Rhamnolipid from a Lysinibacillus sphaericus strain IITR51 and its potential application for dissolution of hydrophobic pesticides

Rhamnolipid produced from a Lysinibacillus sphaericus IITR51 was characterized and its ability for dissolution of hydrophobic pesticides were evaluated. L. sphaericus produced 1.6 g/L of an anionic biosurfactant that reduced surface tension from 72 N/m to 52 N/m with 48% emulsification index. The biosurfactant was found stable over a wide range of pH (4.0-10.0), temperature (4-100 degrees C), salt concentration (2-14%) and was identified as rhamnolipid. At the concentration of 90 mg/L rhamnolipid showed enhanced dissolution of alpha-, beta-endosulfan, and gamma-hexachlorocyclohexane up to 7.2, 2.9, and 1.8 folds, respectively. The bacterium utilized benzoic acid, chlorobenzene, 3- and 4-chlorobenzoic acid as sole source of carbon and was found resistant to arsenic, lead and cadmium. Furthermore, the isolated biosurfactant showed antimicrobial activities against different pathogenic bacteria. The results obtained indicate the usefulness of rhamnolipid for enhanced dissolution and thereby increasing the bioavailability.