Interfacial microenvironment for lipase immobilization: Regulating the heterogeneity of graphene oxide

Compared to the traditional chemical reduction method, a green and efficient strategy was successfully applied to regulate the surface heterogeneity of graphene oxide (GO). In this work, different kinds of amino acids were used to reduce and modify GO. The reduction and adsorption disparities of amino acids contributed to the difference of structural heterogeneity in terms of density, thermal tolerance and disorder of the oxygen-containing groups of GO. The modification also resulted in discrepancies in surface properties of the GO samples, such as hydrophobicity and surface charge. The functionalized GO was employed as a carrier for the immobilization of lipase from Thermomyces lanuginosus (lipase TL). The storage stability, the temperature and pH sensitivity of the immobilized biocatalysts and the free lipase TL were studied. Lipase immobilized on functionalized GO demonstrates superior enzymatic loading and relative activity compared to GO, with a maximum increase of 70% and 47%, respectively. The relative activity of lipase immobilized on functionalized GO was 19.21 times more than that of commercial immobilized lipase TLIM. Through molecular dynamics simulations we concluded that the increase in the relative activity of lipase TL is mainly related to its adsorption orientation and slight conformational change. Thus, our research offered a green and effective strategy to regulate the heterogeneity of nanomaterials for a suitable microenvironment to enhance the performance of immobilized lipase.