Immobilized enzymes, advantages

Immobilized Enzymes. The immobilized enzyme electrode is the most common immobilized biopolymer sensor, consisting of a thin layer of enzyme immobilized on the surface of an electrochemical sensor as shown in Figure 6. The enzyme catalyzes a reaction that converts the target substrate into a product that is detected electrochemicaHy. The advantages of immobilized enzyme electrodes include minimal pretreatment of the sample matrix, small sample volume, and the recovery of the enzyme for repeated use (49). Several reviews and books have been pubHshed on immobilized enzyme electrodes (50—52). 

A significant advantage of immobilized enzymes is the total absence of catalytic activity in the product. Moreover, the degree of substrate-to-product conversion can be controlled during processing, eg, by adjusting the flow rate through a packed-bed column reactor of immobilized enzyme. 

Solutions of surfactant-stabilized nanogels share both the advantage of gels (drastic reduction of molecular diffusion and of internal dynamics of solubilizates entrapped in the micellar aggregates) and of nonviscous liquids (nanogel-containing reversed micelles diffuse and are dispersed in a macroscopicaUy nonviscous medium). Effects on the lifetime of excited species and on the catalytic activity and stability of immobilized enzymes can be expected. 

Addition of third components to nanohybrids of proteins and mesoporous materials sometimes brings advantages in their functions. Kim, Hyeon, and coworkers immobilized enzyme molecules together with magnetite (Fe304) nanoparticles in hierarchically ordered, mesocellular, mesoporous silica (HMMS) (Figure 4.25)... 

Membrane-Enclosed Enzymatic Catalysis (MEEC) has been developed as a useful, practical new method for the manipulation of enzymes in organic synthesis. The enzyme in soluble form is enclosed in commercially available dialysis membranes. It combines the simplicity of use of soluble enzymes with certain of the advantages of immobilized enzymes. Containment permits separation of the enzyme from the reaction medium, straightforward separation of the product, and recovery of the enzyme for reuse [53],... 

A further advantage, as described by Thomas et al. [19], is the possibility of protein identification that follows the functional characterization of the enzyme. The activity of an enzyme is initially determined by following the substrate consumption and product formation in the first assay (Fig. 8.10). Since no matrix components are present in the sample spot, the immobilized enzyme is then directly... 

In summary, the synthesis and in situ regeneration of nucleotide sugars by combinatorial biocatalysis suffers from the main disadvantage that each enzyme has to be produced in sufficient amounts. This affords efficient recombinant protein produchon hosts being a bottleneck for some genes [25]. However, once a multi-enzyme system has been developed, the productivity can be improved by repetitive use of the biocatalysts as demonstrated for repetitive batch syntheses with soluble enzymes [25, 38] or with immobilized enzymes [48]. The advantage... 

Immobilized enzymes and cells, which are now known as immobilized biocatalysts, both provide us in general with the following advantages (1) continuous operation becomes practical (2) biocatalysts can be recovered and reused after reactions (3) biocatalysts can be formed into the shapes, such as membranes or beads, required for specific reaction processes (4) in some cases, the biocatalysts become stable with regard to changes in temperature, pH and inhibitor concentration. Immobilization methods can be classified according to the following scheme,... 

A renewed interest in this research field may lead to the construction of functional immobilized biocatalysts that surpass the conventional definition, or usually credited advantages, of immobilized biocatalysts with regard to their capabilities as catalysts [22-24], i.e. immobilized enzyme systems in which, for example, an enzymatic process can be controlled by externally applied stimuli such as light, electric fields, pH, temperature, and mechanical force. In such cases, what is crucial in system construction is not to rely on a possible... 

Immobilized Enzymes in Diagnostic Reagents. The use of immobilized. instead of soluble, enzymes for measurement of analytes lias received considerable attemion. especially lor clinical analyses. Use of immobilized enzymes offers the advantages of greater accuracy, stability, and convenience. Only a few meihods utilizing immobilized enzymes have become commercially available. 

Polarimetry takes advantage of the optical activity of carbohydrates. The high selectivity of this procedure makes it especially suitable in the case of complex food extracts, where other components would interfere with ultraviolet or refractive index detection. However, a major disadvantage is its lower sensitivity. The use of immobilized enzymes (51) with detection by fluorescence or electrochemistry has also been applied in fermentation juices (52) and other particular cases. 

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