Effects of Temperature and pH on the Stability of Protease Produced by Alcaligenes faecalis P2

Background: Bacterial proteases represent a group of very important industrial enzymes. They are involved in the hydrolysis of peptide bond found in protein. Industrial application of bacterial proteases has been limited by low yield and instability at biotechnological process conditions. This study was design to investigate the effect of temperature and pH on the stability of protease produced by Alcaligene faecalis strain P2.

Methodology: Protease-producing bacteria were isolated from beans effluent-impacted soil and screened for protease production on Casein agar plate. Protease assay was carried out following standard method for protease determination and the stability of the protease produced was investigated over temperature range of 20 to 90 oC and pH range of 3 to 12. The protease-producing bacterium was identified using its molecular characteristics.

Results: Protease assay result showed that the amount of tyrosine released by one unit of the crude enzyme was 0.176 µmol/mL resulting in 0.19 U/mL protease activity. Stability studies showed that the protease had wide spectrum of pH and temperature stability. The protease was most stable at pH 9 and temperature of 40 oC after 30 min. Maximum protease activity of 1.259 U/mL was recorded with pH 9 after 30 min. The protease-producing bacterium was classified as Alcaligene faecalis P2 based on phylogenetic analysis of its 16S gene analysis. The sequences have been submitted to GenBank under the accession number MZ477004.

Conclusion: This study therefore has demonstrated that beans effluent-impacted soil harbours protease producing bacteria with high industrial potentials. In addition, the study revealed that the protease produced in this study can retain its activity over wide temperature and pH.