Abstract: Chitosan microspheres were prepared by emulsion-crosslinking method for the immobilization of alkaline protease,and then the immobilization conditions were optimized by means of orthogonal test.Results showed that the activity and the recovery rate of the immobilized alkaline protease is up to 119 U/g and 49.6 % respectively under those conditions as follows:glutaral concentration 1%,ratio of alkaline protease to carrier 240 U/g,pH 10,and reaction time 20 h at room temperature.The heat resistance of the immobilized alkaline protease is stronger than that of free one and its half-life is 14 days at 4 ℃.

Key words: alkaline protease, chitosan, immobilization