KINETICS OF GLUCOSE ISOMERIZATION TO FRUCTOSE BY IMMOBILIZED GLUCOSE-ISOMERASE IN THE PRESENCE OF SUBSTRATE PROTECTION

The activity of immobilized glucose isomerase of Streptomyces murinus has been tested batchwise under different conditions in order to gathe r the related kinetic parameters necessary to optimize an immobilized enzyme column for the continuous production of high fructose corn syru p (HFCS). To this purpose, the Briggs-Haldane model incorporating an a pparent first-order inactivation constant has been used with success. A comparison of the equilibrium constants and of the maximum theoretic al conversion yields calculated at different temperatures with those e stimated for the native enzyme demonstrates that the immobilization fa vours the transformation of glucose to fructose only at T > 70 degrees C, as a possible consequence of a combined effect of catalysis and eq uilibrium thermodynamics enhancement. Enzyme inactivation has also bee n tested at different temperatures and sugar concentrations to evaluat e the related kinetic parameters under different conditions of substra te protection.