Immobilized invertase studies on glass-ceramic support from coal fly ashes

Invertase was covalently immobilized on new coal fly ashes glass-ceramic support with zinc sulfate (GCSZn). The coupling process of proteins was demonstrated by X-ray diffraction (XRD). There was no change in the optimum pH (4.6) but optimum temperature increased from 55 degrees C for free invertase to 60 degrees C for immobilized derivative. The activation energy decreased after immobilization (37.31 +/- 3.40 kJ/mol) in spite of free invertase (51.34 +/- 5.21 kJ/mol). There was an improvement in the Michaelis-Menten constant for sucrose hydrolysis after immobilization being 15 times lower compared to that for free invertase (030 +/- 0.01 mmol). After ten reuses at 25 +/- 2 degrees C, the immobilized invertase lost only 9% of initial activity, but at the optimum temperature (60 degrees C), the activity decrease was about 70%, what it is economically feasible under energetic view point for industrial application. (C) 2012 Elsevier B.V. All rights reserved.