The influence of the intensity of agitation, reaction time, and enzyme concentration on the deactivation of a cellulase and a hemicellulase was studied in turbulent mixing environments. The activity of the cellulase and hemicellulase decreased with increasing shear rate and with elapsed mixing time. a sudden decrease in activity of cellulase after 10 minutes of mixing was observed. Although hemicellulase was found to be resistant to deactivation at a low shear rate, a higher shear rate deactivated the enzyme almost completely after 30 minutes. The influence of time on the reduction of activity was much more pronounced at higher shear rates. It is concluded that high shear or prolonged exposure to tow shear changes the molecular structures of the enzymes causing denaturation. As the concentration of the enzyme is increased, the rate of its deactivation can be expected to decrease.