Covalent immobilization and characterization of penicillin G acylase on magnetic Fe2O3/Fe3O4 heterostructure nanoparticles prepared via a novel solution combustion and gel calcination process.

In this work, magnetic Fe2O3/Fe3O4 heterostructure nanoparticles were prepared via a novel solution combustion and gel calcination process. The glutaraldehyde was cross-linked on Fe2O3/Fe3O4 heterostructure nanoparticles decorated silica. The prepared samples were characterized by TEM, EDS, XRD, VSM, SEM, XPS, TGA/DSC, BET measurement, Raman spectroscopy, Zeta potential, HR-TEM and FT-IR. The penicillin G acylase (PGA) was covalently immobilized on magnetic Fe2O3/Fe3O4@SiO2-CHO nanocomposites via the Schiff's reaction. Variations in the observed activities as a function of immobilization time and PGA concentration have been discussed, when immobilization time and concentration of PGA were 18 h and 0.2 mg·mL-1, the activity of immobilized PGA presented optimal values of 77.8 U·L-1 and 66.2 U·L-1. The effects of pH and temperature on enzyme activity were also evaluated, the activity of PGA at the temperature of 45 °C with buffer pH of 8 arrived at the highest lever. After 12 cycles of repetitive uses, the immobilized PGA still retained around 67% of initial activity. The research results indicated that PGA immobilized on magnetic Fe2O3/Fe3O4@SiO2-CHO nanocomposites showed excellent thermal stability, pH stability, and reusability compared with free enzyme.