Immobilization of glucose isomerase to ion-exchange materials

Biochemical engineering of biocatalysts immobilized on cellulosic materials

Complete design of the optimum immobilized biocatalyst seems to still be a matter of the future. To be successful, it would require numerical determination of all significant parameters at each enzyme engineering phase, that is at the design of the carriers, immobilized biocatalysts and immobilized reactors. Future research trends should follow this strategy. For processing, cellulosic materials have been considered carriers that fulfill requests to an example model: they represent a unique family of carriers that cover a broad variety of physical and chemical properties, immobilizing techniques, and immobilized reactors as well. The reason for writing this review article was to test the reliability of such a processing and subsequently, to confront theoretical considerations with practical applications of biocatalysts immobilized on cellulose materials.

Immobilization of glucose isomerase onto granular chicken bone

Glucose isomerase was immobilized onto granular chicken bone (BIOBONE) by adsorption. The amount of activity bound relative to an equal amount of free enzyme was 32 +/- 1%, with the estimated specific activity decreasing from 11.1 +/- 0.7 to 3.9 +/- 0.5 U/mg protein with immobilization. Compared with the free enzyme, immobilized glucose isomerase showed a threefold increase in the Km for fructose and a fivefold decrease in Vmax. High operating temperatures were possible (greater than 55 degrees C), but continuous use and long-term storage studies showed gradual losses of activity. Both the binding and the activity of the bone-immobilized enzyme were highly resistant to treatments with detergent, ethanol, and KCl. Studies to determine mass transfer limitation effects on immobilized glucose isomerase showed that these were insignificant for this system.

Purification, Immobilization, and Some Properties of Glucose Isomerase from Streptomyces flavogriseus

Glucose isomerase (EC 5.3.1.5) produced from Streptomyces flavogriseus was purified by fractionation with (NH 4 ) 2 SO 4 and chromatography on diethylaminoethyl (DEAE)-cellulose and DEAE-Sephadex A-50 columns. The purified enzyme was homogeneous as shown by ultracentrifugation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Benzyl DEAE-cellulose, triethylaminoethyl-cellulose, and DEAE-cellulose were effective in the immobilization of partially purified glucose isomerase. Several differences in properties were found between purified soluble enzyme, immobilized enzyme (DEAE-cellulose-glucose isomerase), and heat-treated whole cells. Glucose and xylose served as substrate for the enzyme. Whole cells had the highest K m values for glucose and xylose; the soluble enzyme had the lowest values. The optimum temperature for activity of the soluble and immobilized enzymes was 70°C; that for whole cells was 75°C. The pH optimum for the three enzyme preparations was 7.5. Magnesium ion or Co 2+ was required for enzyme activity; an addition effect resulted from the presence of both Mg 2+ and Co 2+ . The enzyme activity was inhibited by Hg 2+ , Ag + , or Cu 2+ . The conversion ratio of the enzyme for isomerization was about 50%. The soluble and immobilized enzymes showed a greater heat stability than whole cells. The soluble enzyme was stable over a slightly wider pH (5.0 to 9.0) range than the immobilized enzyme and whole cells (pH 5.5 to 9.0). The molecular weight of the enzyme determined by the sedimentation equilibrium method was 171,000. A tetrameric structure for the enzyme was also indicated. After operating at 70°C for 5 days, the remaining enzyme activity of the immobilized enzyme and whole cells, which were used for the continuous isomerization of glucose in a plug-flow type of column in the presence of Mg 2+ and Co 2+ , was 75 and 55%, respectively. Elimination of Co 2+ decreased operational stability.