A search of an optimal carrier for immobilization of chitin deacetylase

Chitin deacetylase is an enzyme that can play an important role in enzymatic deacetylation of chitosan to obtain polymers with a lower degree of acetylation. As this enzyme has never been immobilized up to now, efforts were directed towards determining both the most suitable carrier and the best method of covalent attachment to the selected carrier. In the preliminary experiments several different carriers were tested that were based on acrylic, silica-gel, agarose, dextran or cellulose materials. The best results were obtained for cellulose-based Granocel matrix. DEAE- and NH₂-Granocel activated with divinyl sulfone or glutaraldehyde were chosen for optimization of the immobilization procedure and the carrier’s superstructure. It was found that covalent binding of chitin deacetylase on DEAE-Granocel-2000 via divinyl sulfone offers preparations with the highest activity and stability. The characteristics of the selected preparation and comparison with the native enzyme show that optimal conditions are close to those for the free enzyme: the optimal pH is 4.0 for both enzymes and the optimal temperatures are 55 °C and 50 °C for native and immobilized forms, respectively. The kinetics of chitosan deacetylation for both enzymes follow the Michaelis–Menten relationship, but significant differences in the values of the equation parameters were observed.