title: Biodegradation of 1,4-dioxane: effects of enzyme inducers and trichloroethylene.
abstract: 1,4-Dioxane is a groundwater contaminant and probable human carcinogen. In this study, two well-studied degradative bacteria Mycobacterium vaccae JOB5 and Rhodococcus jostii RHA1 were examined for their 1,4-dioxane degradation ability in the presence and absence of its co-contaminant, trichloroethylene (TCE), under different oxygenase-expression conditions. These two strains were precultured with R2A broth (complex nutrient medium) before supplementation with propane or 1-butanol to induce the expression of different oxygenases. Both propane- and 1-butanol-induced JOB5 and RHA1 were able to degrade 1,4-dioxane, TCE, and mixtures of 1,4-dioxane/TCE. Complete degradation of 1,4-dioxane/TCE mixture was observed only in propane-induced strain JOB5. Inhibition was observed between 1,4-dioxane and TCE for all cells. Furthermore, product toxicity caused incomplete degradation of 1,4-dioxane by 1-butanol-induced JOB5. In general, the more TCE degraded, the greater extent of product toxicity cells experienced; however, susceptibility to product toxicity was found to be both strain- and inducer-dependent. The findings of this study provide fundamental basis for developing an effective in-situ remediation method for 1,4-dioxane-contaminated ground water and the first known study of 1,4-dioxane degradation by wild-type strain RHA1.
authors: Zachry Department of Civil Engineering, Texas A&M University, College Station, TX 77843-3136, USA.
authors: Steven
authors: S
authors: Hand
authors: Zachry Department of Civil Engineering, Texas A&M University, College Station, TX 77843-3136, USA.
authors: Baixin
authors: B
authors: Wang
authors: Zachry Department of Civil Engineering, Texas A&M University, College Station, TX 77843-3136, USA. Electronic address: kchu@civil.tamu.edu.
authors: Kung-Hui
authors: KH
authors: Chu
mesh_terms: D001419:Bacteria / Q000378:metabolism*; D001673:Biodegradation, Environmental; D004146:Dioxanes / Q000032:analysis / Q000378:metabolism*; D004790:Enzyme Induction; D060587:Groundwater / Q000737:chemistry* / Q000382:microbiology; D010105:Oxygenases / Q000378:metabolism*; D014241:Trichloroethylene / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000378:metabolism*
chemical_list: D004146:Dioxanes; D014874:Water Pollutants, Chemical; D014241:Trichloroethylene; D010105:Oxygenases; C025223:1,4-dioxane
keywords: 1,4-Dioxane; Bioremediation; Cometabolic degradation; Oxygenases; Product toxicity; TCE