Characterization of esterase activity in Geobacillus sp HBB-4

A thermophilic esterase producing bacterium (Bacillus sp. 4), recently isolated from Alangullu thermal spring in Aydin (Turkey), was analyzed using 16S rRNA and classified as Geobacillus sp. HBB-4, most closely related to Bacillus sp. BGSC W9A59 (0.70% sequence divergence) which belongs to the newly described genus Geobacillus. The effects of several chemicals on the activity of thermostable esterase from Geobacillus sp. HBB-4 were examined. Among the various metal ions tested, esterase activity was enhanced by Mn+2 and Ni+2, but was inhibited by Hg+2 and Cu+2, whereas Ca+2, Mg+2 and Co+2 had no effect. In addition, other metal ions studied have caused a slight inhibition on the esterase activity. EDTA partially inhibited the HBB-4 esterase. The activator metal ions, Mn+2 and Ni+2 have restored partial inhibition of EDTA. The activity of HBB-4 esterase was inhibited by ionic detergents while non-ionic detergents activated the enzyme. However, a zwitterionic detergent, CHAPS, has caused a slight inhibition in the enzyme activity. HBB-4 esterase activity was inhibited at the high concentrations of all the organic solvents tested in the present study. However, 50% final concentration of DMSO increased the enzyme activity about 7%. The HBB-4 esterase has shown more than about 50% of activity in the presence of ethanol and methanol solutions. These characteristics of the enzyme along with its significant thermostability make the Geobacillus sp. HBB-4 esterase a potent candidate for future industrial applications.