Production and characterization of lipase from Bacillus stearothermophilus
The production of lipase by Bacillus stearothermophilus was investigated and its properties were evaluated. Different factors such as temperature, pH, carbon source, incubation period and culture volume were studied for improving lipase production. B. stearothermophilus was able to produce lipase at a wide range of temperature and pH values. The maximum enzyme activity of 90.569±0.068 U/ml was recorded when the microorganism was grown in a medium containing olive oil as a carbon source and supplied with Tween 80 at a temperature of 45°C and a pH of 8.0 for 24 h of fermentation. The enzyme showed good stability and tolerance for various parameters studied, with residual activity above 50% over a wide range of temperatures. Lipase was stable at pH 8.0 showing 99.64% of residual activity while it lost its stability almost completely at pH 6.0 and 10.0. The enzyme exhibited a moderate stability in organic solvents and seemed to be activated by isopropanol at a concentration of 25 and 100%. The enzyme retained more than 94% of its activity in a buffer system supplied with EDTA and retained over 80% of its activity in a buffer system supplied with Zn2+ compared to the metal ions investigated. These results show a great potential for the use of this enzyme in industry and other future studies.
Key words: Lipase, Bacillus stearothermophilus, optimization, enzyme characterization.