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 °C 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 1 862.2 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 °C, respectively. The lipase kept more than 80% of activity in pH 7.0–10.0 and temperatures up to 45 °C. The metal ions of Mn²⁺, Ba²⁺ significantly enhanced the lipase activity, whereas Cu²⁺, Fe³⁺ and Mg²⁺ strongly reduced the lipase activity. The K_m and V_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.

Keywords

alkaline lipase / Aspergillus awamori / purification / characterization