Optimization of critical growth parameters for enhancing extracellular lipase production by alkalophilic Bacillus sp.

Lipase producing bacterial strains were isolated from oil contaminated soil samples. These bacterial strains were screened qualitatively and quantitatively for lipase production. The alkalophilic bacterial strain (Bacillus sp. KS4) possessing maximum extracellular lipase activity (0.612 U/ml) was selected. Further optimization studies for enhancing lipase production were performed using statistical approach. For maximal lipase production by the selected strain, various culture medium parameters such as incubation temperature, pH, carbon source, nitrogen source, surfactant and metal ion were first screened using “one-variable-at-a-time” approach. The concentration of four selected critical medium parameters viz. carbon source (olive oil), surfactant (tween 80), metal ion (MgCl2) and inoculum size which were found to have the most significant effect on lipase production was further optimized employing response surface methodology for enhancing lipase production. The maximum lipase production was achieved with 1.16% olive oil, 0.12% tween 80, 5.99 mM MgCl2, and 7.16% inoculum size. Verification experiment confirmed the validity of the model and accuracy of the predicted results. The optimization of production medium led to an increase in enzyme activity from 0.612 U/ml to 2.17 U/ml showing a 3.54 fold increase in lipase production.