How Do You Immobilize an Enzyme?
Enzymes and cells have been immobilized on substances ranging from paper, wood chips, and crushed red brick through conventional ion exchange resins to sophisticated and costly ceramic and glass beads. But in general, says Alexander Klibanov of the Massachusetts Institute of Technology, immobilization techniques can be divided into five major classes.
Adsorption on solid supports. The most popular supports are ion-exchange resins, but many other materials can be used. This is the simplest and cheapest approach: an enzyme solution is added to the support, the system is stirred, and the unattached enzyme is washed away. The adsorbed product is not very stable, however, and cells are more easily adsorbed than enzymes.
Covalent attachment to supports. Many different supports can be used, but the most popular are porous ceramics such as those developed by Corning Glass Works. A major problem is the potential for inactivation of the active site by chemical reagents, but this can often be avoided by binding a substrate or ligand to the active site during the immobilization process. This technique is...