Enzyme industrial inactivation

Ultra-high-temperature treatment (UHT) is now the most widely exploited method in the food industry to stabilize microbiologically any foodstuff. It consists of heating at an ultra high-temperature for a short period of time for example, a treatment at 145°C for 2 seconds is sufficient to assure a total microbial- and spore inactivation. The microbial death is principally due to irreversible cell damage (e.g., of proteins, DNA, RNA, vitamins) enzymes are inactivated by heat which modifies their active sites. 

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. 

Some of these differences can be attributed to variations in detoxication mechanisms. For example, the loss of consciousness induced in several species of laboratory animals by hexobarbital (a barbiturate derivative that depresses the central nervous system (CNS)) shows marked differences these are attributable to the activity of the detoxication enzyme that inactivates this chemical. In the mouse, the activity of the detoxifying enzyme is 16-fold greater than that in the dog, which is reflected by 12 min of hexobarbital-induced sleep in the mouse versus 315 min of sleep in the dog. There are other examples of species-related differences in the ability to detoxify chemicals that consequently result in differences in toxicity. Other examples include the industrial chemicals, ethylene glycol and aniline. Ethylene glycol is metabolized to oxalic acid, which is responsible for its toxicity, or to carbon dioxide. The rank order of ethylene glycol toxicity in animals is as follows cat rat rabbit this is the same for the extent of oxalic acid production. Aniline is metabolized in the cat and dog mainly to o-aminophenol, and these species are more prone to toxicity however, in the rat and hamster aniline is metabolized mainly to I-aminophenol and thus these species are less susceptible to aniline toxicity. 

As described above, the polyacrylamide gel method is advantageous for Immobilization of microbial cells and for industrial application. However, there are some limitations in this method. That is, some enzymes are inactivated during Immobilization procedure by the action of acrylamide monomer, 8-dimethylamino-propionitril, potassium persulfate or heat of the polymerization reaction. Therefore, this method has limitation in application for immobilization of enzymes and microbial cells. Thus, to find out more general Immobilization technique and to Improve the productivities of Immobilized microbial cell systems we studied new immobilization techniques. As the results, we have found out K-carrageenan is very useful for Immobilization of cells [8]. <-Carrageenan, which is composed of unit structure of B-D-galactose... 

Enzymes not only produce characteristic and desirable flavor (79) but also cause flavor deterioration (80,81) (see Enzyme Applications, Industrial). The latter enzyme types must be inactivated in order to stabilize and preserve a food. Freezing depresses enzymatic action. A more complete elimination of enzymatic action is accompHshed by pasteurization. 

Enzyme—Heat—Enzyme Process. The enzyme—heat—enzyme (EHE) process was the first industrial enzymatic Hquefaction procedure developed and utilizes a B. subtilis, also referred to as B. amjloliquefaciens, a-amylase for hydrolysis. The enzyme can be used at temperatures up to about 90°C before a significant loss in activity occurs. After an initial hydrolysis step a high temperature heat treatment step is needed to solubilize residual starch present as a fatty acid/amylose complex. The heat treatment inactivates the a-amylase, thus a second addition of enzyme is required to complete the reaction. 

DEVECE C, RODRIGUEZ LOPEZ J N, FENOLL L G, TUDELA J, CATALA J M, DE LOS REYES E and GARCIA CANOVAS F (1999) Enzyme inactivation analysis for industrial blanching applications comparison of microwave, conventional, and combination heat treatments on mushroom polyphenoloxidase activity , J g-nc Food Chem, 47 (11) 4506-11. 

Used industrially as a chemical intermediate in the manufacture of couplers for color photography, as a photo polymerization agent for vinyl compounds, as a solvent, and as an enzyme inactivator in biological research. 

Sometimes CYPs can also produce reactive metabolite species that, instead of undergoing the normal detoxification pathway, can act as irreversible CYP inhibitors, thus causing toxicity. Such reactive metabolites that cause CYP inactivation are called MBI and are described in Chapter 9. Mechanism-based enzyme inhibition is associated with irreversible or quasi-irreversible loss of enzyme function, requiring synthesis of new enzymes before activity is restored. The consequences of MBI could be auto-inhibition of the clearance of the inactivator itself or prolonged inhibition of the clearance of other drugs that are cleared by the same isozyme. There may also be serious immunotoxicological consequences if a reactive intermediate is covalently bound to the enzyme. Therefore, screening of new compounds for MBI is now a standard practice within the pharmaceutical industry. 

