title: Biodegradation Kinetics of 1,4-Dioxane in Chlorinated Solvent Mixtures.
abstract: This study investigated the impacts of individual chlorinated solvents and their mixtures on aerobic 1,4-dioxane biodegradation by Pseudonocardia dioxanivorans CB1190. The established association of these co-occurring compounds suggests important considerations for their respective biodegradation processes. Our kinetics and mechanistic studies demonstrated that individual solvents inhibited biodegradation of 1,4-dioxane in the following order: 1,1-dichloroethene (1,1-DCE) > cis-1,2-diochloroethene (cDCE) > trichloroethene (TCE) > 1,1,1-trichloroethane (TCA). The presence of 5 mg L(-1) 1,1-DCE completely inhibited 1,4-dioxane biodegradation. Subsequently, we determined that 1,1-DCE was the strongest inhibitor of 1,4-dioxane biodegradation by bacterial pure cultures exposed to chlorinated solvent mixtures as well as in environmental samples collected from a site contaminated with chlorinated solvents and 1,4-dioxane. Inhibition of 1,4-dioxane biodegradation rates by chlorinated solvents was attributed to delayed ATP production and down-regulation of both 1,4-dioxane monooxygenase (dxmB) and aldehyde dehydrogenase (aldH) genes. Moreover, increasing concentrations of 1,1-DCE and cis-1,2-DCE to 50 mg L(-1) respectively increased 5.0-fold and 3.5-fold the expression of the uspA gene encoding a universal stress protein. In situ natural attenuation or enhanced biodegradation of 1,4-dioxane is being considered for contaminated groundwater and industrial wastewater, so these results will have implications for selecting 1,4-dioxane bioremediation strategies at sites where chlorinated solvents are present as co-contaminants.
authors.affiliation: Department of Civil and Environmental Engineering, University of California , Los Angeles, California 90095, United States.
authors.forename: Shu
authors.initials: S
authors.lastname: Zhang
authors.affiliation: Department of Civil and Environmental Engineering, University of California , Los Angeles, California 90095, United States.
authors.forename: Phillip B
authors.initials: PB
authors.lastname: Gedalanga
authors.affiliation: Department of Civil and Environmental Engineering, University of California , Los Angeles, California 90095, United States.
authors.forename: Shaily
authors.initials: S
authors.lastname: Mahendra
mesh_terms: D001673:Biodegradation, Environmental; D060587:Groundwater; D007700:Kinetics; D012997:Solvents; D014241:Trichloroethylene; D014874:Water Pollutants, Chemical
chemical_list: D012997:Solvents; D014874:Water Pollutants, Chemical; D014241:Trichloroethylene