Screening and isolation of potent biosurfactant producing Bacillus subtilis CS14 from contaminated soil samples of Kanchipuram, India

A good biosurfactant must reduce the surface tension of the water from 72 to 35 milli-Neuton/meter (mN/m) and should show a surface activity of at least 37 mN/m. An extensive screening with 13 contaminated soils and one oil refinery sludge was carried out to isolate a potential strain.. Totally 3662 colonies were obtained from all 14 contaminated soil samples over a period of three months from which 212 morphologically different colonies were tested for biosurfactant production and 22 positive strains were identified. All the isolates were tested quantitatively and the isolate CS14 showed maximum surface activity of 51.38 mN/m. Taxonomic identification of the biosurfactant producing strain CS14 was performed using 16s rDNA studies and was identified as Bacillus subtilis.