Characterization of extracellular proteases from Pseudomonas sp. 16D4 and Dermacoccus sp. 17D6 isolated from arctic regions

摘要

In recent studies, cold-active enzyme has become another subject of interest. It can overcome the limitations of the classical industrial enzymes that normally require higher temperature to function. In this study, 16 bacteria isolated from the Arctic region were screened for their protease activity using Skim Milk agar plate. Two bacteria with lower hydrolysis coefficient (Hc) were selected, they were Pseudomonas sp. 16D4 (Hc = 0.339) and Dermacoccus sp. 17D6 (Hc = 0.331), and their proteases were produced using “Protease Specific Medium” and were further studied. Both bacteria produced proteases that are associated to growth and the maximal protease activity was reached at 30th hour and 24th hours of incubation, respectively. Protease produced by Pseudomonas sp. 16D4 remained stable at temperature ranging from 0oC to 70oC. Its optimum activity was detected at 0oC, pH 9 or 11 with Km value of 1.37 mg/mL and Vmax value of 243.90 Unit/L. As for Dermacoccus sp. 17D6, the protease activity remained stable at temperature ranging from 0oC to 40oC and its optimum condition for the assay was at 50oC, pH 7 or 9 with Km value of 0.66 mg/mL and Vmax value of 344.83 Unit/L. The SDS-PAGE and zymogram analysis further revealed that the molecular mass of the Pseudomonas sp. 16D4’s protease was 40 kDa. Whereas the size for the Dermacoccus sp. 17D6’s protease cannot be determined due to the negative result obtained in the zymogram analysis