Enhanced aqueous solubilization of tetrachloroethylene by a rhamnolipid biosurfactant

Clifford, Joseph; Ioannidis, Marios A.; Legge, Raymond L.

doi:10.1016/j.jcis.2006.10.026

Cited by 46 publications

(26 citation statements)

References 30 publications

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“…The lowest surface tension value reached by surfactin was recorded. The critical micelle concentration (CMC) of test surfactin was estimated from the intercept of two straight lines extrapolated from the concentration-dependent and concentration-independent sections of a curve plotted between surfactin concentration and surface tension values [17]. In parallel, the CMC of standard surfactin was determined and used for tentative estimation of the percentage purity of test surfactin [18,19] The emulsification index (E 24 ) was used to measure the emulsification activity of crude surfactin preparations (CFS and cell-containing culture broth containing 1.12 g/l surfactin) against different oil phases: hexadecane, linseed oil, kerosene, diesel (Solar), and motor oil (Pennzoil oil 10W-40) and carried out as mentioned before.…”

Section: Characterization Of the Produced Surfactinmentioning

confidence: 99%

Characterization of Surfactin Produced by Bacillus subtilis Isolate BS5

Abdel-Mawgoud

Aboulwafa

Hassouna

2008

Appl Biochem Biotechnol

129

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Physical and chromatographic characterization of the surfactin biosurfactant produced by Bacillus subtilis isolate BS5 has been conducted to study its potentiality for industrial application. The crude extract of test surfactin appeared as off-white to buff flake-like amorphous residue with bad odor similar to sour pomegranate. Test surfactin showed solubility in aqueous solution at pH>5 with optimum solubility at pH 8-8.5. It was also soluble in organic solvents like ethanol, acetone, methanol, butanol, chloroform, and dichloromethane. Surfactin crystals appeared rectangular with blunt corners and were arranged perpendicular to each other making a plus sign. Extracted surfactin showed high surface activity, as it could lower the surface tension of water from about 70 to 36 mN/m at approximately 15.6 mg/l. Moreover, test surfactin exhibited excellent stabilities at high temperatures (100 degrees C for up to 1 h at and autoclaving at 121 degrees C for 10 min), salinities (up to 6% NaCl), and over a wide range of pH (5-13). Test surfactin in the cell-free supernatant or crude culture broth forms showed high emulsification indices against kerosene (62.5% and 59%, respectively), diesel (62.5% and 66%, respectively), and motor oil (62% and 66%, respectively). These characters can effectively make test surfactin, in its crude forms, a potential candidate for the use in bioremediation of hydrocarbon-contaminated sites or in the petroleum industry. Chromatographic characterization of test surfactin, using high-performance liquid chromatography technique, revealed that the extracted surfactin contained numerous isoforms, of which six were found in the standard surfactin preparation (Fluka). Additional peaks appeared in the test surfactin and not in the standard one. These peaks may correspond to new surfactin isoforms that may be present in the test surfactin produced by B. subtilis isolate BS5.

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Section: Characterization Of the Produced Surfactinmentioning

confidence: 99%

Characterization of Surfactin Produced by Bacillus subtilis Isolate BS5

Abdel-Mawgoud

Aboulwafa

Hassouna

2008

Appl Biochem Biotechnol

129

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“…They observed a more significant drop of interfacial tension (i.e., 2-3 mN/m) in a PCE-TCE mixture obtained from the subsurface at the U.S. DOE Savannah River Site, due to precipitation of metal species at the interface between DNAPL and water forming a semi-rigid film at high DNAPL to water volume ratios. Clifford et al (2007) also showed that anionic biosurfactants (i.e., Rhamnolipids) can lower the interfacial tension of PCE from 45 to 10 mN/m, resulting in the increase in the solubility of PCE from 250 mg/L to 365 mg/L. Hence, results in this study show that the biological activity may not significantly affect the interfacial tension of CT mixtures due to the presence of surface active compounds in the mixtures.…”

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confidence: 58%

Influence of Wetting and Mass Transfer Properties of Organic Chemical Mixtures in Vadose Zone Materials on Groundwater Contamination by Nonaqueous Phase Liquids

Werth¹,

Valocchi²

2011

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Objectives:Previous studies have found that organic acids, organic bases, and detergent-like chemicals change surface wettability. The wastewater and NAPL mixtures discharged at the Hanford site contain such chemicals, and their proportions likely change over time due to reaction-facilitated aging. The specific objectives of this work were to 1) determine the effect of organic chemical mixtures on surface wettability, 2) determine the effect of organic chemical mixtures on CCl4 volatilization rates from NAPL, and 3) accurately determine the migration, entrapment, and volatilization of organic chemical mixtures. Tasks:Five tasks were proposed to achieve the project objectives. These are to 1) prepare representative batches of fresh and aged NAPL-wastewater mixtures, 2) to measure interfacial tension, contact angle, and capillary pressure-saturation profiles for the same mixtures, 3) to measure interphase mass transfer rates for the same mixtures using micromodels, 4) to measure multiphase flow and interphase mass transfer in large flow cell experiments, all using the same mixtures, and 5) to modify the multiphase flow simulator STOMP in order to account for updated P-S and interphase mass transfer relationships, and to simulate the impact of CCl4 in the vadoze zone on groundwater contamination.

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“…Organic acid anions exuded by roots may also enhance the desorption of hydrocarbons and/or compete for soil adsorption sites from the soil matrix, such as clay surfaces [6,255,266]. Moreover, some microorganisms are able to release biosurfactants, such as rhamnolipids, that can increase the solubility of certain organic contaminants and improve the ability of microbial cells to attach to oil droplets [267][268][269].…”

Section: Impact Of Root Exudates On Hydrocarbon Degradationmentioning

confidence: 99%

Root Exudation: The Ecological Driver of Hydrocarbon Rhizoremediation

2016

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Rhizoremediation is a bioremediation technique whereby microbial degradation of organic contaminants occurs in the rhizosphere. It is considered to be an effective and affordable "green technology" for remediating soils contaminated with petroleum hydrocarbons. Root exudation of a wide variety of compounds (organic, amino and fatty acids, carbohydrates, vitamins, nucleotides, phenolic compounds, polysaccharides and proteins) provide better nutrient uptake for the rhizosphere microbiome. It is thought to be one of the predominant drivers of microbial communities in the rhizosphere and is therefore a potential key factor behind enhanced hydrocarbon biodegradation. Many of the genes responsible for bacterial adaptation in contaminated soil and the plant rhizosphere are carried by conjugative plasmids and transferred among bacteria. Because root exudates can stimulate gene transfer, conjugation in the rhizosphere is higher than in bulk soil. A better understanding of these phenomena could thus inform the development of techniques to manipulate the rhizosphere microbiome in ways that improve hydrocarbon bioremediation.

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Enhanced aqueous solubilization of tetrachloroethylene by a rhamnolipid biosurfactant

Cited by 46 publications

References 30 publications

Characterization of Surfactin Produced by Bacillus subtilis Isolate BS5

Characterization of Surfactin Produced by Bacillus subtilis Isolate BS5

Influence of Wetting and Mass Transfer Properties of Organic Chemical Mixtures in Vadose Zone Materials on Groundwater Contamination by Nonaqueous Phase Liquids

Root Exudation: The Ecological Driver of Hydrocarbon Rhizoremediation

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