Enzyme immobilization entrapment

The first belief in the possibility of enzyme stabilization on a silica matrix was stated by Dickey in 1955, but he did not give experimental evidence, only mentioning that his experiments were unsuccessful [65]. A sol-gel procedure for enzyme immobilization in silica was first developed by Johnson and Whateley in 1971 [66]. The entrapped trypsin retained about 34 % of its tryptic activity observed in solution before the encapsulation. Furthermore, the enzyme was not released from the silica matrix by washing, demonstrating the increased stability and working pH range. Unfortunately, the article did not attract attention, although their method contained all the details that may be found in the present-day common approach. This was probably due to its publication in a colloid journal that was not read by biochemists. [Pg.82]

Among various enzyme immobilization protocols, entrapment in polymer membranes is a general one for a variety of transducers. Formation of a membrane from a solution of already synthesized polymer is simpler and reproducible compared to chemical polymerization. The simplicity of this immobilization procedure should provide reproducibility for the resulting biosensors the latter is strongly required for mass production. [Pg.450]

Some non-silica sol-gel materials have also been developed to immobilize bioactive molecules for the construction of biosensors and to synthesize new catalysts for the functional devices. Liu et al. [33] proved that alumina sol-gel was a suitable matrix to improve the immobilization of tyrosinase for detection of trace phenols. Titania is another kind of non-silica material easily obtained from the sol-gel process [34, 35], Luckarift et al. [36] introduced a new method for enzyme immobilization in a bio-mimetic silica support. In this biosilicification process precipitation was catalyzed by the R5 peptide, the repeat unit of the silaffin, which was identified from the diatom Cylindrotheca fusiformis. During the enzyme immobilization in biosilicification the reaction mixture consisted of silicic acid (hydrolyzed tetramethyl orthosilicate) and R5 peptide and enzyme. In the process of precipitation the reaction enzyme was entrapped and nm-sized biosilica-immobilized spheres were formed. Carturan et al. [11] developed a biosil method for the encapsulation of plant and animal cells. [Pg.530]

Several authors have attempted to optimize the HRP C conditions to remove phenols from aqueous solutions. Among the main parameters evaluated to improve the elimination of contaminants are the reactor configuration, enzyme immobilization, and the use of additives to protect the enzyme from entrapment in the precipitating polymers (Hamid and Khalil-ur-Rehman 2009). [Pg.115]

It was reported that PEGylated lipase entrapped in PVA cryogel could be conveniently used in organic solvent biocatalysis [279], This method for enzyme immobilization is more convenient in comparison to other types of immobilization that take advantage of enzyme covalent linkage to insoluble matrix, since the chemical step which is time consuming and harmful to enzyme activity is avoided. The application of this catalytic system to the hydrolysis of acetoxycoumarins demonstrated the feasibility of proposed method in the hydrolysis products of pharmaceutical interest and to obtain regioselective enrichment of one of the two monodeacetylated derivatives. [Pg.168]

Pharmaceutical production generally uses multipurpose equipment, and so entrapment behind a membrane would require significant capital expenditure on specialized equipment. In spite of this, the use of membrane reactors in biocatalysis represents an efficient method of enzyme immobilization, given the large molecular weight difference between enzymes (10-150 kDa) and most substrates (300-500 Da). The reader is referred to some recent reviews on the topic. [Pg.64]

Several papers have described the immobilization of enzymes by entrapment in foams. Especially polyurethane foam (PUF) has been widely used (Hu, Koras Stormo, 1993 Ferreriradias and Dafonseca, 1995 LeJeune et al., 1997). Hu et al. found that the... [Pg.255]

Many different types of techniques for protein immobilization have been developed using, in most cases, enzyme sensors. Early studies of enzyme biosensors often employed thick polymer membranes (thickness 0.01-1 mm) in which enzymes are physically entrapped or chemically anchored. The electrode surface was covered with the enzyme-immobilized polymer membranes to prepare electrochemical enzyme sensors. Although these biosensors functioned appropriately to... [Pg.147]

