Immobilized Penicillin acylase was prepared by using a novel composite support PEI/SIO2

the optimum pH and temperature of the free enzyme and immobilized enzyme were examined

and the continuous operation stability and the resistance to metal ions were studied.At the same time

Michaelis-Menten constants of the free enzyme and the immobilized enzyme were measured

respectively.The experiment results show that the optimum pHs of free enzyme and immobilized enzyme are 9.32 and 7.34.Respectively

the optimum pH of the immobilized enzyme is shifted to acidity and the range of the suitable pH is widened.The optimum temperature of the free enzyme is 50 ℃

and the catalysis activities are very low at lower or higher temperature.Whereas for the immobilized enzyme

optimum temperature is 40 ℃

the range of the suitable temperature is widened obviously

and higher activity always can be retained from 20 ℃ to 60 ℃.The immobilized enzyme has better continuous operation stability and resistance to metal ions.Michaelis-Menten constants of the immobilized enzyme and the free enzyme are 2.38×10-1 mol/L and 5.44×10-2 mol/L

respectively.