Purification and biochemical characterization of an extracellular lipase from psychrotolerant Pseudomonas fluorescens KE38

An extracellular lipase producing bacterium was isolated from a soil sample, and identified as a strain of Pseudomonas fluorescens by 16S rRNA gene sequencing. It was named Pseudomonas fluorescens KE38. KE38 showed psychrotolerant properties with an optimum growth temperature of 25 degrees C. The lipase enzyme secreted by KE38 was purified 41.13-fold with an overall yield of 54.99%, and a specific activity of 337.3 U/mg. The molecular mass of purified lipase was estimated to be approximately 43 kDa by SDS-PAGE. Although the lipase was active at a temperature range of 15-65 degrees C, it exhibited maximum activity at 45 degrees C, at pH 8.0. The enzyme exhibited high stability retaining 100% and 70% of its activity after an incubation period of 45 and 100 min. at 45 degrees C and pH 8.0 respectively. It also showed a broad substrate specificity acting on p-nitrophenyl esters with C-8-C-18 acyl groups as substrates and was activated by Ca2+ and Ni2+ at 1 mM. While the enzyme retained its activity levels in the presence of a variety of organic solvents, DMSO and dimethylformamide enhanced this. High stability, broad substrate specificity and activity at cold temperatures in the presence of organic solvents, and metal ions make the extracellular lipase of KE38 a candidate for industrial applications.