CROSS LINKING for ENZYME IMMOBILIZATION

Enzymes can be immobilized through cross linking using various bi- or multi- functional reagents.
The most widely used methods uses Glutaraldehyde to introduce cross links between the amino groups of the enzyme molecules.
Glutaraldehyde is a bifunctional reagent and hence cross linked and enzyme molecules. Multifunctional reagents can cross link many enzyme molecules togather.
Other reagents used for cross-linking include:

• Bisbiazo-benzidine.
• Cyanuric chloride.
• Hexa methyl-Di-isocyanate

Particles of cross-linked enzyme alone are gelatinous and lack mechanical strength. So they are first adsorbed onto a support/ carrier and then we cross link the enzymes.

Example:
Cross linking of Lipase
Sodium alginate solution is prepared by heating with a Bunsen burner and poured into a petriplate.
Later enzyme solution of lipase is poured onto the solidified algiante so that the enzyme gets adsorbed onto the solid.
Then glutaraldehyde solution is spread on the support containing adsorbed enzyme for cross-linking.

Advantages:

• The enzyme is strongly bound to the solid surface.
• The enzyme activity is high relative to the adsorption process.
• Substrate specificity of the enzyme can be changed.

Disadvantages:

• Preperation is difficult.
• Regeneration of enzyme is incompressible.
• General applicability is low.