The development of nanobiocatalysis via the immobilization of cellulase on composite magnetic nanomaterial for enhanced loading capacity and catalytic activity.

In this study, graphene oxide (GO) decorated with 4arm‑PEG‑NH2 (molecular weight (MW) 5 K or 10 K) was constructed on magnetic Fe3O4, denoted as GO@Fe3O4@4arm‑PEG‑NH2. The morphology, structure and magnetic property of GO@Fe3O4@4arm‑PEG‑NH2 were characterized by Fourier transform infrared (FTIR), vibrating-sample magnetometer (VSM), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) in details. The saturation loading capacity of GO@Fe3O4@4arm‑PEG‑NH2 (MW 5 K and 1 K) carriers toward cellulase was 429 and 575 mg/g, respectively. Additionally, the immobilized cellulase had exhibited enhanced thermostability, storability and reusability than free enzyme. The two kinds of immobilized cellulose (MW 5 K and 10 K) retained 57% and 60% of its initial activity after 3 h at 70 °C, and retained 47% and 50% of its initial activity after 30 days' storage at room temperature. After eight times reuse, immobilized cellulose (MW 5 K and 10 K) retained 40% and 45% of its initial activity, respectively. In practical application, glucose generated by the saccharification with the immobilized cellulase was much higher than free enzyme (immobilized enzyme is kept at 2.04-2.83 times of the free enzyme), when the loading amount of enzyme was 2-8 mg, indicating the potential of the prepared biocatalyst.