There has been considerable interest in the development of carrier systems used for enzyme immobilization because immobilized enzymes have enhanced stability over soluble and free enzymes which can easily be recoverable from the reaction after the assay. This leads to significant savings in terms of reduced enzyme consumption, the ability to use such enzymes in continuous processes, increased usability, reduced labour cost and to make the assay cost effective as well. The activity and stability of enzymes depends largely on the particular prevailing laboratory and storage conditions and is strongly influenced by factors such as the chemical environment, temperature, pH, and solvent preparation. Most enzymes are water soluble and an optimal volume of water is always required for their solubilization. Additionally, many enzymes require the presence of a cofactor which may be attached firmly to the enzyme or may need to be added separately as a coenzyme to enhance the chemical reaction. A significant advantage of immobilization is the increased thermal stability conferred on many enzymes by allowing their use for longer periods at higher temperatures than would be possible for the soluble molecule. An early experiment showed that immobilized papain (a protease derived from papaya latex) retained over half its room-temperature activity in conditions under which the soluble enzyme was almost entirely denatured. The interesting and valuable changes are accompanied with varied in the pH-activity curves after immobilization. A common result is found in broadening of the curve which represent the enzyme is active over a wider pH range than its soluble counterpart after the immobilization. This is normally attributed to the range of microenvironments of different enzyme molecules in or on the solid matrix. Depending on the charge properties of this matrix, the optimum pH may undergo significant shifts. The optimum pH for an enzyme bound to a negatively charged carrier such as carboxy-methyl-cellulose is shifted to higher values, while immobilization on a cationic matrix such as diethyl-amino-ethyl-cellulose (DEAE-cellulose) has the opposite effect. These effects may reflect the change in the enzyme's microenvironment brought about by neighboring charged groups. Immobilization on a neutral carrier would not be expected to change the pH optimum. Despite the advantages of enzymes immobilized on non catalytic matrices, the yield and productivity of the reaction can be reduced simply due to the presence of the non catalytic mass of the carrier. There has therefore been much interest in the development of carrier-free systems, in which enzyme molecules are linked to each other to form large complexes. These inherently immobilized the desired industrially important enzymes are no longer free to diffuse in solution, but they are largely undiluted by inert molecules and therefore retain a greater degree of activity than carrier-bound enzymes.

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.