As a widely used stabilizer for some chlorinated solvents, 1,4-dioxane (dioxane) has been detected worldwide as a contaminant in surface water and aquifers. Unfortunately, its hydrophilic nature and structural stability preclude effective removal by conventional physical and chemical treatments. Bioremediation, when applicable, is thus the most economical and eco-friendly alternative to mitigate the large and dilute plumes formed by dioxane. A number of bacterial strains have been isolated or identified due to their capability of degrading dioxane via metabolism or cometabolism. A majority of these strains are Gram-positive Actinomycetes belonging to the genera of Rhodococcus, Pseudonocardia, and Mycobacterium. In situ application of these Gram-positive Actinomycetes is limited due to their slow growth and clump forming that hurtles their subsurface distribution in the contaminated aquifers. In this study, we isolate and report the first Gram-negative bacterial strain DD4 that is capable of degrading dioxane with propane as the primary substrate. When fed with propane, DD4 exhibited fast growth and its cell yield was estimated as high as 0.25 mg protein mg propane-1. Dioxane degradation activity of DD4 can be sustained by repeated amendment of propane with little or no clumps formed. Even better, DD4 is able to co-oxidize a variety of toxic volatile organic contaminants that are commonly concurrent with dioxane, such as toluene, 1,1-DCE, cis-1,2-DCE, 1,2-DCA, and VC. Degradation of propane and dioxane were both completely inhibited by the exposure of acetylene, suggesting the involvement of monooxygenase which is under molecular characterization in our lab. Further, microcosm assays with field samples demonstrate DD4 can remove dioxane from 10.4±0.1mg/L to below 0.4 µg/L within 14 days of incubation and overcome the inhibition of the environmental factors (e.g., 1,1-DCE), suggesting the suitability of DD4 as a potent inoculum candidate for in situ bioaugmentation.

Cometabolic degradation of 1,4-dioxane and Co-contaminants by a novel Gram-negative propanotrophic bacterial isolate

256th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.