Nanoarchitectonics of penicillin G acylase with Mn2+ doped β-cyclodextrin/Fe3O4 for enhanced catalytic activity and reusability

In this work, Fe3O4 nanoparticles (NPs) were synthesized by reverse microemulsion method. After that, in a strong alkaline environment, the Fe3O4 NPs were coated with β-cyclodextrin (β-CD). Then γ-glycidoxypropyltrimethoxysilane (KH560) was used to modified Fe3O4@β-CD NPs to obtain Fe3O4@β-CD-g-KH560 NPs. Through the click reaction between the epoxy group of KH560 and the amino group of Penicillin G acylase (PGA), the covalent immobilization of PGA was realized under mild conditions. The results showed that the enzyme activity (EA), enzyme activity recovery (EAR) and maximum loading (ELC) of immobilized PGA were 28242 U/g, 84 % and 112 mg/g, respectively. Its enzyme activity was kept at 43 % after repeated use for 4 times. Afterwards, in the process of β-CD coating Fe3O4 NPs, Mn2+ doped, and Scanning electron microscopy - Energy dispersive spectrometer (SEM-EDS) was used to scan the metal ion doped sample. The results showed that Mn2+-Fe3O4@β-CD-g-KH560 NPs performed higher EAR and reusability (Ra (%)) than Fe3O4@β-CD-g-KH560 NPs. The immobilized PGA performed higher EAR and reusability, i.e. its EA, EAR and ELC were 31528 U/g, 94.2 % and 105 mg/g, respectively, and 72 % of the original enzyme activity was remained after repeated use for 11 times. Furthermore, the structures of the magnetic composites were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Vibrating sample magnetometer (VSM) and Transmission electron microscopy (TEM).