Immobilization of enzymes may be defined as "enzymes physically localized in a certain confined region of space with retention of their catalytic activities and which can be used repeatedly and continuously modified to a water-insoluble form by suitable techniques. In addition, when an enzyme reaction using a substrate of high molecular weight is carried out in a reactor equipped with a semi-permeable ultra-filtration membrane without leakage of the enzyme from the reactor is considered a type of immobilized enzyme system. The term immobilized enzyme was firstly coined at the First Enzyme Engineering Conference in 1971. Previously, various terms had been used such as water-insoluble enzyme, trapped enzyme, fixed enzyme and matrix-supported enzyme. Immobilization of enzymes can be achieved by the ionic-binding method under mild conditions. However, the binding forces between enzyme and carrier are weak in comparison with those in the covalent-binding methods. Therefore, leakage of the enzyme from the carrier may occur after changes in the ionic strength, pH of the substrate, or product solution.
For immobilization of an enzyme, it is necessary that functional groups in the active center should not be involved in the binding reaction because the tertiary structure of enzyme protein is maintained by relatively weak binding forces, such as hydrogen, hydrophobic and ionic bonds. It is necessary to carry out the immobilization reaction under mild conditions/ optimum conditions. Immobilized enzymes have been widely used for many years in different industrial processes. Usually, immobilization of enzymes is carried out by three principle means, matrix assisted entrapment of enzyme, adsorption on a solid support, ionic or covalent binding. Entrapment is taken as the most preferable method because it prevents excessive loss of enzyme activity after immobilization, increases enzyme stability in microenvironment of matrix, protects enzyme from microbial contamination. The method of immobilization should be such that an enzyme faces as little conformational change as possible. The nature of the solid support or matrix plays an important role in retaining the actual confirmation and activity of enzyme in the processes that utilized immobilized biocatalysts. There has been considerable interest in the development of carrier systems for enzyme immobilization because immobilized enzymes have enhanced stability compared to soluble enzymes, and can easily be separated from the reaction. This leads to significant savings in terms of reduced enzyme consumption, and the ability to use such enzymes in continuous processes.

About Author / Additional Info:
*Corresponding Author:
Dr. Kirti Rani,
Assistant Professor (II),
Amity Institute of Biotechnology,
Amity University Uttar Pradesh, Noida,
Sec-125, Gautam Buddha Nagar, Noida-201303 (UP), India.
Off. Phone no: +120-4392946
Mobile no: +9990329492
Email ID: krsharma@amity.edu, kirtisharma2k@rediffmail.