Abstract
A new Staphylococcus xylosus strain was isolated. The extracellular lipase of S. xylosus (wt-SXL2) was purified to homogeneity from the culture medium. The specific activity of the purified enzyme, measured at pH 8.5 and 55 degrees C using tributyrin or olive oil emulsion, reached, respectively, 6300 U/mg or 2850 U/mg. The sequenced 18 N-terminal amino acid showed a high degree of identity with known staphylococcal lipase sequences.
The gene encoding the mature lipase was cloned and sequenced. The deduced amino acid sequence showed a significant similarity with various staphylococcal lipases. The highest overall identity (98.74%) was found with S. xylosus lipase (SXL1). The mature part of the lipase was expressed in Escherichia coli. The recombinant lipase was purified by affinity chromatography. The specific activity of the recombinant lipase was 4100 or 1500 U/mg using tributyrin or olive oil emulsion as substrate, respectively, at pH 8.5 and 55 degrees C.
The wild type and recombinant lipases presented a quite interesting thermal stability, after an incubation of 60 min at 55 degrees C and they are found to be highly stable at a pH ranging from 4 to 11. Due to its stability at high temperature and in organic solvent, the wt-SXL2 was used as biocatalyst to synthesise a high added value molecules. (C) 2011 Elsevier B.V. All rights reserved.