Immobilization onto a solid support, either by surface attachment or lattice entrapment, is the more widely used approach to overcome enzyme inactivation, particularly interfacial inactivation. The support provides a protective microenvironment which often increases biocatalyst stability, although a decrease in biocata-lytic activity may occur, particularly when immobilization is by covalent bonding. Nevertheless, this approach presents drawbacks, since the complexity (and cost) of the system is increased, and mass transfer resistances and partition effects are enhanced [24]. For those applications where enzyme immobilization is not an option, wrapping up the enzyme with a protective cover has proved promising [21]. [Pg.195]

Enzymes, when immobilized in spherical particles or in films made from various polymers and porous materials, are referred to as immobUized enzymes. Enzymes can be immobilized by covalent bonding, electrostatic interaction, crosslinking of the enzymes, and entrapment in a polymer network, among other techniques. In the case of batch reactors, the particles or films of immobilized enzymes can be reused after having been separated from the solution after reaction by physical means, such as sedimentation, centrifugation, and filtration. Immobilized enzymes can also be used in continuous fixed-bed reactors, fluidized reactors, and membrane reactors. [Pg.105]

Enzymes, immobilized, are attached to a solid support by adsorption or chemical binding or mechanical entrapment in the pores of a gel structure, yet retain most of their catalytic powers... [Pg.657]

Four methods have been developed for enzyme immobilization (1) physical adsorption onto an inert, insoluble, solid support such as a polymer (2) chemical covalent attachment to an insoluble polymeric support (3) encapsulation within a membranous microsphere such as a liposome and (4) entrapment within a gel matrix. The choice of immobilization method is dependent on several factors, including the enzyme used, the process to be carried out, and the reaction conditions. In this experiment, an enzyme, horseradish peroxidase (donor H202 oxidoreductase EC 1.11.1.7), will be imprisoned within a polyacrylamide gel matrix. This method of entrapment has been chosen because it is rapid, inexpensive, and allows kinetic characterization of the immobilized enzyme. Immobilized peroxidase catalyzes a reaction that has commercial potential and interest, the reductive cleavage of hydrogen peroxide, H202, by an electron donor, AH2 ... [Pg.390]

In recent years the electrochemistry of the enzyme membrane has been a subject of great interest due to its significance in both theories and practical applications to biosensors (i-5). Since the enzyme electrode was first proposed and prepared by Clark et al. (6) and Updike et al. (7), enzyme-based biosensors have become a widely interested research field. Research efforts have been directed toward improved designs of the electrode and the necessary membrane materials required for the proper operation of sensors. Different methods have been developed for immobilizing the enzyme on the electrode surface, such as covalent and adsorptive couplings (8-12) of the enzymes to the electrode surface, entrapment of the enzymes in the carbon paste mixture (13 etc. The entrapment of the enzyme into a conducting polymer has become an attractive method (14-22) because of the conducting nature of the polymer matrix and of the easy preparation procedure of the enzyme electrode. The entrapment of enzymes in the polypyrrole film provides a simple way of enzyme immobilization for the construction of a biosensor. It is known that the PPy-... [Pg.139]

Acetylcholineesterase and choline oxidase Enzymes were entrapped in a photo-cross-linkable polymer. Detection of H202 liberated from the enzyme reaction. The range of application was 20-750 pM for ACh. Response time was 2-4 min. The immobilized enzyme membranes were very stable, and stored in a dry state. [69]... [Pg.31]

For the repeated use of enzymes in such an analytical device, numerous techniques for enzyme immobilization including entrapment in hydrogels (membrane... [Pg.254]

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. [Pg.1393]

Bearing in mind technical application with scale-up, enzyme immobilization is a prerequisite. Since the large enzyme (ca. 180 kDa) is additionally linked with a dextran chain, it can be easily and economically immobilized by entrapment in calcium alginate [29, 94]. [Pg.180]

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