Proteases are the most extensively used enzymes in the food industry, where they act to improve the quality, stability, and solubility of foods. Some of the attributes of enzymes which make them useful in industrial operations include the following 1) They are derived from plants, animal, and microbial sources and are invariably nontoxic substances that are able catalyze specific reactions 2) they are active at very low concentrations under mild conditions of temperature and pH where undesirable side reactions are minimized and 3) they can be inactivated after a desired effect has been achieved. Proteases from plant, animal, and microbial sources find extensive use as food processing aids.(32) Some of the applications of proteases in the food industry are summarized in Table I. 

Penicillin amidase is used industrially to produce 6-aminopenicillanic acid (6-APA) from penicillin G or V (see section 4.5). Acid is produced during the process and this will inactivate the enzyme. One way of overcoming this problem is by using a fixed bed reactor with immobilized enzyme. The substrate is pumped very rapidly... 

To overcome problems of poor acceptor substrate acceptance, high concentrations of aldehyde substrates are required to obtain synthetically useful product yields. Unfortunately, DERA shows rather poor resistance to such high aldehyde concentrations, especially toward CIAA, resulting in rapid, irreversible inactivation of the enzyme. Therefore, the organic synthesis of (3R,5S)-6-chloro-2,4,6-trideoxy-hexapyranoside 1 requires very high amounts of DERA. Thus, despite the synthetic usefulness of DERA to produce chiral intermediates for statin side chains, the large-scale application is seriously hampered by its poor stability at industrially relevant aldehyde concentrations. The production capacity for such 2,4,6-trideoxy-hexoses of wild-type E. coli DERA is rather low [15]. 

Erom the results presented in Figure 6.4 it is clear that the loss of enzyme activity over time is dramatic when either ClAA or AA concentrations exceed 100 mM, resulting in half-life times in the range of 5-7 h at industrially relevant concentrahons. The first aldol condensation product also rapidly inactivates DERA at concentrahons above 100 mM. Although the final product 1 seems to have a less pronounced effect on the stability of the enzymes. Figure 6.4 indicates that the achvity in the presence of the compound is low. 

The purpose of pasteurization, as it is practiced in the domestic industry today, is to destroy spoilage organisms, inactivate enzymes, or both. Heating to temperatures of only 150°F (65.6°C) will destroy most spoilage organisms but some heat resistant molds may require pasteurization temperatures as high as 210°F (98.9°C) for control. 

Unstabilized bran and polish have been used almost exclusively for animal feed, due to the bitter flavor that develops from the lipolytic action of enzymes on the oil found in them. However, development of a thermal process that inactivates the lipases has resulted in a stabilized rice bran product that is suitable for the food industry. The impressive nutritional qualities of the oil, fiber, carbohydrate and proteins of rice bran have made it a valuable food material. Removal of fiber from the bran by physical K,J7or enzymic1819 processes produces a milk-like product having desirable nutritional and functional properties. The nutritional composition of the rice bran milk product described by California Natural Products has been shown to match the nutritional requirements of an infant formula. Originally, the anti-nutritional factor of the residual phytates was of concern. However, as of 2005, phytase enzymes are suitable for use to break down these phytates. 

Chemical modification has the drawback that the modified protein often shows a much reduced activity with respect to the native enzyme, and the effect on enzyme selectivity is unpredictable. A further weak point in using biocatalysts is that they are much more expensive with respect to conventional catalysts and, in order to be economically convenient from an industrial point of view, they must show a large number of turnover cycles before degradation. If the enzyme has very high activity and/or it is not excessively precious, its recycle from the product mixture may not be necessary. Otherwise, the protein must also be easily separated from the reaction mixture, without undergoing inactivation. 

Another limitation in the industrial application of peroxidases is the low stability to H202 (see Chap. 12). Here, an improvement for H202 inactivation through the physical immobilization of CPO on the mesoporous sieve SBA-15 of 130 A for the oxidation of indole to 2-oxoindole has been reported [8]. The performance of the immobilized enzyme was enhanced to that of the native CPO with respect to maximum conversion. According to the authors, the superior performance of... 

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