Herein, a promising carrier, graphene oxide (GO) decorated with ZnO nanoparticles, denoted as GO/ZnO composite, has been designed and constructed. This carrier was characterized by X-ray powder diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy and thermogravimetry. Then, Candida rugosa lipase (CRL) was immobilized onto the GO-based materials via physical adsorption. Our results indicated that the lipase loading amount on the GO/ZnO composites was about 73.52 mg of protein per g. In the activity assay, the novel immobilized lipase GO/ZnO@CRL, exhibited particularly excellent performance in terms of thermostability and reusability. Within 30 min at 50 °C, the free lipase, GO@CRL and ZnO@CRL had respectively lost 64%, 62% and 41% of their initial activity. However, GO/ZnO@CRL still retained its activity of 63% after 180 min at 50 °C. After reuse of the GO/ZnO@CRL 14 times, 90% of the initial activity can be recovered. Meanwhile, the relative activity of GO@CRL and ZnO@CRL was 28% and 23% under uniform conditions. Hence, GO-decorated ZnO nanoparticles may possess great potential as carriers for immobilizing lipase in a wide range of applications.
Keywords: ZnO nanoparticles; enzyme activity; graphene oxide; immobilized CRL; reusability.