Expression, purification of a novel alkaline Staphylococcus xylosus lipase acting at high temperature

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 °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 °C. The wild type and recombinant lipases presented a quite interesting thermal stability, after an incubation of 60 min at 55 °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.