title: Detergent-, solvent- and salt-compatible thermoactive alkaline serine protease from halotolerant alkaliphilic Bacillus sp. NPST-AK15: purification and characterization.
abstract: Alkaline protease produced by the halotolerant alkaliphilic Bacillus sp. strain NPST-AK15 was purified to homogeneity by the combination of ammonium sulfate precipitation, anion-exchange and gel permeation chromatography. The purified enzyme was a monomeric protein with an estimated molecular weight of 32 kDa. NPST-AK15 protease was highly active and stable over a wide pH range, with a maximal activity at pH 10.5. The enzyme showed optimum activity at 60 °C and was stable at 30-50 °C for at least 1 h. Thermal stability of the purified protease was substantially improved by CaCl2 (1.1- to 6.6-fold). The K m, V max and k cat values for the enzyme were 2.5 mg ml(-1), 42.5 µM min(-1) mg(-1), and 392.46 × 10(3) min(-1), respectively. NPST-AK15 protease activity was strongly inhibited by PMSF, suggesting that the enzyme is a serine protease. The enzyme was highly stable in NaCl up to 20 % (w/v). Moreover, the purified enzyme was stable in several organic solvents such as diethyl ether, benzene, toluene, and chloroform. In addition, it showed high stability and compatibility with a wide range of surfactants and commercial detergents and was slightly activated by hydrogen peroxide. These features of NPST-AK15 protease make this enzyme a promising candidate for application in the laundry and pharmaceutical industries.
authors.affiliation: Department of Botany and Microbiology, College of Science, King Saud University, Riyadh, 11451, Kingdom of Saudi Arabia, ashebl@ksu.edu.sa.
authors.forename: Abdelnasser S S
authors.initials: AS
authors.lastname: Ibrahim
authors.forename: Ali A
authors.initials: AA
authors.lastname: Al-Salamah
authors.forename: Yahya B
authors.initials: YB
authors.lastname: El-Badawi
authors.forename: Mohamed A
authors.initials: MA
authors.lastname: El-Tayeb
authors.forename: Garabed
authors.initials: G
authors.lastname: Antranikian
mesh_terms: D001407:Bacillus / Q000201:enzymology*; D001426:Bacterial Proteins / Q000737:chemistry*; D002122:Calcium Chloride / Q000737:chemistry; D003902:Detergents / Q000737:chemistry; D004795:Enzyme Stability; D006358:Hot Temperature; D054712:Salinity; D057057:Serine Proteases / Q000737:chemistry*
chemical_list: D001426:Bacterial Proteins; D003902:Detergents; D057057:Serine Proteases; D002122:Calcium Chloride