Immobilised enzymes

To maximise efficiency many enzymes are immobilised. Immobilised enzymes are trapped within or attached to appropriate inorganic or organic materials.

Four principal methods of immobilisation:

• adsorption - enzyme is attached by weak forces to the outside of an inert material such as glass or matrix
• entrapment - enzymes are trapped within polymers (a gel) such as alginate beads or microspheres
• encapsulation - enzymes are trapped inside a selectively permeable membrane such as nylon
• cross-linkage - enzymes are bonded covalently to a matrix, such as cellulose, as a consequence of chemical reactions (or even to each other using linking chemicals)

The gels or materials involved in some types of immobilisation may reduce the speed of diffusion between substrate and enzyme. The immobilisation process may also hold some enzymes in physical positions that make some of the enzyme active sites inaccessible.

Immobilisation provides advantages in the commerical use of enzymes:

• the product is…