Purification, characterization and immobilization of glucose isomerase from Streptomyces albaduncus

Glucose isomerase produced from Streptomyces albaduncus was purified to homogeneity by ammonium sulphate precipitation, followed by ion exchange DEAE-cellulose chromatography, and finally on DEAE-Sephadex A-50 chromatography. The molecular weight of the purified enzyme was estimated to be 54 kDa by sodium dodecyl sulphate polyacrylamide gel electrophresis (SDS-PAGE). The final preparation by the purification procedure had 10.3% final activity recovery and 13.3-fold purification. The optimum pH and temperature for GI activity were 7 and 70°C, respectively. In addition, the presence of the combination of Mg2+ and Co2+ ions (5 mM) improve the GI activity. Partially purified GI enzyme was immobilized by cross-linking with gluteraldahyde, adsorption on DEAE-Cellulose, and entrapment into polyacrylamide. Immobilization of GI enzyme caused sight decrease (3-19% reduction) in the enzymatic activity as compared to that of the non-immobilized enzyme. The maximum enzymatic activity (97%) and stability (88%) was obtained in the immobilized enzyme prepared by entrapment into polyacrylamide.   Key words: Glucose isomerase, Streptomyces albaduncus, purification, immobilization.