Colloid particles, produced by mixing H2SO4 and ZrOCl2 were treated with 3-aminopropyltriethoxysilane (3-APTES) and glutaraldehyde and deposited on a ceramic tube to form a dynamic membrane. alpha-Amylase was immobilized onto the membrane by means of covalent coupling to the glutaraldehyde pretreated colloids. The process, using 0.5% glutaraldehyde, produced an active dynamic membrane with an activity of 59.8 U/g wet gel. The specific activity of alpha-amylase on the membrane was 21.85 U/mg protein at its optimum pH 5.5 and 41 degrees C, compared with the highest specific activity, 1.91 U/mg protein, of the free enzyme at the optimum pH 6.6 and 63 degrees C. The membrane should be used at a temperature below 40 degrees C to maintain enzyme activity.