Immobilized enzymes and cells are very widely used for industrial analytical and therapeutic purposes besides there involvement in food production and exploring the knowledge of biochemistry, microbiology and other allied specialities.

Applications of Immobilized Cells in Commercial Production

Some of the important immobilized enzymes are aminoacylase, amylase, invertase, aspartase, fumarase etc... Aminoacylase is used for production of L-amino acids from D, L-acyl amino acids. Amylase is used for production of glucose form starch. Invertase is used for splitting of sucrose to fructose and glucose. Aspartase is used for production of aspartic acid from fumaric acid. Fumarase is used for synthesis of malic acid from fumaric acid.

Production of L-amino acids

L-amino acids are very important for use in food and feed supplement. The chemical methods employed for their production result in a racemic mixture of D and L-amino acids. They can be acylated to form D, L-acyl amino acid. The immobilized enzyme amino acylase frequently immobilized on DEAE-sephadex can selectively hydrolyse D, L-acyl amino acid to produce L-amino acids.

The free L-amino acids can separated from the unhydrolysed deacyl amino acids. The later can be racemized to D, L-acyl amino acid and recycled through the enzyme reactor containing immobilized amino acylase. Huge quantities of L-methionine, L-phenylalanine, L-tryptophan, and L-valine are produced worldwide by this approach.

Production of High Fructose Syrup

Fructose is the sweetest among the monosaccharides and twice the sweetening strength of sucrose. Glucose is about 75% as sweet as sucrose. Therefore glucose the most abundant monosaccharides cannot be a good substitute for sucrose for sweetening. Thus there is a great demand for fructose which is very sweet but has the same calorific value as that of glucose or sucrose.

High fructose syrup contains approximately equivalent amount of glucose and fructose. High fructose syrup is almost similar to sucrose form nutritional point of view. High fructose syrup is a good substitute for sugar, in the preparation of soft drink, processed food and baking.
High fructose syrup can be produced from glucose by employing an immobilized enzyme glucose isomerase. The starch containing raw materials like wheat, potato, corn are subjected to hydrolysis to produce glucose. Glucose isomerase then isomers glucose to fructose. The product forms are high fructose syrup. It contains about 50% fructose.

Glucose isomerase is an intracellular enzyme produced by a number of microorganisms the species of Arthrobacter, Bacillus and Streptomyces are the preferred sources. Being an intracellular enzyme the isolation of glucose isomerase without loss of biological activity requires special and costly techniques. Many a time's whole cells or partly broken cells are immobilized and used.

Production of Antibiotics

The antibiotic penicillin can be produced by using an immobilized enzyme from the culture of penicillin production cultures in fermentation. Immobilized cell and enzyme cultures can also produce other antibiotics like ampicillin, bacitracin, amoxicillin, tylosin and nikkomycin.

Production of Other Important Products

Immobilized enzymes are also used for production of several commercially important product like steroids, organic acids such as malic acid, lactic acid.

Immobilized enzymes are employed for production of Coenzyme A.

Immobilized enzymes are employed for production of anthraquinones by de-novo synthesis.

Immobilized enzymes can also be used for production of prostaglandins, proinsulins etc.

Application of Immobilized Cells in Analytics

In Biochemical Analytical Application

Immobilized enzymes or cells can be used for the development of precise and specific analytical techniques for the estimation of several biochemical compounds. The principle of analytical assay primarily involves the action of the immobilized enzymes on the substrates. A decrease in the substrates concentration or an increase in the product level or an alternation in the cofactor connections can be used for the assays.

Two types of detector systems are commonly employed.

1. Thermistors
2. Electrodes

Thermistors are heat measuring devices which can record the heat generated in an enzyme catalysed reaction. Electrode devices are used for measuring potential differences in the reaction system. These electrode sensors are used for detection of urea, cholesterol and some antibiotics. These immobilized sensors are also used for detection and quantification of serum level of lipids and lipid substances.

In Affinity Chromatography and Purification

Immobilized enzymes can be used in affinity chromatography based on the property of affinity. It is possible to purify several compounds that are antigens antibodies and cofactors.

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