Purification and characterization of esterase from a thermophilic bacterium, Geobacillus sp. TF17

In this study, an esterase was purified from a thermophilic bacterium, Geobacillus sp. TF17, by using a Q-Sepharose ion exchange column and characterized. The purified enzyme was observed as a single band on native polyacrylamide gel electrophoresis. In the presence of pNPB as a substrate, the optimum temperature and pH of the enzyme were found to be 7.5 and 50 °C, respectively. The purified enzyme was extremely stable, in the range of pH 4.0-9.0, in the optimum pH value after 72 hour incubation at 4°C. When the thermal stability profile of the purified enzyme was analyzed, it was determined that the enzyme was extremely stable in the range of 30-50 °C after 72 h incubation. The Km and Vmax values of the purified enzyme were calculated as 0.056 mM and 19,38 U/mg protein, respectively, from the Lineweaver-Burk plot. The enzyme was inhibited more than about 60% of activity in the presence of some organic solvents such as isopropanol and acetonitrile. Additionally, it was detected that some metal ions affect the enzyme activity at different rates. As a result, Geobacillus sp. TF17 esterase had good pH and thermal stability. In addition this esterase has superior features than known in the literature in terms of Km, the Vmax values were shown to be compatible with the literature. Considering data obtained from this study, purified esterase has advantages for industrial or biotechnological applications in terms of especially its high thermal- and pH-stability.