Utilizing the Plant Microbiome and Bioaugmentation to Degrade 1,4-Dioxane and Co-Contaminants

Dr. Jerald Schnoor | University of Iowa



A persistent and common problem at military bases and some industrial sites is the contamination of groundwater with 1,4-dioxane and co-occurring chlorinated solvents such as trichloroethene (TCE), dichloroethene (DCE), and trichloroethene (TCA). These chemicals are toxic, long-lived, and difficult to biodegrade or treat. They are frequently found at relatively high concentrations in groundwater (mg/L), yet the Environmental Protection Agency has set very stringent clean-up goals (a few μg/L) based on their toxicity and the risk to drinking water supplies. The objective of this project is to discover novel strains of microorganisms to rapidly degrade 1,4-dioxane and co-contaminants to innocuous end-products. We will accomplish this by accessing the microbiome of plants, where we have reason to believe that microorganisms can be found that will biodegrade 1,4-dioxane and co-contaminants better than those reported in the past. With successful isolation, culturing, testing, optimization and scale-up, we will produce and stabilize kg-quantities of the best microbe for bioaugmentation at a contaminated military site.

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Technical Approach

The microbiome (rhizobiome) of plants is an excellent place from which to isolate microorganisms capable of rapidly degrading 1,4-dioxane under site conditions due to the abundance of cytochrome P450 monoxygenase enzymes, encoded by microbial genes in association with model plants likeArabadopsisandPopulusspp. A wealth of monooxygenase enzymes is present in the rhizosphere to ward-off plant predators and to provide oxidative power for intermediate metabolism of carbon compounds provided by photosynthetic plants. At least three strains of bacteria (using diffusion-chamber technology) will be isolated and cultured that will be capable of degrading 1,4-dioxane rapidly as a sole carbon and energy source and/or via co-metabolism in the presence of another substrate like methane, propane, tetrahydrofuran, isobutane, or plant exudates.

ER-2719 graphic

The strains will be used to aerobically degrade 1,4-dioxane and frequently occurring co-contaminants TCE,cis-DCE, 1,1,1-TCA and 1,1-dichloroethane. It is fortuitous that 1,4-dioxane and these co-contaminants are all susceptible to biodegradation by cytochrome P450 monoxygenases and several other oxygensases, although a consortium of microbes and cometabolism with added substrates may be necessary. Following confirmation testing in the laboratory, the production of the best three strains will be scaled up and the best one for bioaugmentation at a military site will be stabilized (lyophilized).

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Using bioaugmentation directly for deep plumes or in-tandem with phytoremediation for shallow plumes offers the optimal prospect for biodegrading recalcitrant contaminated groundwater sites. It is not likely that monitored natural attenuation (MNA) will work because of a scarcity of electron donors for indigenous microorganisms to reach stringent clean-up concentrations. This research takes advantages of synergies by using stabilized, acclimated, and concentrated microorganisms (bioaugmentation) in tandem with phytoremediation as an improved and sustainable remediation strategy. It offers a strategy for difficult groundwater problems, such as dilute large-scale plumes, where it is not practical to perform long-term pump and treat due to the cost and “rebound” from remnant globules of DNAPL. benefits to DoD include improved remediation, cost savings, and the potentially patentable development of a sustainable, green, effective technology. (Anticipated Project Completion - 2020)

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Points of Contact

Principal Investigator

Dr. Jerald Schnoor

The University of Iowa

Phone: 319-335-5649

Fax: 319-335-5660

Program Manager

Environmental Restoration