The Amino-Functionalized Graphene Oxide Nanosheet Preparation for Enzyme Covalent Immobilization

Enzyme immobilization has demonstrated effective means for extending protein stability and shelf life. However, current methods negatively affect the enzyme activity, particularly for application purposes. Herein, the amino functionalized graphene oxide (GO-NH₂) was synthesized and used to covalently immobilize lactase. FT-IR, UV-Vis, SEM, TEM and XPS were employed to confirm and characterize the immobilized lactase. At the resulting optimal temperature, the immobilization rate achieved 61% and the immobilized lactase maintained approximately 95% of catalyst activity. Compared with the free lactase, used as a control, the immobilized lactase was significantly more stable within acidic or basic environments, higher temperature conditions and had multiple recycle use characteristics. Furthermore, the immobilized lactase had a preserved 87% activity after storage at 4 °C for 30 days, while the free lactase was almost deactivated after 20 days under the same storage conditions. This work conforms that the amino-functionalized graphene oxide is a potential support material for lactase immobilization and can be extended to use with a variety of enzymes for a number of applications.