Characterization of an extracellular thermophilic alkaline esterase produced by Bacillus subtilis DR8806

This work is a report of the characterization of an alkaline lipolytic enzyme isolated from Bacillus subtilis DR8806. The extracellular extract was concentrated using ammonium sulfate, and ultrafiltration. The active enzyme was purified by Q-sepharose ion exchange chromatography. The molecular mass of the enzyme was estimated to be 60.25 kDa based on SDS-PAGE (sodium dodecyl sulfate polyacrylamide gel electrophoresis). The optimum pH and temperature of this enzyme were observed to be 8.0 and 50 °C, respectively. The enzyme exhibited a half-life of 72 min at its optimum temperature. It was stable in the presence of metal ions (10 mM) such as Ca2+, K+ and Na+, whereas Cu2+, Fe2+, Zn2+, Mn2+, Co2+, Mg2+ and Hg2+ were found to have inhibitory effects. However, the enzyme activity was not affected significantly by 1% Triton X-100. The study of substrate specificity showed that the purified enzyme has a preferential specificity for small ester of p-nitrophenyl acetate (C2), and it was the most efficiently hydrolyzed substrate as compared to the other esters. The kinetic parameters showed that the enzyme has Km of 4.2 mM and Vmax of 151 μmol min−1 mg−1 for p-nitrophenyl acetate. The hydrolysis rates of the fluorescence substrates were increased in the presence of the purified enzyme. Regarding the features of the enzyme, it may be utilized as a novel candidate for industrial applications.

Figure optionsDownload as PowerPoint slideHighlights
► An alkaline lipolytic metalloenzyme from Bacillus subtilis DR8806 was characterized.
► The optimum pH and temperature of this enzyme were observed to be 8.0 and 50 °C.
► The enzyme showed a preferential specificity for ester of p-nitrophenyl acetate (C2).
► The enzyme exhibited Km of 4.2 mM and Vmax of 151 μmol min−1 mg−1 to C2 ester.
► The hydrolysis of fluorescence esters was increased in the presence of the enzyme.