Properties of an extracellular lipase from a traditional yoghurt yeast
Purpose: To produce an organic solvent tolerant extracellular lipase from a traditional yoghurt Saccharomyces cerevisiae isolate and to characterize this enzyme activity. Material and Methods: A traditional yoghurt sample collected from a farm (Sivas-Turkey) was diluted and mixed with de Man, Rogosa and Sharp Medium (MRS) and poured into Petri dishes. One hundred colonies were selected and transferred onto MRS agar plates including Tween 80 as a lipase substrate. Only four colonies with lipase activity were incubated in MRS broth for 3 days at 37 degrees C and the extracellular proteins were precipitated with ethanol (95% v/v) from the supernatant. The precipitate with the highest lipase activity was selected for further analysis. Results: The optimum pH and temperature were 7.0 and 37 degrees C, respectively. While (1 mM) Mn2+ caused a slight increase (similar to 8%) Hg2+ or Zn2+ caused a substantial activity loss (similar to 70%). Organic solvents (5% chloroform or n-butanol, v/v) increased activity similar to 2.5 fold. Five percent SDS or Triton X-100 increased activity by 8% and 14%, respectively. The enzyme could hydrolyse hydroxyethyl methacrylate (HEMA) and 2,3-epoxy propyl methacrylate (GMA), retained similar to 83% of its activity after 1 hour at 37 degrees C, lost no activity when stored at pH 7.0 and at 4 degree C for 60 days. Conclusion: The properties of the extracellular yeast lipase was investigated using a number of physiological parameters. The results obtained indicated that it was an organic solvent-and detergent tolerant enzyme having the optimum activity at mild reaction conditions.