Carriers for Enzyme Immobilization

An enormous number of carriers are available for the immobilization of enzymes 

Organic - synthetic polymer Organic - biopolymer Inorganic 

When the mass of carrier material is large relative to that of the enzyme, the physical and chemical properties of the carrier (Table 6-5) will, in large part, determine properties of the resultant immobilized enzyme. Often, the carrier will impart mechanical strength to the enzyme, allowing repetitive recovery by simple filtration of the solid particles and reuse of the enzyme. The degree of porosity and pore volume will determine the resistance to diffusion and molecular size selectivity of the biocatalyst. When used in non-aqueous media, dispersion of the enzyme over a large surface area can greatly increase its activity. Table 6-3 summarizes many of the key properties and considerations for enzyme carrier materials. 

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However, to our knowledge, most previous studies of enzyme-catalyzed polymerizations have avoided temperatures > 90 oC, which is likely due to thermal deactivation of enzyme catalyst (13-15). It has been found that enzyme immobilization can improve the stability and recyclablity of native enzyme (16). Silica particles, activated by methanesulfonic acid, are effective and economic inorganic carriers for enzyme immobilization (17). Herein, we present a minireview of our works about immobilized porcine pancareas lipase on silica particles (IPPL) for polymer synthesis, such as polycarbonates, polyesters, polyphosphates and their copoljmiers. 

Active immobilized enzyme detoxification of pesticides in production waste-waters Active immobilized enzyme deacylation of benzylpenicillin in a continuous four-stage stirred-tank reactor Investigation of properties of the active immobilized enzyme Investigation of new carriers for enzyme immobilization... 

The high permeability of carboxyl CP in combination with their considerable selectivity of bonding protein macromolecules have made it possible to use them as carriers for the immobilization of proteins and enzymes with the aim of protection against some physiological factors (e.g., the pH of the medium). 

Poly (p-nitrophenyl acrylate)-coated wide-pore glass (WPG) was also used as an activated carrier for the immobilization of biospecific ligands and enzymes, A detailed description of properties of these sorbents and catalysts as well as some specific features of their functioning is given in Sect. 6. 

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... 

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. 

The molecular sieves ITQ-1 and ITQ-6 with low aluminum content have been used as supports for enzyme immobilization the zeolites exhibit a very ordered external surface and good thermal stability. Different enzymes including Penicillin G acylase were stabilized via electrostatic and covalent interactions on zeolite carriers. The possibility of using molecular sieves for processes involving enzymes as catalysts or sensors has been demonstrated.[52]... 

In this example, lipase is immobilized on different carbon monoliths and applied in a transesterification reaction in toluene. The biocatalysts are compared in terms of carrier preparation, enzyme immobilization, and performance. A commercially available immobilized lipase is used as a comparison. A convenient tool to compare monolithic biocatalysts is the monolithic stirrer reactor (MSR), consisting of two monoliths that have the catalyst immobilized on the wall of their channels. These monoliths work as stirrer blades that can easily be removed from the reaction medium, thereby eliminating the need for a filtration step after reaction [37]. 

Three kinds of silica particles with different sizes (150-250 pm, 75-150 jim and 1 pm) were selected as carriers for PPL immobilization to study the relationships between the carrier size of immobilized enzyme, the catalytic activity for ring-opening copolymerization and the polymer yield. The highest M of 26400 of poly(BTMC-co-DTC) was obtained at around 0.1 wt% of IPPL with size of 75-150 pm. Moreover, the M of poly(BTMC-co-DTC) decreased rapidly with the increasing of IPPL concentration. 

The use of polymeric carriers as immobilizing media has been described. Spherical macroporous reactive carriers capable of forming covalent bonds with amino-acids and proteins have been prepared by suspension copolymerization of 2-hydroxyethyl methacrylate, ethylene dimethaciylate, and 4-nitrophenyl esters of methacrylic acid, and by suspension copolymerization of methacryloyl derivatives of glycine, /3-alanine, and 6-aminohexanoic acid. The carriers were reported to be suitable for enzyme immobilization. 

Enzymes are exploited as catalysts in many industrial, biomedical, and analytical processes. There has been considerable interest in the development of carrier systems for enzyme immobilization because immobilized enzymes have enhanced stability compared to soluble enzymes, and can easily be separated from the reaction. This leads to significant savings in terms of reduced enzyme consumption, and the ability to use such enzymes in continuous processes. The activity and stability of enzymes depends largely on the particular operating and storage conditions, and is strongly influenced by factors such as the chemical environment, temperature, pH, and solvent properties. Most enzymes are water soluble and a certain amount of water is always required for their solubilization. Additionally, many enzymes require the presence of a cofactor, which may be attached firmly to the enzyme or may need to be added separately as a coenzyme. When the immobilization of an enzyme... 

Despite the advantages of enzymes immobilized on noncatalytic matrices, the yield and productivity of the reaction can be reduced simply due to the presence of the noncatalytic mass of the carrier. There has therefore been much interest in the development of carrier-free systems, in which enzyme molecules are linked to each other to form large complexes. These are inherently immobilized because individual enzyme molecules are no longer free to diffuse in solution, but they are largely undiluted by inert molecules and therefore retain a greater degree of activity than carrier-bound enzymes. This article discusses strategies for enzyme immobilization in carrier-based and carrier-free systems and considers some of their major applications. 

In this type of protein immobilization, reactions involve the acylation of an NH2 group on a protein or an enzyme by pendent groups of the carrier such as azide, acid anhydride, carbodiimide, sulfonyl chloride, and hydroxysuccinimide esters. Copolymers of acrylamide and maleic anhydride have been useful for enzyme immobilization through the acid anhydride reaction with the enzyme. This system of... 

Other work on polymerization in particulate form has included the preparation of polycyanoacrylate nanocapsules as potential lysomotropic carriers, the encapsulation of pancreatic islet cells in hydrogels, " suspension polymerization of glycidyl methacrylate-2-hydroxypropylene dimethacrylate copolymers as hydrophilic macroporous spheres for enzyme immobilization, and the synthesis of macro-porous hydrogels as potential haemoperfusion adsorbents. ... 

Rucka, M., and B. Turkiewicz. 1990. Ultrafiltration Membranes as Carriers for Lipase Immobilization. Enzyme and Microbial Technology 12 (l) 52-55. 

Grasset, L., Cordier, D. and Ville A. (1977) Woven silk as a carrier for the immobilization of enzymes, Biotechnol Bioeng. 19, 611-618. 

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