Purification and Characterization of a New Thermostable, Haloalkaline, Solvent Stable, and Detergent Compatible Serine Protease fromGeobacillus toebiiStrain LBT 77

Abstract

A new thermostable, haloalkaline, solvent stable SDS-induced serine protease was purified and characterized from a thermophilicGeobacillus toebiiLBT 77 newly isolated from a Tunisian hot spring. This study reveals the potential of the protease fromGeobacillus toebiiLBT 77 as an additive to detergent with spectacular proprieties described for the first time. The protease was purified to homogeneity by ammonium sulfate precipitation followed by Sephadex G-75 and DEAE-Cellulose chromatography. It was a monomeric enzyme with molecular weight of 30 kDa. The optimum pH, temperature, and NaCl for maximum protease activity were 13.0, 95°C, and 30%, respectively. Activity was stimulated by Ca2+, Mg2+, DTNB,β-mercaptoethanol, and SDS. The protease was extremely stable even at pH 13.25, 90°C, and 30% NaCl and in the presence of hydrophilic, hydrophobic solvents at high concentrations. The high compatibility with ionic, nonionic, and commercial detergents confirms the utility as an additive to cleaning products. Kinetic and thermodynamic characterization of protease revealedKm=1 mg mL−1,  Vmax=217.5 U mL−1,Kcat/Km=99 mg mL−1 S−1,Ea=51.5 kJ mol−1, andΔG⁎=56.5 kJ mol−1.