Optimization and Partial Purification of an Extracellular Esterase Produced by a Bacillus safensis Strain Isolated from Ear Wax

Abstract

The esterases catalyzing the hydrolysis of acyl esters are highly desired in industrial applications. An extracellular esterase producing, mesophilic and alkaliphilic Gram positive bacterial isolate obtained from human ear wax (sebum) was identified as Bacillus safensis strain. The B. safensis strain produced relatively higher amount of esterase after 36 h at 37o C under shaking conditions when coconut oil (1.75 %, v/ v) and gelatin (0.6 %, w/v) were used in the Mineral-Based broth as carbon and nitrogen source, respectively. The esterase production by B. safensis strain increased by ~208 % by consecutive optimization of physicochemical parameters. The esterase was partially purified by acetone precipitation. Enzyme showed greater affinity towards a relatively short C-chain ester p-NPA as substrate. The Km and Vmax values of the esterase were found to be 0.127 mM and 8.82 U/ml/min, respectively. The esterase was purified up to 2.8 fold by acetone precipitation (20-40 % saturation). The esterase was found to be a heptameric protein of 49 kDa (under native-PAGE) comprising seven units of 4 7 kDa as revealed by SDS-PAGE.