Characterization of thermo-solvent stable protease fromHalobacillussp. CJ4 isolated from Chott Eldjerid hypersaline lake in Tunisia

Abstract

About 110 newly isolated halophilic and halotolerant bacteria were screened for protease production. A moderately halophilic strain (CJ4), isolated from Chott Eldjerid Hypersaline lake in Tunisia, showed the highest activity on agar plate and was then selected. The biochemical and physiological characterization of the isolate along with the 16S rRNA sequence analysis placed it in the genus Halobacillus. Protease production was maximal at 120 g/L NaCl (2 M) and it started from the post-exponential phase reaching a maximum level at the early decline phase of bacterial growth. Protease activity was optimal at 0.4 M NaCl, pH 9 and 45 °C. It showed an excellent stability over wide ranges of temperatures (30-60 °C), NaCl concentrations (0-5 M), and pH values (5-10), which make it a good candidate for industrial applications at harsh conditions. Crude protease was strongly inhibited by PMSF revealing the dominance of serine proteases. Protease activity exhibited high stability in the presence of several organic solvents and detergent additives. These findings make Halobacillus sp. CJ4 protease with a great interest for many biotechnological applications at high salt or low water content such as peptide synthesis and detergent formulation.

Detergent‐Compatible Robust Alkaline Protease from Newly Isolated Halotolerant Salinicoccus sp. UN‐12

“…The optimum temperature of the studied protease was higher than those previously reported for proteases from halophilic/halotolerant bacteria [15,18,[22][23][24]. The outcomes related to the enhancement of protease activity in the presence of calcium ions are in agreement with former reports on the thermal stability of temperature-sensitive proteases by the addition of Ca 2?…”

“…Some ''thick'' systems consist of high salt concentration, whereas ''thin'' systems contain very low NaCl concentrations [35,36]. The salttolerant nature of the studied enzyme suggests its potential as a promising candidate for several biotechnological processes involving the use of high salt concentrations [15,37]. Additionally concerning the salt stability, the findings represented in Fig.…”

“…The Halobacillus sp. CJ4 showed growth over a wide range of NaCl concentrations 0-240 g/L (0-4.15 mol/L) with a maximum growth rate at 50 g/L NaCl (0.87 mol/L), while maximum protease production was observed at 120 g/L NaCl (2.08 mol/L) [15]. These reports on proteases from halophilic/halotolerant microbes suggested that there is a wide difference in the optimum salt concentration for production and growth.…”

“…CJ4. [15], Bacillus sp. NPST-AK15 [17], Bacillus subtilis BLK-1.5 [18], and Bacillus iranensis (X5B) [19].…”

“…The outcomes related to the enhancement of protease activity in the presence of calcium ions are in agreement with former reports on the thermal stability of temperature-sensitive proteases by the addition of Ca 2? [15,17,25].…”