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

α-Amylase was immobilized on zirconia via adsorption. The support and the immobilized enzymes were characterized using XRD, IR spectra and N2 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 N2 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. Km 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.