The thermal inactivation of Bacillus subtilis alpha-amylase was studied in the presence and in the absence of Ca2+ at various temperatures. Inactivation rate constant (k), half-life time (t(1/2)), and activation energy (E-a) were determined to characterize the inactivation of the enzyme. Results obtained showed that the thermal inactivation of Bacillus subtilis alpha-amylase followed a first-order kinetics. The addition of Ca2+ had a good thermostabilizing effect on the enzyme. The stabilizing effect of Ca2+ is reflected by the increased values of the activation energy, which is about two times higher in the presence than that in the absence of 20 mM Ca2+, and the decreased values of the inactivation rat,2 constants. The desizing of the cotton fabrics was performed through steaming at 100 degrees C with Bacillus snbtilis alpha-amylase. The desizing efficiency seemed to be dependent on the concentration and pH value of the enzyme solution. It was found that through the steaming process with a-amylase, the desizing ratio of the cotton fabrics could be beyond 98% and little damage happened to the fibers of the fabrics. (c) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 109: 3733-3738, 2008.