High-density immobilization of laccase on hollow nano-sphere NH2-MIL88(Fe) host with interfacial defects to improve enzyme activity and stability for remazol brilliant blue R decolorization

Abstract

Hollow nano-sphere NH2-MIL88(Fe) (HS NMIL88(Fe)) with interfacial defects was fabricated to load laccase as a host. Through metal multi-coordination, dopamine engineered large amount of defective pores with large size on NH2-MIL88(Fe) interface. This defect-interfacial structure provided a high-density host for laccases, which efficiently protected enzyme from structure deformation and then inhibited inactivation. Besides, the unique hollow structure will help to fasten reactant diffusivity, and thus improved the catalytic reaction process. Experimental results showed that the maximum immobilized capacity and maximum activity recovery for laccase reached up to 213.2 mg/g and 75.8% beyond many state-of-the-art enzyme hosts, respectively. Meanwhile, the immobilized laccase exhibited better pH, thermal and storage stabilities on HS NMIL88(Fe) than free and loaded on NMIL88(Fe) ones. Thermal deactivation kinetics analysis showed that HS NMIL88(Fe)-Lac had much higher apparent activation energies of (105.2 kJ/mol) than that of free laccase (89.2 kJ/mol). Catalyzing decolorization performance of dye Remazol Brilliant Blue R (RBBR) was finally carried out and exhibited the decolorization rate of 1.8 times and 2.6 times faster than solid NMIL88(Fe)-Lac and free laccase, respectively. Moreover, the interaction mechanism of laccase for RBBR was investigated and revealed by molecular docking.