寸约为10 nm。从傅里叶变换红外光谱观察到脂肪酶成功固定在纳米颗粒上。对固定在Fe3O4@SiO2纳米颗粒上的脂肪酶进行了表征，并与游离酶进行了比较。固定前后在最佳pH、温度和Km方面未观察到显著差异。然而，固定化脂肪酶在pH值为7.0至9.5的范围内表现出较高的相对活性。与游离酶相比，固定化酶在30至70摄氏度的温度范围内表现出更高的热稳定性，尤其是在高温下。孵育10小时后，固定化酶在70摄氏度下的相对活性是游离脂肪酶的5.8倍。因此，所制备的脂肪酶被证明具有相对活性高、稳定性好、pH范围宽和易于回收等优点。这些结果表明，脂肪酶固定在Fe3O4@SiO2纳米颗粒上具有潜在的工业应用价值。
