Investigation of lipase/esterase capabilities of a novel bacteriım, Anoxybacillus gonensis A4

SUMMARY Investigation of Esterase Capabilities of a Novel Bacterium, Anoxybacillus gonensis A4 In this study, esterolytic activities of a novel thermophilic bacterium, Anoxybacillus gonensis A4 strain, were investigated. Occurence of an extracellular enzyme that hydrolyzes ester bonds was dedected by tributyrin agar assay. Formation of clear zones around A. gonensis A4 isolates on agar plates containing tributyrin also supported the presence of an esterase in this thermophile. 0.3% Carboxymethylcellulose stimulated both the growth in Luria-Bertani (LB) medium and the esterase activities determined spectrophotometrically using /7-nitrophenylbutyrate as substrate. The extracellular crude enzyme prepared from A. gonensis cultures showed greater substrate specicifities for short chain /7-nitrophenylesters than those for long chain /7-nitrophenylesters. The temperature optimum of A. gonensis A4 extracellular esterase was found to be nearly 80 °C and its pH optimum was dedected to be 5.5. When thermostability data was examined, it was seen that the esterolytic activity was stimulated at about 20% levels at temperatures ranging from 30 to 70 °C after 30 minutes of incubation. The effectiveness of various metal ions on the enzyme activity was tested for chloride salts of 1 1 metal ions at final concentration of 1 mM. In the presence of K+, the activity was enhanced at about 15%. The other ions had either no effect on esterase activities or possessed different inhibition profiles. Inhibition by phenylmethylsulphonylfluoride supported the presence of a critical serine residue thought to be significant for catalytic activity. All these results support that Anoxybacillus gonensis A4 strain excretes a highly thermostable true esterase possesing interesting characteristics some of which are similar to esterases reported earlier. Key Words: Thermophilic, Thermostable, Anoxybacillus, Lipase, Esterase VI