Adsorption of a Multicomponent Rhamnolipid Surfactant to Soil

Abstract

The adsorption of rhamnolipid, a multicomponent biosurfactant with potential application in soil remediation, to two sandy soils was investigated using batch and column studies. The surfactant mixture contained six anionic components differing in lipid chain length and number of rhamnose moieties. Batch adsorption experiments indicated that the overall adsorption isotherms of total surfactant and of the individual components leveled off above a concentration at which micelles were formed. Column experiments showed that the retardation factors for the total surfactant and for the individual components decreased with increasing influent concentration. Extended tailing was observed in the distal portion of the surfactant breakthrough curve. The concentration-dependent retardation factors and the extended tailing are in accordance with the nonlinear (concave) adsorption isotherms found in the batch adsorption studies. The more hydrophobic rhamnolipid components were preferentially adsorbed, but adsorption was not correlated with the organic carbon content of the soil. This suggests that adsorption of rhamnolipid to soil is not a partitioning process but mainly an interfacial adsorption process.

Enhanced bioremediation of n-alkane in petroleum sludge using bacterial consortium amended with rhamnolipid and micronutrients

“…In a study by Oberbremer and MullerHurtig (1989), a positive correlation has been obtained between reduction in surface tension of the fluid phase in a stirred soil bioreactor and the onset of biodegradation of hydrophobic petroleum hydrocarbons. It has also been previously reported about the rhamnolipid biosurfactant mediated reduction in surface tension (Banat et al, 2000;Noordman et al, 2000).…”

Rhamnolipid Stimulates Uptake of Hydrophobic Compounds by Pseudomonas aeruginosa

“…Rhamnolipid was produced by P. aeruginosa UG2 during growth with glucose (28,34) and was isolated from the culture supernatant by a series of consecutive steps of acid precipitation and dissolution in 50 mM NaHCO 3 . It was purified by column chromatography over Sephadex LH20 with methanol as the eluent (28).…”

“…Rhamnolipid was produced by P. aeruginosa UG2 during growth with glucose (28,34) and was isolated from the culture supernatant by a series of consecutive steps of acid precipitation and dissolution in 50 mM NaHCO 3 . It was purified by column chromatography over Sephadex LH20 with methanol as the eluent (28). Emulsan, the lipo-heteropolysaccharide bioemulsifier produced by A. calcoaceticus RAG1, was isolated from a culture grown with ethanol by ammonium sulfate precipitation, dialysis, and washing with diethylether (33).…”

The enhancement by surfactants of hexadecane degradation by Pseudomonas aeruginosa varies with substrate availability

“…Rhamnolipid was produced by P. aeruginosa UG2 during growth on glucose in a mineral salts medium ( Van-Dyke et al, 1993), isolated from the culture broth by a series of consecutive steps of acid precipitation and dissolution in 50 mM NaHCO 3 , and purified by column chromatography over Sephadex LH20 with methanol as the eluent (Noordman et al, 2000a).…”

“…Splitless injection with a 1 min pressure ramp of 250 kPa was used for analyzing samples with a low hexadecane concentration. Rhamnolipid was analyzed by HPLC using evaporative light scattering detection (ELSD) (Noordman et al, 2000a). SDBS was analyzed by HPLC using UV detection at 228 nm (Noordman et al, 2000b).…”