Popular matrices for enzyme and other immobilizations

Efficient immobilization of AGE and NAL enzymes onto functional amino resin as recyclable and high-performance biocatalyst

N-Acetylglucosamine-2-epimerase (AGE) and N-acetylneuraminic acid lyase (NAL) were immobilized for synthesis of N-acetylneuraminic acid (Neu5Ac) on three resins: Amberzyme oxirane resin (AOR), poly (styrene-co-DVB)-Br resin (PBR) and amino resin (AR). The loading capacity and immobilized enzyme activity showed that AR was the best carrier. Three methods of glutaraldehyde cross-linking were tested and simultaneous cross-linking and immobilization was demonstrated to be the best method. The functional properties of immobilized AGE and NAL were studied and compared to those of the free enzyme. The highest enzyme activities of free and immobilized AGE were obtained in 0.1 M potassium phosphate buffer at pH 7.5 and a temperature of 37 °C. Comparatively, the highest NAL activities were at pH 8.5. Meanwhile, an increase in K _m (from 1.14 to 1.31 mg·mL^-1 for AGE and from 1.05 to 1.25 mg·mL^-1 for NAL) and a decrease in V _max (from 177.53 to 106.37 µg·min^-1 mL^-1 for AGE and from 126.41 to 95.96 µg·min^-1 mL^-1 for NAL) were recorded after immobilization. The AR-glutaraldehyde-enzyme system exhibited better thermal stability than the free enzyme, and retained 72% of its initial activity even after eight repeated runs. The apparent activation energy (E _a) of the free and immobilized AGE (NAL) was 117.14 kJ·mol^-1 (124.21 kJ·mol^-1) and 78.45 kJ·mol^-1 (66.64 kJ·mol^-1), respectively, implying that the catalytic efficiency of the immobilized enzyme was restricted by mass-transfer rather than kinetic limit. Subsequently, Neu5Ac production from GlcNAc using immobilized enzymes in one reactor was carried out resulting 101.45 g·L^-1 of Neu5Ac and the highest conversion ratio of 82%. This method of enzyme immobilization may have a promising future for Neu5Ac production in industry.

Immobilization and characterization of benzoylformate decarboxylase from Pseudomonas putida on spherical silica carrier

If an adequate biocatalyst is identified for a specific reaction, immobilization is one possibility to further improve its properties. The immobilization allows easy recycling, improves the enzyme performance, and it often enhances the stability of the enzyme. In this work, the immobilization of the benzoylformate decarboxylase (BFD) variant, BFD A460I-F464I, from Pseudomonas putida was accomplished on spherical silica. Silicagel is characterized by its high mechanical stability, which allows its application in different reactor types without restrictions. The covalently bound enzyme was characterized in terms of its activity, stability, and kinetics for the formation of chiral 2-hydroxypropiophenone (2-HPP) from benzaldehyde and acetaldehyde. Moreover, temperature as well as pressure dependency of immobilized BFD A460I-F464I activity and enantioselectivity were analyzed. The used wide-pore silicagel shows a good accessibility of the immobilized enzyme. The activity of the immobilized BFD A460I-F464I variant was determined to be 70% related to the activity of the free enzyme. Thereby, the enantioselectivity of the enzyme was not influenced by the immobilization. In addition, a pressure-induced change in stereoselectivity was found both for the free and for the immobilized enzyme. With increasing pressure, the enantiomeric excess (ee) of (R)-2-HPP can be increased from 44% (0.1 MPa) to 76% (200 MPa) for the free enzyme and from 43% (0.1 MPa) to 66% (200 MPa) for the immobilized enzyme.

Adsorption and enzyme (beta-galactosidase and alpha-chymotrypsin): immobilization properties of gel fiber prepared by the gel formation of cellulose acetate and titanium iso-propoxide

We prepared a new composite gel fiber by the gel formation of cellulose acetate and titanium iso-propoxide. The fiber is harder than alginate gel; it is also stable in common solvents, phosphate solution, and electrolyte solutions over a wide range of pH from 3 to 10. The fiber shows amphoretic adsorption properties depending on pH, namely, it acts anionic with decreasing pH and cationic with increasing pH. However, the fiber had no adsorption property for a pyrogen endotoxin. The beta-galactosidase and alpha-chymotrypsin not retained in alginate gel were immobilized on the fibers by this method. The pH, temperature, and repeated run stabilities of the immobilized enzyme were compared to those of the native one. Copyright 1998 John Wiley & Sons, Inc.

Preparation of fibre-entrapped enzyme using cellulose acetate-titanium-iso-propoxide composite as gel matrix

Enzyme (uricase or invertase) was entrap-immobilized in gel fibre of cellulose acetate-TiO2 by using a gel formation of cellulose acetate and titanium iso-propoxide. The fibre is stable in common solvents, phosphate solution and electrolyte solution over a wide range of pH 4-10. The pH maximum of activity shifts to a more alkaline side compared to free enzyme, reflecting an amphoteric property of TiO2.

Bioreactor applications of glucose oxidase covalently bonded on pHEMA membranes

Glucose oxidase was immobilized onto poly(2-hydroxyethyl methacrylate) membranes by covalent bonding through epichlorohydrin. The highest immobilization efficiency was found to be 17.4%. The Km values were 5.9 and 8.8 mM for free and bound enzymes, respectively, and the Vmax values were 0.071 and 0.067 mM/min for free and bound enzymes. When the medium was saturated with oxygen Km was not altered significantly but Vmax was. The optimum pHs for the free and bound enzyme were determined to be 5 and 6, respectively, and the optimum temperature was 30 degrees C for both forms. The inactivation constant for the bound enzyme was found to be 1.7 x 10(-4) min-1.