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Preferential surfactant utilization by a PAH-degrading strain: effects on micellar solubilization phenomena
1Environmental and Water Resources Engineering, The University of Michigan, 181 EWRE Building, 1351 Beal Avenue, Ann Arbor, Michigan 48109-2125, USA.
Environmental Science & Technology
|September 5, 2003
Summary
Synthetic surfactants enhance polycyclic aromatic hydrocarbon (PAH) solubilization but reduce bioavailability. Microbes preferentially degrade surfactants, destabilizing micelles and releasing PAHs, impacting bioremediation strategies.
Area of Science:
- Environmental Microbiology
- Environmental Chemistry
- Bioremediation
Background:
- Synthetic surfactants, like Tweens, are used to enhance the solubility of hydrophobic contaminants such as polycyclic aromatic hydrocarbons (PAHs).
- The bioavailability of these solubilized contaminants to microorganisms is crucial for effective bioremediation.
- Understanding surfactant-PAH interactions and microbial degradation pathways is key to optimizing bioremediation processes.
Purpose of the Study:
- To investigate the impact of biodegradable nonionic Tween surfactants on phenanthrene bioavailability in micellar solutions.
- To characterize the changes in surfactant properties and micelle structure due to microbial degradation.
- To assess the implications of these findings for surfactant-enhanced bioremediation.
Main Methods:
- Utilized micellar solutions without soil or sediment.
- Employed the PAH-degrading bacterium Sphingomonas paucimobilis EPA 505.
- Measured surface tension, critical micelle concentrations (CMCs), and weight-based PAH solubilization ratios.
- Characterized surfactants using High-Performance Liquid Chromatography (HPLC) and assessed emulsification behavior.
Main Results:
- Surfactants significantly increased phenanthrene solubilization above their CMCs.
- Micellar-solubilized phenanthrene was not readily bioavailable to Sphingomonas paucimobilis EPA 505.
- Microorganisms preferentially utilized hydrophobic fractions of Tween surfactants, destabilizing micelles.
- Released phenanthrene reverted to a crystallized form, requiring re-dissolution for bioavailability.
Conclusions:
- Preferential biodegradation of surfactants by microorganisms destabilizes micelles, releasing PAHs.
- The released PAHs may re-crystallize, limiting immediate bioavailability.
- This study is the first to quantify changes in surfactant micelle properties due to partial biodegradation.
- Findings have significant implications for the application and efficacy of surfactant-enhanced bioremediation of contaminated sites.