Surfactants rhamnolipid

Zhang, Y. Miller, R. M. (1992). Enhanced octadecane dispersion and biodegradation by a Pseudomonas rhamnolipid surfactant (biosurfactant). Applied and Environmental Microbiology, 58, 3276-82. 

Gruber, T., Chmiel, H., Kappeli, O., Sticher, P., Fiechter, A. (1993). Integrated process for continuous rhamnolipid biosynthesis. In N. Kosaric (Eds.) Biosurfactants (surfactants science series) (vol. 48, (pp. 157-173)). New York Marcel Dekker. 

Rhamnolipid Biosurfactant A Natural, Low-Toxicity Alternative to Synthetic Surfactants... 

Similarly, naturally derived surfactants extracted from fermentation broths or prepared by partial hydrolysis of natural extracts can contain polysaccharides, proteins, and phospholipids. For example, rhamnolipids and sophorolipids have unique structural features that cause them to deposit on chemically similar surfaces and modify surface energy even at very low concentrations. Clearly, the emergence of biotechnology in the twenty-first century will drive the development of new surfactants from microbial fermentation, and improve the commercial viability of known surfactants from such processes. 

Mata-Sandoval et al. [32] compared the ability of the rhamnolipid mixture to solubilize the pesticides, trifluralin, coumaphos and atrazine, with the synthetic surfactant Triton X-100. The synthetic surfactant was able to solubihze approximately twice as much of all pesticides as the rhamnolipid. The biosurfactant seems to bind trifluralin tightly in the micelle and releases the pesticide slowly to the aqueous phase, which could have implications for microbial uptake. This approach utilizing micellar solubilization capacities and aqueous-miceUe solubilization rate coefficients and micellar-aqueous transfer rate coefficients could be useful for future studies on microbial uptake. Addition of rhamnohpid in the presence of cadmium enabled biodegradation of the hydrocarbon naphthalene to occur as if no cadmium was present [33]. 

A review by Maier and Soberon-Chavez [ 19] showed that hexadecane, tetradecane, pristine, creosote and hydrocarbon mixture in soils. Other researchers [35] compared the solubilization of naphthalene by a rhamnolipid, sodium dodecyl sulphate (SDS), an anionic surfactant and Triton X-100, a non-ionic surfactant. The biosurfactant increased the solubility of naphthalene by 30 times. However, biodegradation of naphthalene (30mg/L) took 40 days in the presence of biosurfactant (lOg/L) compared with lOOh for an equal concentration of Triton X-100 (10 g/L). It appeared that the biosurfactant was used as a carbon source instead of the naphthalene which did... 

Rhamnolipids from the UG2 strain were able to enhance the solubilization of four-ring PAHs in a bioslurry more significantly than three-ring PAHs and that the biosurfactants were live times more effective than SDS [36], However, high molecular weight PAHs were not biodegraded despite surfactant addition. Providenti et al. [37] also studied the effect of UG2 biosurfactants on phenanthrene mineralization in soil slurries and showed that lag times decreased and degradation increased. 

Besides studies on biodegradation, rhamnolipid surfactants have been tested to enhance the release of low solubility compounds from soil and other solids. They have been found to release three times as much oil as water alone from the beaches in Alaska after the Exxon Valdez tanker spiU [40]. Removal efficiency varied according to contact time and biosurfactant concentration. Scheibenbogen et al. [41] found that the rhamnolipids from R aeruginosa UG2 were able to effectively remove a hydrocarbon mixture from a sandy... 

Various biological surfactants were compared by Urum et al. [53] for their ability to wash a crude oil-contaminated sod. They included rhamnolipid, aescin, lecithin, saponin, tannin and SDS. Temperature (5,20,35 and 50°C), surfactant concentration (0.004,0.02,0.1 and 0.5%), surfactant volume (5,10, 15 and 20 ml), shaker speed (80,120,160 and 200 strokes/min) and wash time (5, 10, 15 and 20 min) were evaluated. The conditions of 50°C and 10 min were optimal for most of the surfactants such as the rhamnohpid, SDS and saponin were able to remove more than 79% of the oil. 

Mulligan [61] determined that the rhamnolipid ratio to metal ratio was —3 1 in soil washing experiments with 0.01% but this ratio increased substantially as the concentration of surfactant increased. Solubilization in the micelle was also examined using the following equation ... 

From Table 2, it can be seen that for the rhamnolipid at lower biosurfactant concentrations, the ratio of metal in the micelle to that in the aqueous phase is lower. Concentrations of 1% rhamnolipid unfortunately made it difficult to determine the due to emulsification. Metals appeared to have higher affinities at low surfactant concentrations which agrees with solubilization trends. This also explains why multiple washes at low concentrations are successful. 

Attempts are being made to determine non-aqueous phase liquid (NAPL) mole fraction and micelle-aqueous partition coefficients with rhamnolipids to understand equilibrium solubilization behaviour in surfactant-enhanced soil remediation situations [51]. A modification of Raoult s law was used for surfactant-enhanced solubilization but deviation from this ideal behaviour depended on the hydrophobicity of the compounds and the NAPL-phase mole fraction. Micelle-water partition coefficients were non-Unear in relation to the NAPL-phase mole fraction. Also enhancements by the surfactant were... 

Metal removal from a sandy soil contaminated with 1710 mg/kg of Cd and 2010 mg/kg of Ni was later evaluated [3]. Maximum removal was obtained by foam produced by 0.5% rhamnolipid solution, after 20 pore volumes. Removal efficiency for the biosurfactant foam was 73.2% of Cd and 68.1% of Ni. For the biosurfactant liquid solution, 61.7% Cd and 51.0% Ni were removed. This was superior to Triton X-100 foam which removed 64.7% Cd and 57.3% Ni and liquid Triton X-100 which removed 52.8% Cd and 45.2% Ni. Distilled water removed only 18% of both Cd and Ni. Concentrations of 0.5,1.0 and 1.5% rhamnohpid at pH values of 6.8,8 and 10 were also evaluated but did not show significant effects. For a 90% foam quaUty, the average hydraulic conductivity was 4.1 X 10 cm/s, for 95%, it was 1.5 X 10 cm/s and for 99%, it was 2.9 X 10 cm/s. Increasing foam quality decreases substantially the hydraulic conductivity. All these values are lower than the conductivity of water at 0.02 cm/s. This higher viscosity will allow better control of the surfactant mobihty during in situ use. Therefore, rhamnohpid foam may be an effective and non-toxic method of remediating heavy metal, hydrocarbon... 

Davey ME, Caiazza NC, O Toole GA. Rhamnolipid surfactant production affects biofilm architecture... 

Other studies [85] have shown that cationic bacitracin, anionic AOT, and nonionic Tween 80 all enhanced cellulose hydrolysis, implying that the charge of the surfactant was not an important consideration. In fact. Tween 80 (0.1%) increased the rate and extent of saccharification by up to 40% [82,85]. The structure of the hydrophilic head group of the surfactant also had little significance [85], Those with a sugar group, sophorolipid and rhamnolipid, worked well, as did bacitracin, which has a peptide hydrophilic group [85]. 

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