English

Abstract

In this study, a wild (LPF-5) and a mutant (HN1) strain of A. niger were compared for lipase production. Several physical parameters (carbon source, nitrogen source, pH, temperature and incubation period) were optimized for maximization of lipase production. Lipase activity between wild type and mutant strain were compared. Among all carbon sources, mixture of glucose (1%, w/v) and olive oil (1%, v/v) exhibited maximum increase in the production of lipases by both the wild (94.91 ± 0.60 U mL-1 min-1) and mutant (118.23 ± 0.73 U mL-1 min-1) strain. Addition of glucose into the production medium (containing olive oil) increased the production of lipase up to 20% in case of both the strains. The production of lipase by both the strains was higher in the medium of pH 7.0 containing peptone (1%, w/v) as nitrogen source after 3 days of incubation at 28°C. The activity of lipase from HN1 strain in optimized medium was 40% higher (147.65 ± 1.14 U mL-1 min-1) than in un-optimized medium (105.19 ± 0.91 U mL-1 min-1), while it was 38% higher for LPF-5 strain in optimized medium. Therefore, the mutant strain (A. niger HN1) is prospective for the development of industrial biotechnology for production of extracellular lipase. Lipase enzyme was partially purified by ammonium sulfate precipitation and 70% precipitate showed highest specific activity of 66.12 U mg-1 for mutant strain as compared to specific activity of 29.88 U mg-1 in crude lysate.   Key words: Wild strain, mutant strain, Aspergillus niger, lipase activity, specific activity, ammonium sulfate.