Magnetic mesoporous microspheres modified with hyperbranched amine for the immobilization of penicillin G acylase

Fe₃O₄@SiO₂@m-SiO₂ magnetic mesoporous (SmSMM) microspheres were synthesized by two steps Stöber hydrolysis. The surface of the SmSMM microspheres were modified with γ-(2,3-epoxypropoxy)propytrimethoxysilane (KH560) and dendritic hyperbranched amine (DHA) to obtain SmSMM-DHA microspheres, which were used as carriers for the immobilization of penicillin G acylase (PGA). The diameter of SmSMM-DHA microspheres was around 500 nm and the specific saturation magnetization was 61.25 emu g⁻¹. The advantages of the as-prepared carries were large specific surface area and high amino content, the values were 323.1 m² g⁻¹ and 2.1 mmol g⁻¹, respectively. The influences of the factors on amino content, immobilization rate and enzyme activity were investigated. The research results of PGA immobilized on SmSMM-DHA microspheres indicated that compared with free enzyme, the immobilized PGA showed excellent pH and thermo stability. Meanwhile, after being used for ten times, the enzyme activity retention rate was 94.5%. The designed immobilized enzyme shows potential application value in the synthesis of antibiotics.