Abstract: Fe3O4 magnetic nanoparticle was prepared by chemical co-precipitation method，and magnetic chitosan microsphere was prepared through crosslink emulsification process applying Fe3O4 magnetic nanoparticle as magnetic nuclear. Also，the properties of magnetic composite microsphere were characterized. Crude angiotensin converting enzyme(ACE) extracted from hog lungs was immobilized on magnetic chitosan microspheres，factors influencing the immobilization were investigated. The experimental results showed that the optimal conditions for preparation immobilized ACE were immobilization pH=8.3，temperature 50 ℃，time 1.5 h and protein concentration of ACE 6 mg/mL，with a optimal specific activity of 0.048 U/g spheres. Compared with free ACE，pH and thermal stability of immobilized ACE were increased. After 10 repetitive operations，the activity of immobilized ACE remained more than 40% of its initial activity. These results indicated that magnetic chitosan microsphere can be a kind of good support for immobilizing ACE.

Key words: magnetic, chitosan microspheres, immobilization, angiotensin converting enzyme

摘要： 以化学共沉淀法合成Fe3O4纳米粒子为磁核，采用乳化交联法制备磁性壳聚糖微球，并对其形貌、结构和磁饱和强度等性质进行了表征。以磁性壳聚糖微球作为载体，固定化猪肺粗提物中的血管紧张素转化酶，并对固定化条件进行研究。结果表明，固定化血管紧张素转化酶的最佳条件为：pH值为8.3，最佳温度为50 ℃，最佳时间为1.5 h，最佳酶溶液蛋白浓度为6 mg/mL，此时固定化酶活力最高为0.048 U/g微球。与游离酶相比，固定化酶的pH值稳定性和热稳定性均得到提高。固定化酶重复使用10次，仍然保持40%以上相对活力，说明磁性壳聚糖微球是固定化血管紧张素转化酶的良好载体。

关键词: 磁性, 壳聚糖微球, 固定化, 血管紧张素转化酶