Abstract
Alpha-galactosidase has important applications in food processing, medicine and sugar beet industry. However, industrial application of enzymes, such as a-galactosidase, demands for efficient methods of enzyme immobilization. The aim of this work was to study the effect of the cross linking agent glutaraldehyde in the immobilization process of a commercial a-galactosidase StarMaxTM from Aspergillusniger in the ion exchange resin Duolite A-568. Firstly, four tests were carried out to determine the steps of the immobilization. The results showed better enzymatic activities for the immobilization processes without adding glutaraldehyde and the immobilization process using the support pre-activated with glutaraldehyde 1 % (v/v) followed by the enzymatic immobilization. A Central Composite Design was performed to study the best glutaraldehyde concentration and time of reticulation range in the immobilization process. Best conditions were obtained at low glutaraldehyde concentrations, where time did not have such effect. Finally, the operational stability of the immobilized a-galactosidase without the cross linking process was compared to that using the support pre-activated with glutaraldehyde 1 % (v/v). Glutaraldehyde was able to enhance the operational stability of the immobilized enzyme in 12 %, showing a residual activity of 86 % after 72 h in the reactor against 74 %. When immobilization was performed without the reticulation process, a-galactosidase lost 16 % of its initial activity in the first 2 h in the reactor against only 3 % for the enzyme immobilized in the pre-activated support.
