Purification and characterization of esterase from a thermophilic bacterium, Geobacillus sp. DF20

The esterase from a thermophilic bacterium, Geobacillus sp. DF20, was purified using Q-Sepharose ion exchange column and characterized. Native polyacrilamid gel electrophoresis stained by p-naphtyl acetate and Fast Blue B indicated the presence of two active esterase. Enzyme show highest activity in presence of p-nitrophenyl butirate (p-NPB) as a substrate at pH 7.0 and 50 ? C. The Km and Vmax values of the enzyme were calculated as 0.120 mM and 54.6 U/mg protein, respectively. The stability experiments of enzyme were carried out at +4 ? C, 50 ? C and 70 ? C. At the end of 5th hour, the enzyme lost the activity at 70 ? C. By the end of 72 hours, while the activity was protecting 100%, the activity had decreased at 50 ? C.When the enzyme incubated in buffer solution pH 5.0 and 7.0 at 4 ? C, the enzyme retained its original activity 70% and 50% respectively after 3 days. At 50 ? C, the enzyme activity lost its activity at pH 5.0 after 2 days incubation and conserved 95% its activity after 3 days. The effects of metal ions and some chemicals on the activity were also investigated.These data support that the esterase from Geobacillus sp. DF20 has some advantages for industrial or biotechnological applications.