Extracellular lipase of Aspergillus niger NRRL3; production, partial purification and properties

Four strains of Aspergillus niger were screened for lipase production. Each was cultivated on four different media differing in their contents of mineral components and sources of carbon and nitrogen. Aspergillus niger NRRL3 produced maximal activity (325U/ml) when grown in 3% peptone, 0.05% MgSO4.7H(2)O, 0.05% KCl, 0.2% K2HPO4 and 1% olive oil:glucose (0.5:0.5). A. niger NRRL3 lipase was partially purified by ammonium sulphate precipitation. The majority of lipase activity (48%) was located in fraction IV precipitated at 50-60% of saturation with a 18-fold enzyme purification. The optimal pH of the partial purified lipase preparation for the hydrolysis of emulsified olive oil was 7.2 and the optimum temperature was 60A degrees C. At 70A degrees C, the enzyme retained more than 90% of its activity. Enzyme activity was inhibited by Hg2+ and K+, whereas Ca2+ and Mn2+ greatly stimulated its activity. Additionally, the formed lipase was stored for one month without any loss in the activity.