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.
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