Purification and characterization of lipase from a raw-milk yeast (Trichosporon asteroides)

A lipase-producing yeast strain was isolated from raw milk. It was identified as Trichosporon asteroides strain LP005. The lipase from this yeast was purified 8-fold to homogeneity for further characterization. The purification process for this lipase included (NH4)2SO4 precipitation at 70% saturation and gel filtration on Sephadex G-200. The molecular mass of the lipase was 37 kDa as determined by SDS/PAGE. The optimum pH and temperature for activity were pH 5.0 and 60 degrees C. The lipase was stable over a wide pH range (3.0-10.0) and at temperatures lower than 70 degrees C. The chelating agent EDTA did not affect activity of the enzyme, and this suggested that it was not a metalloenzyme. Treatment of tuna oil with T. asteroides LP005 lipase gave approx. 35 and 47% increases in the concentration of eicosapentaenoic acid and docosahexaenoic acid respectively. Thus, this lipase could potentially be used for the concentration step in the production process of such polyunsaturated fatty acids.