Enzyme immobilization refers to the process of confining enzymes to a solid support over which substrates are passed and converted to products. This technique improves the stability and reusability of enzymes. There are several types of enzyme immobilization methods, categorized based on the mechanism of attachment:

1. **Physical Adsorption:**
– Enzymes are adsorbed onto the surface of carriers by weak forces such as van der Waals forces, hydrogen bonds, or hydrophobic interactions.
– This method is simple and inexpensive but may lead to enzyme leaching during use.

2. **Covalent Bonding:**
– Enzymes are covalently attached to carriers through chemical bonds.
– This method provides strong attachment and reduces enzyme leaching but may affect enzyme activity due to changes in the enzyme’s structure.

3. **Entrapment:**
– Enzymes are trapped within a network of a polymer matrix or gel.
– Common materials used include alginate, polyacrylamide, and silica gel.
– Entrapment minimizes enzyme leaching but may restrict substrate access to the active site.

4. **Encapsulation:**
– Enzymes are enclosed within semi-permeable membranes or microcapsules.
– This method protects enzymes from the external environment and allows substrate and product diffusion.
– It is useful for sensitive enzymes but can be complex and expensive.

5. **Cross-linking:**
– Enzymes are chemically cross-linked with bifunctional reagents to form enzyme aggregates.
– This method creates stable enzyme structures but may require large amounts of reagents and can lead to loss of activity.

Each method has its advantages and limitations, and the choice of method depends on the specific application and desired properties of the immobilized enzyme

system.