Purification, catalytic, kinetic, thermodynamic characterization and stability profile of alkalophilic lipase from Streptomyces sp. SBLWN_MH2

Abstract

The current work intended to conduct a full descriptive study on lipase from a potential producer Streptomyces sp. SBLWN_MH2 (MG593538), that was previously isolated, to elucidate its characteristic features in an attempt to introduce a new industrial biocatalyst. The purified enzyme appeared as a single protein band of 24 kDa by SDS-PAGE. Among lipases from the genus Streptomyces, it was the most alkalophilic (optimum pH = 10.7; relative activity at pH 12 = 80%). Thermophilic tendency of the enzyme was clearly observed at optimum temperature 60 °C, and showed more than 96% relative activity at 70 °C. Km and Vmax values were 7.345 mM and 96.52 U/mg. The enzyme showed interested activities with inhibitors and organic solvents which highlighted its promising industrial application. The kinetic parameters of thermal inactivation were determined. The energies of activation and denaturation were 7.74 and 42.95 kJ/mol respectively. The temperature quotient (Q10) was 1.09 between 50 and 60 °C. Changes in enthalpy (ΔH) = 40.18, 40.10 and 40.02 kJ/mol at temperatures 60, 70 and 80 °C respectively. Changes in entropy (ΔS) at the same temperatures were −189.26, −190.24 and −189.73 J/mol.K, respectively while the change in Gibbs free energy (ΔG) was 103.21 kJ/mol at 60 °C with a tendency to increase to 105.35 and 106.99 kJ/mol at 70 and 80 °C respectively indicating the more resistance of enzyme against thermal unfolding at higher temperatures.