Screening and optimization of media constituents for enhancing lipolytic activity by a soil microorganism using statistically designed experiments.

Soil contaminated with vegetable cooking oil was used in the isolation of a lipase-producing microorganism. The effectiveness of two different statistical design techniques in the screening and optimization of media constituents for enhancing the lipolytic activity of the soil microorganism was determined. The media constituents for lipase production by the isolated soil microorganism were screened using a Plackett-Burman design. Oil, magnesium sulfate, and ferrous sulfate were found to influence lipolytic activity at 24 and 72 h of culture with very high confidence levels. Whereas oil and ferrous sulfate showed a positive effect, magnesium sulfate indicated a negative effect on the lipolytic activity. A central composite design (CCD) followed by response surface methodology was used in optimizing these media constituents for enhancing the lipolytic activity. The regression model obtained for 72 h of lipolytic activity was found to be the best fit, with R 2=0.97, compared with the other model. An optimum combination at 9.3 mL/L of oil, 0.311 g/L of magnesium sulfate, and 0.007 g/L of ferrous sulfate in the media gave a maximum measured lipolytic activity of 7.1 U/mL at 72 h of culture. This increase in lipolytic activity was found to be 10.25% higher than the maximum experimentally observed value in the CCD.