4. Conclusion

MOFs, with extremely high specific surface area, abundant porosity and extraordinary multi-functionality, hold a great promise as matrices for enzyme immobilization with biocompatibility and high protein loading capacity and enhance the cost-efficiency of biocatalysis. The D-amino acid dehydrogenase connected with (RTHRK)4 was constructed. Combined with peptide linker and MOF, efficient enzyme immobilization was achieved by encapsulation of DAADH via a facile one-step biomimetic mineralization strategy. These results indicated the interactions of MOF and peptide linker substantially improved the catalytic efficiency and stability of DAADH. After 10 hours of incubation at 50 °C, DAADH/ZIF-8/RGO retained 53.4% relative activity while that is 37.8% for DAADH/ZIF-8, and the free enzyme was almost inactivated. After 7 recycles, the residual activities of DAADH/ZIF-8/RGO and DAADH/ZIF-8 were 64.3% and 45.6%, respectively. Furthermore, one-step separation and immobilization by DAADH-ZIF-8/RGO/Ni-DAADH was carried out with 1.5-fold activity enhancement. Hybrid materials of MOF and carbon materials also can be extended for the multi-enzyme immobilization, which have potential in biocatalysis.