Immobilization of α-amylase on zirconia:: A heterogeneous biocatalyst for starch hydrolysis

alpha-Amylase was immobilized on zirconia via adsorption. The support and the immobilized enzymes were characterized using XRD, IR spectra and N-2 adsorption studies. The efficiency of immobilized enzymes for starch hydrolysis was tested in a batch reactor. The effect of calcination temperatures on properties of the support as well as upon immobilization was studied. From XRD, IR and N-2 adsorption studies it was confirmed that the enzyme was adsorbed on the external surface of the support. pH, buffer concentration and substrate concentration had a significant influence on the activity of immobilized enzyme. Immobilization improved the pH stability of the enzyme. The Michaelis-Menten kinetic constants were calculated from Hanes-Woolf plot. K-m for immobilized systems was higher than the free enzyme indicating a decreased affinity by the enzyme for its substrate, which may be due to interparticle diffusional mass transfer restrictions. (c) 2006 Elsevier B.V. All rights reserved.