Abstract: 3-Aminopropyl triethoxy silane was used to modify the surface of iron oxide magnetic nanoparticles in this study.Glutaraldehyde was used as the cross-linking agent to immobilize alkaline protease. The results showed that the surface of modified magnetic nanoparticles had a good capability of magnetic separation so that alkaline protease was immobilized on its surface well. The best immobilization conditions for alkaline protease were alkaline protease amount of 7000 U/g, reaction temperature of 40 ℃ and reaction time of 1.5 h. The enzymatic activity after immobilization was 3352 U/g and the activity recovery was 48%. Moreover, immobilized alkaline protease retained 34.2% of the initial activity after fifth repeated use.

Key words: amino-silane, magnetic nanoparticles, immobilization, alkali protease