Enzyme Immobilization

Enzyme Immobilization

Microbial enzymes are most extensively employed in the food and beverage industries across the globe to meet the ever increasing demand for nutritionally superb and high-value products. In actual practice, the soluble enzymes engaged in ‘batch operations’ is found to be not-so-economical due to the fact that the active enzyme is virtually lost (not recovered) after each viable reaction. Therefore to overcome this problem we are immobilized enzymes after reaction & reuse them.

Immobilized enzymes have been defined as enzymes that are physically confined or localized, with retention of their catalytic activity, and which can be used repeatedly and continuously and the process is called enzymes immobilization.

There is a variety of methods by which enzymes can be localized, ranging from covalent chemical bonding to physical entrapment however they can be broadly classified as follows:

1. Covalent bonding of the enzyme to a derivatized, water-insoluble matrix.

2. Intermolecular cross-linking of enzyme molecules using multi-functional reagents.

3. Adsorption of the enzyme onto a water-insoluble matrix.

4. Entrapment of the enzyme inside a water-insoluble polymer lattice or semi-permeable membrane

Advantages of Enzyme Immobilization

(1) Enzymes being quite expensive and also having the unique ability to be used repeatedly only in a situation when these may be recovered completely from the accomplished reaction mixtures. In true sense, immobilization distinctly and specifically allows their repeated usage by virtue of the fact that such enzyme preparation may be separated conveniently from the reaction system involved.

(2)     Importantly, the final desired product should be readily from the enzyme. It goes a long way in affecting reduction and saving upon the cost of ‘downstream processing’ of the ensuing end-product.

(3)     Non-aqueous systems (i.e., using organic solvents exclusively) are found to be fairly compatible with the immobilized enzymes particularly, and this may be regarded to be extremely desirable in certain typical and specific instances.

(4)     Immobilized enzymes may be used predominantly in most continuous production systems; and, of course, this not absolutely feasible and possible with the ‘free-enzymes’.

(5)     Immobilized enzymes, a few selected ones, may exhibit thermo stability of the highest order, viz., the free-enzyme glucose isomerase usually gets denatured only at 45°C in solution ; however, when immobilized suitably the enzyme is found to be stable enough up to 1 year at 65°C.

(6)     Importantly, the ultimate recovery of ‘immobilized enzyme’ would drastically minimize the high effluent disposable problems (which is quite acute in several fermentation industries).

(7) Immobilized enzymes may be employed at a much higher concentration range in comparison to the corresponding free enzyme.

Disadvantages of Enzyme Immobilization

Immobilized enzymes do offer several disadvantages which are briefly discussed in the section that follows:

(1) Enzyme immobilization evidently gives rise to an additional bearing on cost. Hence, this improved technique is got to be used only in such an event when there prevails a sound economic viability, feasibility, safety, and above all a positive edge over the corresponding ‘soluble enzymes’.

(2)             Immobilization of enzymes invariably affects the stability and or activity adversely. In order to circumvent such typical instances one may have to adhere strictly to the laid down developed immobilization protocols

(3)            Practical utilization of the ‘immobilized enzymes’ may not prove to be of any use or advantage when one of the substrates is found to be insoluble.

(4)             Certain immobilization protocols do offer a good number of serious problems with respect to the diffusion of the ensuing substrate to have an access to the corresponding enzyme.