Carriers, enzyme immobilization

Porous glass (PG) modified with covalently adsorbed poly(p-nitrophenyl acrylate), as described in Sect. 4.1, turned out to be a highly suitable carrier for immobilization of various biospecific ligands and enzymes. When the residual active ester groups of the carrier were blocked by ethanolamine, the immobilized ligands when bound to the solid support via hydrophilic and flexible poly(2-hydroxyethyl acrylamide). The effective biospecific binding provided by the ligands... 

Rasor and Tischer (1998) have brought out the advantages of enzyme immobilization. Examples of penicillin-G to 6-APA, hydrolysis of cephalospwrin C into 7-ACA, hydrolysis of isosorbide diacetate and hydrolysis of 5-(4-hydroxy phenyl) hydantom are cited. De Vroom (1998) has reported covalent attachment of penicillin acylase (EC 3.51.11) from E.Coli in a gelatine-based carrier to give a water insoluble catalyst assemblase which can be recycled many times, and is suitable for the production of semi-synthetic antibiotics in an aqueous environment. The enzyme can be applied both in a hydrolytic fashion and a synthetic fashion. 6-APA was produced from penicillin-G similarly, 7-ADCA was produced from desa acetoxycephalosporin G, a ring expansion product of penicillin G. 

Cao, F. (2005) Carrier-Bound Immobilized Enzymes, Principles, Applications and Design, Wiley-VCH, Weinheim. 

Adsorption on solid matrices represents a quite simple and inexpensive method for enzyme immobilization. Enzyme dispersion is improved, reducing the diffusion limitations and favoring the accessibility of substrate to the enzyme [12]. On the other hand, because of the weak binding, the system can suffer from catalyst leaching, and there is little stabilization of the enzyme. The most common carriers... 

Relatively little attention has been paid to enzyme immobilization in connection with ionic liquids, and only one systematic study of this subject has appeared [78]. Itoh et al. studied the effects of the carrier material on PcL in [BMIm][PF6] [79]. The activity of PsL on ceramic Toyonite carriers varied by a factor of 1000 between Toyonite 200M and Toyonite 200A. PsL adsorbed on a methacryloxypropyl-modified mesoporous silica also had a relatively high activity [78]. 

W. II. Pitcher Design and Operation of Immobilized Enzyme Reactors. - S. A Barker Biotechnology of Immobilized Multienzyme Systems. - R. A Messing Carriers for Immobilized Biologically Active Systems. -P. Brodelius Industrial Applications of Immobilized Biocatalysts. - B. Solomon Starch Hydrolysis by Immobilized Enzymers. 

The wide spectrum of external conditions which can influence the conformational state of charged gels (the variation of these conditions can induce collapse or decollapse transition), makes these gels possible materials for data control devices of different types, absorbers, reactors and catalysts with regulated diffusion characteristics, carriers of immobilized enzymes, etc. The networks synthesized at high dilution are also new mechano-chemical systems which show very high sensitivity to external actions. 

Katchalski-Katzir, E., Kraemer, D.M. and Eupergit, C. (2000) a carrier for immobilization of enzymes of industrial potential. J. Mol. Catal. B Enzymatic,... 

Enzyme immobilized on the carrier was multiply rinsed from nonsorbed protein in distilled water then 0.2 M tris-HCl buffer (pH 8.0) was added to deposits and, finally, treated by... 

Acetylcholineesterase and choline oxidase Enzyme immobilized over tetra-thiafulvalene tetracyanoquinodi-methane crystals packed into a cavity at the tip of a carbon-fiber electrode. The immobilization matrix consisted of dialdehyde starch/glutaraldehyde, and the sensor was covered with an outer Nafion membrane. The ampero-metric performance of the sensor was studied with the use of FIA system. An applied potential of +100 mV versus SCE (Pt-wire auxiliary electrode) and a carrier flow rate of 1 mL/min. The Ch and ACh biosensors exhibited linear response upto 100 pM and 50 pM, respectively. Response times were 8.2 s. [97]... 

The amino group can be activated with bifunctional reagents. A commonly applied procedure is the introduction of an aldehyde function by the bifunctional reagent glutardialdehyde. The activated carrier can be used directly for the covalent bonding of the enzyme as shown in Fig. 7. Table 1 summarizes various examples of enzyme immobilization. 

For an immobilized enzyme it follows that a reduction in the rate of diffusion of a substrate to the active site of an enzyme will increase the apparent Km and reduce Fmax. The nature of the mass transfer effect depends on the fashion in which the enzyme is immobilized. Enzymes immobilized on the surface of a carrier will experience external mass transfer limitations between the bulk solution and the surface, whereas those entrapped within a porous matrix are also affected by internal mass transfer limitations due to the reduction in the rate of diffusion of substrate and products through the matrix. 

The number of carriers that have been used for enzyme immobilization constitute a long and ever-growing list. Both organic (naturcd and synthetic) and inorganic carriers have been employed. Some of the more frequendy used supports are listed in Table 1. 

Photolithographic methods, which play a key part in the fabrication of semiconductors, are potential candidates for the photo-patterning of small enzyme-immobilized membranes on a FET at its wafer stage. Ion-sensing FET devices with neutral carrier membranes sensitive to alkaline and alkaline earth metal... 

Consequently, it would actually be surprising if an enzyme immobilized on different carriers would behave the same on each of these different carriers. 

Figure 4.5. Enzyme immobilized onto a polyomithine carrier.

Many reviews and books on the immobilization of enzymes have been published during the last two decades [5, 11-20]. The intent of this part of the review is to explain the basic principles and to show recent developments of enzyme immobilization for the purpose of preparative biotransformation. The attachment of enzymes onto prefabricated artificial or natural carriers will be given special emphasis (see Sect. 3.2). 

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