Enhanced Production of Extracellular Alkaline Lipase by an Improved Strain of Pseudomonas aeruginosa MTCC 10,055

Abstract

Problem statement: Lipases are industrially important enzymes having applications in numerous industries. For easy commercialization it is necessary to produce lipases at industrial level which could be achieved by strain improvement and medium formulation. Approach: In the present study strain improvement of Pseudomonas aeruginosa MTCC 10,055 was done by chemical mutagenesis using mutagen 4-nitroquinoline1-oxide for alkaline lipase production. Different fermentation parameters affecting lipase production were optimized using one-variable-at-a-time approach. Results: The selected mutant (M-05) exhibited 3.6-fold higher productivity over wild type. Maximum alkaline lipase was produced when culture was incubated at 35°C with initial medium pH 9.0 in 28 h with inoculum density 0.5% (v/v) (Abs₆₁₀-1.0). Supplementation of production medium with combination of castor oil and starch as carbon source and Triton-X-100 as surfactant significantly influenced the alkaline lipase production. The composition of fully optimized medium was determined to be (g L^-1): (NH₄)₂SO₄, 1.0; KH₂PO₄, 0.6; MgSO₄, 0.4; yeast extract, 0.2; castor oil, 2.0; starch 20.0; gum arabic, 5.0; Triton-X-100, 1.0. An overall 14-fold enhanced production was achieved after complete medium optimization. Conclusion/Recommendations: The improved strain was capable to produce high titer of alkaline lipase at flask level, which can be examined at fermentor level to obtain sufficient enzyme yield to meet the world wide industrial demand.