Characterization of a thermostable glucose isomerase with an acidic pH optimum from Acidothermus cellulolyticus

The glucose isomerase (GI) gene from the Acidothermus cellulolyticus 11B was cloned and overexpressed in Escherichia coli. The recombinant protein was purified to electrophoretical homogeneity by affinity chromatography using Chelating Sepharose Fast Flow resin. The enzyme activity was maximal at 80 °C and pH 6.5 while being significantly enhanced by Co2+ and Mg2+. The enzyme was determined as thermostable and weak-acid stable. These findings indicated that the GI from A. cellulolyticus 11B is appropriate for use as a new source of high-fructose corn syrup (HFCS) producing enzyme.