Stability studies and kinetics of beta-1,3-glucanase from Trichoderma harzianum NCIM 1185 are reported. The critical parameters, pH and temperature, affecting the stability of beta-1,3-glucanase were optimized using response surface methodology. The optimal combination of pH and temperature were 3.6 and 41 degreesC, respectively. The stability of beta-1,3-glucanase was studied at various conditions of pH and temperature above the optimal conditions. Since the final activity was not zero, a non-first order deactivation model was used to explain the experimental data. Enzyme kinetic studies were carried out with and without inhibitors. CU2+ behaved as a noncompetitive-uncompetitive mixed inhibitor, whereas EDTA and NH4+ behaved as competitive-noncompetitive type mixed inhibitors during the hydrolysis of beta-1,3-glucan. (C) 2002 Elsevier Ltd. All rights reserved.