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Abstract--We have made an experimental study of the isomerization of fructose and glucose by glucose isomerase in two forms: one soluble and the other immobilized by being fixed in a gel matrix. For the latter technique we used a fixed-bed differential reeirculation reactor, which allowed us to obtain comparable results to those we got with the enzyme dissolved within a batch reactor. We propose a simple method of comparing the results obtained in both systems, which permits us to determine the relative activity of each enzyme and also the effective diffusivity in the immobilized enzyme. The values obtained for the latter indicate a tortuosity factor of 2.04, which is lower than that generally found in porous solids but consistent with the results published in the literature for diffusion in gel particles.The application of our method to the results arrived at with the two systems studied confirms the validity of the kinetic model for glucose-fructose isomerization and has lead to our being able to determine both the kinetic constants for the reaction and their variation according to temperature.

We have studied the equilibrium and kinetics of fructose-to-glucose isomerhtion using a commercial immobilized glucose isomerase, Sweetzyme P (from NOVO), in a packed-bed recirculation reactor which enabled US to eliminate the influence of external-mass transfer and which could function as a differential reactor when a sufficient flow rate was used. 'Ihe results obtained have alsobeen comcted with regad tothe Muence of iaernal transport in the immobilized enzyme particles.Isomerization kinetics is a pseudo iirst-order reversible reaction in the ranges studied: 303-333 K, pH 7.5 and 0.5 to 2.0 moYL hexose concentrations. We compare our results with those found in the literature, and propose equations for the influence of temperature on the equilibrium and on the kinetic constants.Nous avons kNdik I'kquilibre et la cinktique de l'isomkrisation du fructose en glucose h l'aide d'une isodrase de glucose immobiliske commerciale, Sweetzyme P (de NOVO), dans un rcacteUr h recirculation h lit g a d ; ce rhcteur nous a permis d'kliminer l'influence du transfert de matibre externe et pouvait fonctionner comme t.eacteur diffkrential si on appliquait un dkbit suffisant. Les r&ultats obtenus ont kgalement ktt? ConigeS en ce qui concern I'influence du transport interne dans les particules d'enzyme immobilish.La cinktique d'isomkrisation est une rhction dversible du pseudo-premier order dans les gammes 6tudiQs, h savoir: 303-333 K, pH 7 3 et concentration d'hexose de 0.5 h 2.0 mom. Nous avons cornpark nos dsultats avec ceux de la litt6rature scientifique et nous pmposons des &pations pour I'innuenCe de la tempbme sur I'6qdibn et les constantes cinktiques.