Comparative study of methodologies for obtaining beta-glucosidase immobilized on dextran-modified silica

In this study, two procedures for the immobilization of beta-glucosidase on silica are compared. The first approach comprises a preliminary stabilization of beta-glucosidase by coupling with dextran dialdehyde and subsequent immobilization of the obtained beta-glucosidase dextran dialdehyde with aminopropylsilica. In the second approach, beta-glucosidase is immobilized on silica modified with a dextran-dialdehyde coating. Enzyme immobilized via coupling with dextran dialdehyde and subsequent attachment with aminopropylsilica show a remarkably enhanced thermostability. Enzyme immobilized by the alternative approach demonstrated an inferior thermoresistance. The difference in behavior of the immobilized enzyme obtained via these two methods can be explained considering the number of links between the enzyme and carrier. Enzyme immobilized on dextran dialdehyde-coated silica is fixed via a limited number of links. On the other hand, with soluble beta-glucosidase-dextran conjugates, the enzyme configuration is already stabilized via a high number of links with the dextran backbone. It is clear from this study that the sequence of reactions in immobilizing enzymes on silica support via a dextran-dialdehyde linker has a significant effect on the final properties. (C) 1996 by Elsevier Science Inc.