Characterization of a New Thermostable Carboxylesterase from Aneurinibacillus sp. PDF24

In this study, esterase of Aneurinibacillus sp. PDF24 strain, a thermophilic bacteria, was purified to homogenity (5.25 fold purification) by column chromotography, and characterized. The molecular weight of Aneurinibacillus sp. PDF24 esterase was determined about 40 kDa. The maximum activity of the purified esterase was analyzed at 55°C, pH 8.5. The esterase was found to be stable at 40ºC, 50ºC and 60ºC for 1 hour. Km and Vmax values for p-nitrophenyl butyrate were determined as 0.120 mM and 3164.8 U/mg, respectively. Considering Km values in the literature, Aneurinibacillus sp. PDF24 esterase was found to have a good Km value compared to other esterases. In the presence of 1 mM and 5 mM metal salts of Mg2+, Li+, Ca2+, K+, no significant change occured in enzyme activity. The activity of Aneurinibacillus sp PDF24 esterase was found to be stable also in the presence of ethanol, DMSO, EDTA, DTT and ß-mercaptoethanol. The data obtained suggest that the enzyme is a serine esterase, not a metalloprotein, and that disulfide bonds are not required to maintain enzyme conformation, and therefore, depending on its features, this esterase may be a suitable candidate for industrial applications.