title: Production and physico-chemical characterization of a biosurfactant produced by Pseudomonas aeruginosa OBP1 isolated from petroleum sludge.
abstract: Pseudomonas aeruginosa strain OBP1, isolated from petroleum sludge, was used to produce biosurfactant from a modified mineral salt medium with 2% n-hexadecane as sole source of carbon. The crude biosurfactant was fractionated using TLC and HPLC. Using FTIR spectroscopy, ¹H NMR, and LC-MS analyses, the chemical structure of the purified fraction of crude biosurfactant was identified as rhamnolipid species. The LC-MS spectra show that monorhamnolipid (L-rhamnopyranosyl-β-hydroxydecanoyl-β- hydroxydecanoate, Rha-C₁₀-C₁₀) was produced in abundance with the predominant congener [M-H]⁻ ions for L-rhamnopyranosyl-L-rhamnopyranosyl-3-hydroxydecanoyl-3-hydroxydecanoate (Rha-Rha-C₁₀-C₁₀). Seven different carbon substrates and five nitrogen sources were examined for their effect on rhamnolipid production. Using n-hexadecane (20 g/l) as carbon substrate and urea along with (NH₄)₂SO₄ (2 g/l each) as nitrogen source was found to be the best, with a maximum yield of 4.8 g/l. The biosurfactant reduced the surface tension of water to 31.1 mN m⁻¹ with a critical micelle concentration of 45 mg/l. The biosurfactant showed a better emulsifying activity against a variety of hydrocarbon and achieved a maximum emulsion index of 82% for diesel. The purified biosurfactant showed a significant antibacterial activity against Staphylococcus aureus at a minimum inhibitory concentration of 8 μg/ml.
authors.affiliation: Department of Molecular Biology & Biotechnology, Tezpur University, Napaam, Tezpur, Assam 784028, India. prangen@tezu.ernet.in
authors.forename: Pranjal
authors.initials: P
authors.lastname: Bharali
authors.forename: Bolin Kumar
authors.initials: BK
authors.lastname: Konwar
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology; D002244:Carbon; D002851:Chromatography, High Pressure Liquid; D003651:Decanoates / Q000737:chemistry; D045703:Emulsifying Agents / Q000737:chemistry / Q000494:pharmacology; D006017:Glycolipids / Q000737:chemistry* / Q000494:pharmacology*; D009682:Magnetic Resonance Spectroscopy; D008823:Micelles; D008826:Microbial Sensitivity Tests; D015394:Molecular Structure; D009584:Nitrogen; D010578:Petroleum / Q000382:microbiology; D011550:Pseudomonas aeruginosa; D012210:Rhamnose / Q000031:analogs & derivatives / Q000737:chemistry; D012722:Sewage / Q000382:microbiology; D017550:Spectroscopy, Fourier Transform Infrared; D013211:Staphylococcus aureus / Q000187:drug effects; D013500:Surface Tension; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D000900:Anti-Bacterial Agents; D003651:Decanoates; D045703:Emulsifying Agents; D006017:Glycolipids; D008823:Micelles; D010578:Petroleum; D012722:Sewage; D013501:Surface-Active Agents; C418382:rhamnolipid; C085734:rhamnopyranosyl-3-hydroxydecanoyl-3-hydroxydecanoate; D002244:Carbon; D009584:Nitrogen; D012210:Rhamnose