Optimization of protease activity of alkaliphilic bacterium isolated from soil of Ahvaz, Iran

Introduction and Objectives: Proteases are the hydrolytic enzymes which hydrolyze peptide bond between proteins with paramount applications in pharmaceutical and industrial sector. They produce protein, peptide fragments, and free amino acids. They can be intracellular or extracellular. Extracellular proteases are important for the hydrolysis of proteins in cell-free environments and enable the cell to absorb and utilize hydrolytic products. We isolated a bacterium from soil of Ahvaz, Iran which produces potent alkaline protease. The morphological, biochemical and 16S rDNA gene sequencing studies revealed that the isolated bacterium is Bacillus siralis strain PA02.Materials and Methods: We used skim milk agar to screen alkaline proteases. A halo (clear zone) around a colony could indicate protease activity. The enzyme’s activity was assayed by the caseinolytic method. By this way, the protease used casein as substrate and released tyrosine. We measured the absorbance of the tyrosine at 275nm.Results: The optimum activity of the enzyme from this organism was observed at pH 11.0, temperature 55 °C and was stable at pH values from 8 to 12 during the 30 minutes of incubation at 35 °C. Temperature stability ranged from 35 °C to 85 °C but the maximum stability was reached at 35 °C retaining 81% of the enzyme’s activity after 1 hour of incubation. The enzyme’s activity increased in the presence of ions like??2+, ??2+, ??+, and its activity decreased when ??2+, ??2+and ?+ were present.Conclusion: In conclusion, the activity and stability of this protease in the extreme pH range, its stability at high temperature, makes it attractive for industrial application.

Keywords:

Extracellular alkaline proteases , Enzyme stability , Bacillus siralis