Abstract

A newly moderate halophilic strain LY7-8 with high lipolytic activity was isolated from salt lake of Yuncheng, China. Biochemical and physiological characterization, along with 16S rRNA sequence analysis placed the isolate in the genus Chromohalobacter. Lipase production started from the early-exponential phase of bacterial growth and reached a maximum level during the mid-stationary phase. The enzyme was highly active against p-nitrophenyl esters with acyl chain lengths of C8 to C18, indicating a lipase activity. Enzyme purification was carried out by ammonium sulphate precipitation and Sephacryl S-100 gel filtration chromatography. Molecular weight of the lipase was determined to be 44 kDa on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The purified enzyme was highly active over broad temperature (30 to 90°C), pH (6.0-12.0) and NaCl concentration (0 to 20%) ranges, showing optimal activity at 60°C, pH 9.0 and 12.5% NaCl. Significant inhibition of the lipase was shown by ethylenediaminetetraacetic acid (EDTA), phenylmethylsulfonyl fluoride (PMSF) and diethyl pyrocarbonate (DEPC), indicating it was a metalloenzyme with serine and histidine residues essential for its catalytic function. Moreover, it exhibited high activity in the presence of surfactants, such as SDS and Triton X-100. Results from the present study indicated that the extracellular lipase from LY7-8 may have considerable potential for industrial application from the perspectives of its properties.

Key words: Moderately halophile, lipase, purification, Chromohalobacter