Optimization of fermentation culture conditions for Alkaline Lipase Production by Bacillus flexus XJU-1

Studies were carried out for optimizing extracellular alkaline lipase production by Bacillus flexus XJU-1 under submerged fermentation. Maximum alkaline lipase activity was observed at 36 h when 2% (v/v) refined cotton seed oil was used as a sole carbon source at an initial pH 11.0 at 37°C with 2% inoculum (v/v), 1.5% (w/v) yeast extract as nitrogen source and 0.5% (v/v) Tween 80 as a surfactant. An overall 6.47-fold increase in alkaline lipase activity (from 2.83 U/ml to 18.31 U/ml) was achieved after optimizing the various nutritional and physicochemical parameters. The extracellular alkaline lipase was purified to homogeneity in a two-step procedure involving acetone precipitation and anion exchange chromatography. A specific activity of 312.4 U/mg with 40.1% recovery in enzyme activity in comparison to crude enzyme extract was recorded. The purified alkaline lipase was homogeneous as shown by a single band on SDS-PAGE with an apparent molecular weight of 16.1 kDa. The production of higher amount of lipase under strong alkaline conditions using a cheap oil substrate makes this strain a good candidate for detergent and leather industries.