Relationship between Micellar and Hemi-Micellar Processes and the Bioavailability of Surfactant-Solubilized Hydrophobic Organic Compounds

Abstract

In a landmark study on surfactant-enhanced biodegradation of hydrophobic organic compounds (HOCs), Guha and Jaffé demonstrated that a fraction (f) of micellar-phase HOC is directly bioavailable to bacterial cells. They developed a theoretical description of fwhich provided an excellent model of the experimental results. However, a mass transfer term describing the transport of the HOC through the cell wall (m(c)) was found to vary over an order of magnitude for the different surfactants examined, and a theoretical description of it remained elusive. This elusivity also resulted in the model not being able to describe a priori why fwas zero for the non-ionic surfactant C12E23. Here, the results of a recent study on surfactant sorption are used to develop an alternative mechanism describing m(c), where hemi-micellar formation on the cell surface is incorporated into the pathway describing micellar HOC bioavailability. The revised model is validated against HOC bioavailability data for five different C12E(y) surfactants, and it is shown that a single value for the mass transfer coefficient describing transfer of the hemi-micellar HOC into the bacterial cell is able to replicate the complete C12E(y) dataset, including that of C12E23 which eluded the original model. Overall, the results indicate that surfactant sorption and hemi-micelle formation are important parameters governing surfactant-enhanced bioavailability.

Effects of dissolved organic matter derived from forest leaf litter on biodegradation of phenanthrene in aqueous phase

“…On the other hand, the strain phe-1 could use the bound phenanthrene directly. For example, HA (a form of DOM ) which has been described with a micellar microstructure similar to that of surfactants, can incorporate dissolved PAHs [12], and a fraction of micellar-phase PAHs is directly bioavailable to cells and does not need to be dissolved in the liquid phase [59]. DOM with many hydrophobic and nonpolar components may be more effective for biodegradation of PAHs because degrading bacteria can access to the incorporated DOM-PAHs directly, and the bioavailability of DOM-PAHs is higher than that of dissolved PAHs [2,22,32].…”

Biosurfactants are useful tools for the bioremediation of contaminated soil: a review

“…Brown (2007) explains the apparent aqueous solubility of the contaminant as the sum of the aqueous (C aq ) and micellar (C mic ) HOC concentrations. Edwards et al, (1991) established that micellar-phase HOC concentration can be modeled using a linear partition relationship of the form:…”

Effect of Glucopon 215 on cell surface properties of Pseudomonas stutzeri and diesel oil biodegradation

“…A fraction of the phenanthrene partitioned into the micellar phase of some nonionic surfactants can be directly bioavailable to phenanthrene-degrading microorganisms. Moreover, Brown (2007) described that hemi-micelle formation on the bacterial cell surface is a necessary requirement for surfactant-enhanced biodegradation of hydrophobic organic compounds. What is more, the nonionic surfactant Brij 30 forms hemi-micelles on the bacterial cell surface and phenanthrene sorption at the bacterial surface is enhanced by the surfactant (Lanzon and Brown, 2013).…”