Fig. 5.

(A) Effect of pH on keratinase activity. The pH profiles were determined in different buffers by varying pH values at 60℃. (▪), citrate buffer (pH 4~6); (□), NaHPO₄/Na₂HPO₄ buffer (pH 6~8); (•), Tris-HCl buffer (pH 7~9); (○), glycine/NaOH buffer (pH 9~11); (▴), NaHCO₃/NaOH buffer (pH 11~12). (B) Effect of temperature on the keratinase activity (♦) and on the thermal stability (○) of the purified keratinase. The enzyme was incubated in 100 mM Tris-HCl buffer (pH 8.0) at different temperatures for 15 min and the residual activity was determined as described in Materials and Methods.