Question

Enzymes can be immobilized by?

A) Cross-linking enzyme molecules
B) Covalently attaching to a solid support
C) Entrapping them in gel
D) All of the above

Answer 1

Hint: Immobilized enzymes are the enzymes that are physically confined or localized in a different region of space with retention of their catalytic activities and which can be used repeatedly and continuously. Immobilization is beneficial because it facilitates work-up product isolation.

Complete step-by-step answer:
There are various methods of enzyme immobilization :
Reversible immobilization includes adsorption. 2) Irreversible immobilization includes covalent coupling, entrapment, and microencapsulation, cross-linking.
Crosslinking: This method involves the attachment of biocatalysts to each other by bi-or multifunctional reagents or ligands. In this way, very high molecular weight typically insoluble aggregates are formed. Cross-linking is a relatively simple process. It does not use any support matrix. So they are usually gelatinous and not particularly firm.
 Covalent coupling: covalent coupling is most used in which covalent bonds are formed between the surface amino acids of the enzyme and the matrix. Several chemical reagents and protocols are available for covalently linking an enzyme to the matrix. The most commonly used methods are diazotization, formation of the peptide bond, polyfunctional reagents, and amidation reaction.
 Entrapment in gel: Entrapment and encapsulation is based on the occlusion of an enzyme within a containing structure, but tight enough to release an enzyme while allowing penetration of a substrate. However, due to diffusion limitations, such methods are often unsuitable for the immobilization of enzymes hydrolyzing macromolecular substrates. Enzymes can be trapped in gels, fibre, and microcapsules.

Therefore the correct answer is Option D.
Note: Immobilized enzymes are used in research, industrial production, wastewater management, biomedical application, food industry, detergent industry, textile industry, and production of biodiesel. Immobilized enzymes provide easy recovery of the product, the product is free from the enzyme, so there is no cost of purification of enzyme, the enzyme can be used repeatedly, enzyme generally gets stabilized after adsorption.