Enzyme storage stability

In general, enzymes have a disadvantage in that they are deactivated due to heat-induced structural changes or, in the case of proteolytic enzymes, due to decomposition by themselves. It is therefore desirable to distribute and use enzyme preparations in the form of solids, such as powders and granules, instead of liquids. Although drying itself is a valuable tool in the improvement of the enzyme storage stability, the process step itself often causes a substantial loss of activity and the final product is still susceptible to inactivation. 

Colloids Ltd.) that allowed an excellent enzyme storage stability after hard spray-drying conditions of LDH type XI (ex rabbit muscle) (Table 48.7). 

A critical factor for biotechnology application is the stability of the enzyme electrode. Hydrogenase immobilized into carbon filament material has high level of both operational and storage stability. Even after the half year of storage with periodical testing, the enzyme electrode preserved more than 50 % of its initial activity [9,10], Thus, it is possible to achieve appropriate stability of the enzyme electrode, suitable for hydrogen fuel cells development. 

Enzymes are biological catalysts in the form of globular proteins, and in liquid detergent compositions enzymes have inherent stability problems since the proteases not only digest the protein stains, but also the other enzymes. If this destructive mechanism is not controlled, the enzymes in the liquid detergent composition will have unacceptably short storage stability. 

In order to improve the usability of enzymes, immobilization matrices have been proposed with both environmental decontamination as well as personal detoxification in mind. Effective immobilization methods allow for the preparation of an immobilized enzyme that retains most of its native activity, maintains high operational stability as well as high storage stability. Recent advances in material synthesis using enzymes have allowed the preparation of a variety of bioplastics and enzyme-polymer composites, which involve the incorporation of the enzyme material directly into the polymer. Enzymes stabilized in this way maintain considerable stability under normally denaturing conditions [21]. A number of methods have been used to prepare bioplastic or enzyme-polymer composite materials with OP-degrading enzymes. Drevon Russel described the incorporation... 

Proteases have received less attention than lipases, but in one of the earliest papers on biocatalysis in ionic liquids it was noted that the activity loss of thermo-lysin during preincubation proceeded much more slowly in [BMIm][PF6] than in ethyl acetate [8]. The storage stability of a-chymotrypsin in the ionic liquid [EMIm][ Tf2N] was compared with that in water, 3 M sorbitol, and 1-propanol. The residual hydrolytic activity (after dilution with aqueous buffer) was measured vs time, and structural changes were monitored by fluorescence and CD spectroscopy as well as DSC [98]. The enzyme s life-time in [EMIm][ Tf2N] at 30°C was more than twice that in 3 M sorbitol, six times as long as that in water, and 96 times as long as that in 1-propanol. 

A study on tire storage stability of penicillin G in milk showed that about 60% could be destroyed within 48 h at 2 C, while 75% could be destroyed at 22 C (22). The loss of penicillin G was attributed to the hydrolytic activity of tlie enzyme -lactamase produced by both gram-negative and gram-positive bacteria of the raw milk. This was confirmed by analogous experimentation with UHT milk, in which penicillin G did not show any decrease under mentioned storage conditions. 

Enzyme and immobilisation technique Reference Mediator Assay Time (s) Lower linear range (pM) Upper linear range (mM) Applied potential (mV) Storage stability (weeks)... 

As in all catalytic processes, catalyst stability is an essential feature. We have investigated the stability of acylase in conditions that are pertinent for large-scale processes. Instead of just determining thermal stability, which can be done by measuring storage stability of the enzyme in particular conditions of temperature and pH, we have also determined operational stability. The relevant parameter for operational stability studies of enzymes is the product of active enzyme concentration [E] and residence time t, [E] t. For a CSTR, the quantities [E] and t are linked by Eq. (19.37), where [S0] = initial substrate concentration, % = degree of conversion, and r(x) = reaction rate (Wandrey, 1977 Bommarius, 1992b). 

Biosensors are obviously of use in this field due to their high selectivity, however, the problems of storage stability (biological species such as enzymes can rapidly lose their activity) and possible poisoning effects from species such as heavy metals (that may be present in real samples) need to be addressed. 

The choice of reactor configuration depends on the properties of the reaction system. For example, bioconversions for which the homogeneous catalyst distribution is particularly important are optimally performed in a reactor with the biocatalyst compartmentalized by the membrane in the reaction vessel. The membrane is used to retain large components, such as the enzyme and the substrate while allowing small molecules (e.g., the reaction product) to pass through. For more labile molecules, immobilization may increase the thermal, pH and storage stability of biocatalysts. 

Enzymes are not stable during storage in solution and their activities decrease gradually over time (21). Immobilization technique, on the other hand, is applied considering lifetime, durability, and storage stability as important parameters. It puts the enzyme into a more stable position in comparison to free enzyme. The Dowex/invertase complexes kept at 4°C in deionized water were evaluated. Table 4 shows that after 21 d, the immobilized complexes maintained 100% of AI and retained their initial activity. These results are in accordance with the storage stability of immobilized pectinase on anionic polystyrene beads, which was stable and retained its initial activity for at least 7 wk of storage at 4°C (22). 

Acetylcholineesterase and choline oxidase Enzyme membrane in H20 was treated with 11% solution of PVA-SbQ (polyvinyl alcohol) with styryl pyridinium groups. Mixture was spread on a cellulose nitrate membrane and air dried. The membrane was exposed to UV radiation for 3 h and stored at 4°C. The enzyme membrane was fixed with a Pt electrode. Sample was dissolved in phosphate buffer and measured. The best results were obtained at pH 8 and at 30°. The calibration graph was rectilinear for 5mM ACh. The storage stability of the dry membrane was excellent. [77]... 

Enzymes Enzymes immobilized in a polymer solution. Acetylcholine and choline are determined at the pM level with a precision of 3.5-7%. Detection limits were 0.1 and 1 pM of Ch and ACh, respectively. Calibration graphs were rectilinear for 0.1-100 and 1-100 pM of choline and acetylcholine. Storage stability of the sensing element is satisfactory. Response time was 3-10 min. [80]... 

Immobilized hemoglobin (Hb) on of pH from 4.5 to 9.3 and had a better storage stability than the free enzyme The immobilized Hb shows enhanced [17]... 

Covalent immobilization of enzymes increases their stability while lowering their activity. Also, their storage stability is notably higher. The synthesis of arginine from citrulline, ATP and argenino-succinate synthetase may involve a carbodiimide intermediate. ... 

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