Enzymes covalently bound to polyacrylic and polymethacrylic copolymers

Agarose and Its Derivatives as Supports for Enzyme Immobilization

Agarose is a polysaccharide obtained from some seaweeds, with a quite particular structure that allows spontaneous gelation. Agarose-based beads are highly porous, mechanically resistant, chemically and physically inert, and sharply hydrophilic. These features-that could be further improved by means of covalent cross-linking-render them particularly suitable for enzyme immobilization with a wide range of derivatization methods taking advantage of chemical modification of a fraction of the polymer hydroxyls. The main properties of the polymer are described here, followed by a review of cross-linking and derivatization methods. Some recent, innovative procedures to optimize the catalytic activity and operational stability of the obtained preparations are also described, together with multi-enzyme immobilized systems and the main guidelines to exploit their performances.

Inorganic materials as supports for covalent enzyme immobilization: methods and mechanisms

Several inorganic materials are potentially suitable for enzymatic covalent immobilization, by means of several different techniques. Such materials must meet stringent criteria to be suitable as solid matrices: complete insolubility in water, reasonable mechanical strength and chemical resistance under the operational conditions, the capability to form manageable particles with high surface area, reactivity towards derivatizing/functionalizing agents. Non-specific protein adsorption should be always considered when planning covalent immobilization on inorganic solids. A huge mass of experimental work has shown that silica, silicates, borosilicates and aluminosilicates, alumina, titania, and other oxides, are the materials of choice when attempting enzyme immobilizations on inorganic supports. More recently, some forms of elemental carbon, silicon, and certain metals have been also proposed for certain applications. With regard to the derivatization/functionalization techniques, the use of organosilanes through silanization is undoubtedly the most studied and the most applied, although inorganic bridge formation and acylation with selected acyl halides have been deeply studied. In the present article, the most common inorganic supports for covalent immobilization of the enzymes are reviewed, with particular focus on their advantages and disadvantages in terms of enzyme loadings, operational stability, undesired adsorption, and costs. Mechanisms and methods for covalent immobilization are also discussed, focusing on the most widespread activating approaches (such as glutaraldehyde, cyanogen bromide, divinylsulfone, carbodiimides, carbonyldiimidazole, sulfonyl chlorides, chlorocarbonates, N-hydroxysuccinimides).

A novel polyacrylamide-type support prepared by p-benzoquinone activation

A new and simple method for the activation of polyacrylamide gels using p-benzoquinone is described. The optimal conditions of activation have been elaborated. The activated support could be successfully applied to the immobilization of ligands having nucleophilic groups active over a broad pH range.

Effect of immobilization on stability and properties of N-acetyl-beta-D-hexosaminidase from Turbo cornutus

A mixture of glycosidases from the liver of the gastropod Turbo cornutus was co-immobilized with bovine serum albumin and glutaraldehyde, and then cast as membranes. The properties of immobilized N-acetyl-beta-D-hexosaminidase were studied. The recovery of N-acetyl-beta-D-hexosaminidase after immobilization was unaffected by increasing the concentration of glutaraldehyde, but was decreased by increasing the bovine serum albumin concentration. The immobilized enzyme showed enhanced resistance towards proteolytic and thermal inactivation. While the pH optimum for the soluble enzyme was 4.0, a bimodal pH curve with optima at 3.4 and 5.0 was observed after insolubilization. This bimodality was abolished when the immobilized enzyme was assayed in the presence of M NaCl. The Km values, for p-nitrophenyl 2-acetamido-2-deoxy-beta-D-glucopyranoside, of the immobilized isoenzymes of N-acetyl-beta-D-hexosaminidase were larger than those of their soluble counterparts. No loss of activity could be detected in the membrane after using it for 24 consecutive assays or after storage for at least 50 days at 4 degrees.