Research Information System
ICEST 2011, Aydın, Turkey, 12 May 2011, vol.1, pp.45
D-xylose isomerase (D-xylose ketol isomerase; E.C. 5.3.1.5) catalyzes the reversible isomeration of D-glucose and D-xylose to D-fructose and D-xylulose, respectively. Isomerization of glucose to fructose is commercial importance in the production of high fructose corn syrup (HFYC). Xylulose,formed by the enzymatic isomerzation of xylose, can be ultimately fermented to ethanol by conventional yeasts. Bioconversion of renewable biomass to fermentable sugars and ethanol is important in wiev of the rapid depletion of fossil fuels. Because of the industrial value of D-xylose isomerase; microbial sources, biochemical properties and immobilization of the enzyme have been extnsively studying [1]. In the present study, the D-glucoselD-xylose isomerase was purified from a thermophilic bacterium, Geobacillus thermodenitrificans TH2, by using a Q-Sepharose ion exchange column and characterized. The purified enzyme was observed as a single band on native polyacrylamide gel electrophoresis. In the presence of D-glucose as a substrate, the optimum temperature and pH of the enzyme we re found to be 80 "C and 7.5, respectively. The purified enzyme was extremely stable , in pH 7.5 and 9.0 after 72 ho ur incubation at 4°C and 50°C. When the thermal stability profile of the purified enzyme was analyzed, it was determined that the enzyme was extremely stable 4 mounts and 4 days at 4°C and 50°C, respectively. The Km and Vmax values of the purified enzyme were calculated as 0,032M and 4,684U/mg protein, respectıvely, from the Lineweaver-Burk plot . Additionally, it was detected that some metal ions affect the enzyme activity at different rates.As a result, G. thermodenitrificans TH2 had good stability at pH 7.5 and 4 "C. In addition this enzyme has similar features in terms of Km and Vmax values were shown to be compatible with the literature.