Proteases are a broad family of hydrolytic enzymes with various applications in chemical, cosmetics, and
pharmaceutical industries. Owing to their physiological necessity, proteases are found in diverse sources including
microorganisms. Our objective study was to search for a high quality and inexpensive source for the production of
microbial proteases under different culture and growth conditions. Also, we aimed to characterize microbial proteases.
Proteases-producing bacteria were isolated from soil samples collected from a poultry waste site. Soil samples were
inoculated in skimmed agar media and 48 h later, colonies producing clear zones were selected as the source of
microorganisms producing enzyme. The isolates were used to inoculate liquid media and the clear supernatant was taken
as a crude for enzyme preparation. The enzyme was isolated and purified with ammonium sulfate at 60-80% saturation
followed by dialysis. Subsequently, characterization of the enzyme fraction with the highest activity was carried out. The
results indicated that the isolated enzyme with (60-80%) fractionation of ammonium sulfate exhibited the highest
specific activity. In addition, the optimal temperature for enzyme activity was determined at 70ºC at pH values of 0.05M
of acetate buffer 3.6 and 0.05M of glycine-NaOH buffer 10.0. Finally, the kinetic parameters (Michaelis–Menten
constant, Km and maximal reaction velocity, Vmax) were calculated as 0.11 μmole/ml and 0.5x104 nmole of
tyrosine/ml/hour, respectively. In conclusion, our findings provide evidence that the isolated bacteria represent a rich
source of thermostable proteases. Indeed, more studies are still required to obtain such proteases in a purified form