Production and characterization of alkaline extracellular lipase from newly isolated strain Aspergillus awamori HB-03

Abstract

A strain HB-03 to produce alkaline extracellular lipase was isolated from oil-rich soil samples and identified as Aspergillus awamori. The growth conditions and nutritional factors for lipase production by strain HB-03 were optimized, and the maximum lipase production of (45.9±2.3) U/mL was obtained at 30 ℃ and pH 7.0 after 36 h using olive oil (1％) and sucrose (0.5％) as carbon sources and combination of peptone (2％), yeast extract (0.5％) and ammonium sulfate (0.1％) as nitrogen sources. The lipase was purified to homogeneity with 10.6-fold, 18.84％ yield and a specific activity of I 862.2 U/mg using ammonium sulfate precipitation followed by SephadexG-75 gel filtration chromatography. The purified lipase with molecular mass of 68 ku was estimated by SDS-PAGE. The optimum pH and temperature for the purified lipase were found to be 8.5 and 40 ℃, respectively. The lipase kept more than 80％ of activity in pH 7.0-10.0 and temperatures up to 45 ℃.The metal ions of Mn(superscript 2+), Ba(superscript 2+) significantly enhanced the lipase activity, whereas Cu(superscript 2+), Fe(superscript 3+) and Mg(superscript 2+) strongly reduced the lipase activity. The K(subscript m) and V(subscript max) values of the purified enzyme for p-nitrophenyl palmitate were 0.13 mmol/L and 60.6 mmol/(L‧min), respectively. The results show that this novel lipase has potential industrial applications.