Food industry, immobilized enzymes

Several kinds of enzymes have been used in many industries including food industries because enzymes catalyze the reaction at very moderate conditions and the reaction is very speciflc. Since enzymes are so useful and important, searching for a new enzyme with required characteristics such as higher heat stability, broader substrate specificity, etc. is inevitable. Altering some character of the currently used enzyme is extremely difficult. Immobilization of enzymes can sometimes stabilize enzymes but this is not applicable for all cases (7). Chemical modification of the enzyme also does not help so much to improve the enzyme character (2). There have been no appropriate methods to improve a character of the enzyme. 

In the early years of the chemical industry, use of biological agents centered on fermentation (qv) techniques for the production of food products, eg, vinegar (qv), cheeses (see Milk and milk products), beer (qv), and of simple organic compounds such as acetone (qv), ethanol (qv), and the butyl alcohols (qv). By the middle of the twentieth century, most simple organic chemicals were produced synthetically. Fermentation was used for food products and for more complex substances such as pharmaceuticals (qv) (see also Antibiotics). Moreover, supports were developed to immobilize enzymes for use in industrial processes such as the hydrolysis of starch (qv) (see Enzyme applications). 

Press, 1973. Lee, Y. Y. and G. T. Tsao, Engineering Problems of Immobilized Enzymes, ]. Food Technol, 39, 667 (1974). Messing, R. A., Immobilized Enzymes for Industrial Reactors, Academic Press, 1975. Torry, S., Enzyme Technology, Noyes DataCorp., Park Ridge, New Jersey, 1983. 

Furthermore, samples are not usually optically clear.On the other hand, electrochemical monitoring of these compounds can be done by biosensors. Many reports on enzyme sensors have been published for clinical and food analyses(1,2). The enzyme sensors consisted of the immobilized enzyme and an electrochemical device. However, enzymes are unstable and expensive. Therefore, the enzyme sensors are not suitable for industrial process and environmental control. 

Because of interesting and specific properties of the gel, curdlan has many potential uses not only in food industry but also as a film, a fiber, a support for immobilizing enzymes and a binding agent in tobacco product etc.(2). Besides these, an antitumor activity(3) has been reported. 

One of the most important recent developments in the use of enzymes for industrial food processing is the fixing of enzymes on water-insoluble inert supports. The fixed enzymes retain their activity and can be easily added to or removed from the reaction mixture. The use of immobilized enzymes permits continuous processing and greatly increased use of the enzyme. Various possible methods of immobilizing enzymes have been listed by Weetall (1975) and Hultin (1983). A schematic representation of the... 

Figure 10-22 Methods of Immobilizing Enzymes. Source From H.H. Weetall, Immobilized Enzymes and Their Application in the Food and Beverage Industry, Process Biochem., Vol. 10, pp. 3-6, 1975.

Weetall, H.H. 1975. Immobilized enzymes and their application in the food and beverage industry. Process Biochem. 10 3-6. 

In real applications (such as in food industries, which are presently the major users of technical grade enzymes), the cost of the support is often higher than that of the enzyme. If the enzyme is inactivated during use, it can be replaced if it is reversibly immobilized. In such a case, the stability of the enzyme does not limit the time period of usefulness of the support of the industrial catalyst. 

Microcrystalline chitin has been used as a thickening/gelling agent in the binding, stabilizing, and texturing of food [58]. Chitin is widely used to immobilize enzymes and whole cells enzyme immobilization has applications in the food industry, such as clarification of fruit juices and... 

Swaisgood has reviewed applications of immobilized enzymes in the food industry during the past 40 yr. He discusses not only the HFCS application, but also a variety of others, some of which are no longer employed commercially. Table 3 contains a summary of these applications. 

Table 3 Applications of immobilized enzymes in the food industry...

Advances in the understanding of structure-activity/selectivity relations for enzymes evolving from the use of x-ray, NMR, and other instrumental methods for characterization of enzyme structures should contribute to the development of improved immobilized enzyme systems for both analytical and industrial applications. Immobilized enzyme technology has enormous potential, but significant advances on several fronts are necessary prior to widespread industrial use of this technology. Katchalski-Katzir has discussed this problem in a review of past successes and failures in efforts to employ immobilized enzymes in the food, pharmaceutical, and chemicals industries. ... 

Enzymes immobilized on clays have been applied in various industrial processes including food technology [51], peptide synthesis [42, 43], pharmaceuticals [66], biosensors [39, 41, 46, 48], construction of modified electrodes [40, 52] as well as in bioremediation processes [50]. Table 2.1 presents some examples concerning the use of immobilized enzymes on clays. 

Despite the limitations, the great success of enzyme immobilization in diagnostics, pharmaceutical, food and chemical industries is undeniable12, 3. The decision whether one should use a soluble enzyme preparation or an immobilized enzyme does not have a universal solution and can be decided only on a case by case basis. Ordinarily, if the cost of an enzyme represents a significant portion of the overall cost or if isolation of the final product is complicated by the presence of the soluble protein, the cost of immobilization can be offset by the gains in productivity and improved product quality. The intent of this section is to describe, in general terms with illustrative examples, the features and considerations of these broad classes of enzyme immobilization as they impact their application to biocatalysis. Detailed experimental protocols are available in the original literature and exemplary protocols for these methods are offered in many excellent reviews and texts 14L... 

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