Immobilization and Performance of Penicillin G Acylase on Magnetic Ni0.7Co0.3Fe2O4@SiO2-CHO Nanocomposites

Magnetic Ni 0.7 Co 0.3 Fe 2 O 4 nanoparticles that were prepared via the rapid combustion process were functionalized and modified to obtain magnetic Ni 0.7 Co 0.3 Fe 2 O 4 @SiO 2 -CHO nanocomposites, on which penicillin G acylase (PGA) was covalently immobilized. Selections of immobilization concentration and time of fixation were explored. Catalytic performance of immobilized PGA was characterized. The free PGA had greatest activity at pH 8.0 and 45oC while immobilized PGA's a ctivities peaked a t pH 7.5 and 45°C. Immobilized PGA had better thermal stability than free PGA at the range of 30-50°C for different time intervals. The activity of free PGA would be 0 and that of immobilized PGA still retained some activities at 60°C after 2 h. V max and K m of immobilized PGA were 1.55 mol/min and 0.15 mol/l, respectively. Free PGA's V max and K m separately were 0.74 mol/min and 0.028 mol/l. Immobilized PGA displayed more than 50% activity after 10 successive cycles. We concluded that immobilized PGA with magnetic Ni 0.7 Co 0.3 Fe 2 O 4 @SiO 2 -CHO nanocomposites could become a novel example for the immobilization of other amidohydrolases.