Immobilization and stabilization of alpha-galactosidase on Sepabeads EC-EA and EC-HA

Abstract

alpha-Galactosidase from tomato has been immobilized on Sepabead EC-EA and Sepabead EC-HA, which were activated with ethylendiamino and hexamethylenediamino groups, respectively. Two strategy was used for the covalent immobilization of alpha-galactosidase on the aminated Sepabeads: covalent immobilization of enzyme on glutaraldehyde activated support and cross-linking of the adsorbed enzymes on to the support with glutaraldehyde. By using these two methods, all the immobilized enzymes retained very high activity and the stability of the enzyme was also improved. The obtained results showed that, the most stable immobilized alpha-galactosidase was obtained with the second strategy. The immobilized enzymes were characterized with respect to free counterpart. Some parameters effecting to the enzyme activity and stability were also analyzed. The optimum temperature and pH were found as 60 degrees C and pH 5.5 for all immobilized enzymes, respectively. All the immobilized alpha-galactosidases were more thermostable than the free enzyme at 50 degrees C. The stabilities of the Sepabead EC-EA and EC-HA adsorbed enzymes treated with glutaraldehyde compared to the stability of the free enzyme were a factor of 6 for Sepabead EC-EA and 5.3 for Sepabead EC-HA. Both the free and immobilized enzymes were very stable between pH 3.0 and 6.0 and more than 85% of the initial activities were recovered. Under the identical storage conditions the free enzyme lost its initial activity more quickly than the immobilized enzymes at the same period of time. The immobilized alpha-galactosidase seems to fulfill the requirements for different industrial applications. (C) 2011 Elsevier B.V. All rights reserved.