Glucose (xylose) isomerase production from thermotolerant and thermophilic bacteria

Glucose (xylose) isomerase (GI) is one of the most important industrial enzymes. It is used widely to catalyze the reversible conversion of D-glucose to D-fructose in vivo. The latter is used on a wide scale in the production of the high fructose corn syrup (HFCS) from corn starch. The great need of a thermostable GI, which is still active at higher temperatures (up to 90°C), opened the door to screen more microorganisms for the production of a more efficient industrial enzyme. Whole cells of 50 thermotole-rant/thermophilic bacterial isolates were used to evaluate their potential to produce GI when they were grown in broth medium (pH 7.0) containing D-xylose as a sole carbon source. Klebsiella and Pseudomonas showed the highest enzyme activity of 0.7; Bacillus came second with an activity of 0.3; while Acetobacter and Staphylococcus showed moderate activity of 0.3 for both, and Clostridium, Corynebacterium and Enterobacter showed the lowest enzyme activity of 0.2 each. The results reveal the need for optimizing the conditions for enhancing the production of the enzyme from Klebsiella and Pseudomonas isolates.Key words: Glucose isomerase, xylose isomerase, enzyme activity, Klebsiella, Pseudomonas