Determination and characterization of thermostable esterolytic activity from a novel thermophilic bacterium Anoxybacillus gonensis A4

A novel hot spring thermophile, Anoxybacillus gonensis A4 (A. gonensis A4) was investigated in terms of capability of tributyrin degradation and characterization of its thermostable esterase activity by the hydrolysis of p-nitrophenyl butyrate (PNPB). It was observed that A. gonensis A4 has an esterase with a molecular weight of 62 kDa. The extracellular crude preparation was characterized in terms of substrate specificity, pH and temperature optima and stability, kinetic parameters and inhibition/activation behaviour towards some chemicals and metal ions. Tributyrin agar assay showed that A. gonensis A4 secreted an esterase and V(max) and K(m) values of its activity were found to be 800 U/L and 176.5 microM, respectively in the presence of PNPB substrate. The optimum temperature and pH, for A. gonensis A4 esterase was 60-80 degrees C and 5.5, respectively. Although the enzyme activity was not significantly changed by incubating crude extract solution at 30-70 degrees C for 1 h, the enzyme activity was fully lost at 80 degrees C for same incubation period. The pH-stability profile showed that original crude esterase activity increased nearly 2-fold at pH 6.0. The effect of some chemicals on crude esterase activity indicated that A. gonensis A4 produce an esterase having serine residue in active site and -SH groups were essential for its activity.