An extracellular thermostable alkaline serine protease enzyme from Aeribacillus pallidus C10 (GenBank No: KC333049), was purified 4.85 and 17. 32-fold with a yield of 26.9 and 19.56%, respectively, through DE52 anion exchange and Probond affinity chromatography. The molecular mass of the enzyme was determined through sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), with approximately 38.35 kDa. The enzyme exhibited optimum activity at pH 9 and at temperature 60 degrees C. It was determined that the enzyme had remained stable at the range of pH 7.0-10.0, and that it had preserved more than 80% of its activity at a broad temperature range (20-80 degrees C). The enzyme activity was found to retain more than 70% and 55% in the presence of organic solvents and commercial detergents, respectively. In addition, it was observed that the enzyme activity had increased in the presence of 5% SDS. K-M and V-max values were calculated as 0.197 mg/mL and 7.29 lmol. mL(-1). min(-1), respectively.