title: Characterization of halo-alkaline and thermostable protease from Halorubrum ezzemoulense strain ETR14 isolated from Sfax solar saltern in Tunisia.
abstract: A total of 54 halophilic strains were isolated from crystallizer TS18 (26 strains) and non-crystallizer M1 (28 strains) ponds and screened for their ability to produce protease, amylase, and lipase activities. Enzymatic assays allowed the selection of thirty-two active strains, among them, the ETR14 strain from TS18 showed maximum protease production yields and therefore, selected for further analysis. The results from 16S rRNA gene sequence analysis revealed that the strain belonged to Halorubrum ezzemoulense (Hrr. ezzemoulense) species. Further results indicated that optimum growth and protease production yields were obtained with 10-15% NaCl concentrations in the DSC-97 medium. The enzyme was also able to maintain high levels of protease activity at salt concentrations of up to 25%. While readily available carbon sources were noted to significantly reduce protease production, the combination between yeast extract and peptone enhanced protease excretion, which reached a maximum of 284 U ml(-1) at the end of the exponential growth phase. The enzyme exhibited optimum activity at pH 9 and 60 °C. The halophilic protease retained 87% of its initial activity after 1 h incubation at 70 °C and showed high stability over a wide range of pH, ranging from 7 to 10. This protease exhibited good temperature, pH, and salinity tolerance, which distinguishes it from other proteases previously described from other members of the holoarchaea genera and makes it a promising candidate for application in various industries.
authors.affiliation: Faculté des Sciences de Sfax, Université de Sfax, Unité Biodiversité et Ecosystèmes Aquatiques Environnementaux (UR/11ES72) Sfax, Tunisia.
authors.forename: Donyez Frikha
authors.initials: DF
authors.lastname: Dammak
authors.affiliation: Faculté des Sciences de Sfax, Université de Sfax, Unité Biodiversité et Ecosystèmes Aquatiques Environnementaux (UR/11ES72) Sfax, Tunisia.
authors.forename: Salma Masmoudi
authors.initials: SM
authors.lastname: Smaoui
authors.affiliation: Faculté des Sciences de Sfax, Université de Sfax, Unité Biodiversité et Ecosystèmes Aquatiques Environnementaux (UR/11ES72) Sfax, Tunisia.
authors.forename: Fadoua
authors.initials: F
authors.lastname: Ghanmi
authors.affiliation: Faculté des Sciences de Sfax, Université de Sfax, Unité Biodiversité et Ecosystèmes Aquatiques Environnementaux (UR/11ES72) Sfax, Tunisia.
authors.forename: Ines
authors.initials: I
authors.lastname: Boujelben
authors.affiliation: Faculté des Sciences de Sfax, Université de Sfax, Unité Biodiversité et Ecosystèmes Aquatiques Environnementaux (UR/11ES72) Sfax, Tunisia.
authors.forename: Sami
authors.initials: S
authors.lastname: Maalej
mesh_terms: D000681:Amylases / Q000378:metabolism; D019641:DNA, Archaeal / Q000235:genetics; D004275:DNA, Ribosomal / Q000235:genetics; D004789:Enzyme Activation; D004795:Enzyme Stability; D055352:Halorubrum / Q000201:enzymology* / Q000302:isolation & purification*; D006863:Hydrogen-Ion Concentration; D008049:Lipase / Q000378:metabolism; D010447:Peptide Hydrolases / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism*; D061005:Ponds / Q000382:microbiology; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D054712:Salinity; D014416:Tunisia
chemical_list: D019641:DNA, Archaeal; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S; D008049:Lipase; D000681:Amylases; D010447:Peptide Hydrolases
keywords: 16S rRNA; Halophilic protease; Halorubrum genus; Hydrolases; Marine solar saltern; Phylogeny