Figure 4.

Effect of pH on the activity (a) and stability (b) of the extracellular proteases of A. niger I1 strain. pH optima were determined by incubating the crude enzyme with the substrate at different pH values at 60°C. The maximum activity obtained at pH 3.0 with hemoglobin as substrates was considered to be 100%. The pH stability was determined by incubating the crude enzyme in different buffers for 1 h at 4°C, and the residual activity was measured at pH 3.0 and 60°C with hemoglobin as a substrate. The activity of the enzyme before incubation was taken as 100%.