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Credit: Ashanti Alvarez
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Max Häggblom’s laboratory has taken an important step on the path to using microbes to rid the environment of methyl tertiary-butyl ether (MTBE), a toxic gasoline additive now classified as a potential human carcinogen.
In a February 2006 paper in Applied and Environmental Microbiology, the researchers bring to light a tool that could help them find the key bacteria capable of breaking down MTBE. The additive has contaminated virtually all groundwater in the United States through fuel spills and leaking underground gasoline storage tanks.
“While gasoline hydrocarbons are much more toxic than MTBE, they are just candy to microbes and don’t become as persistent a problem,” said Häggblom, a professor in the department of biochemistry and microbiology and the Biotechnology Center for Agriculture and the Environment on the Cook campus.
Since MTBE contamination is underground, anaerobic bacteria – those that operate in the absence of oxygen – are the most likely candidates for the cleanup job. The paper establishes a way to facilitate their use by employing carbon isotope fractionation: the changes in the isotopic ratios of carbon (its different molecular versions, carbon-12 and carbon-13) brought about by the selective degradation of the carbon-12 form in the case of MTBE.
When the ratio of carbon-12 to carbon-13 decreases, it indicates the presence of the kind of bacteria the researchers are looking for. “This approach also will help us eventually home in on precisely which bacterium is doing the eating – possibly the best choice for large-scale underground applications," Häggblom says.
Häggblom and his coworkers are characterizing the community of bacteria feeding on MTBE in their cultures, and, based on initial analyses, there appear to be a dozen or so players. It remains unclear if just one bacterium or several are doing the job; perhaps one or more of them may just be feeding on the waste products of the main degrader or degraders. But Rutgers researchers are getting closer to answering these questions, and thereby making the anaerobes a practical solution to remediation of MTBE-contaminated groundwater.
Producers have been adding MTBE to gasoline since 1979 as an octane-boosting replacement for tetraethyl lead, a major contributor to toxic levels of lead in the environment. MTBE is also blended into winter fuel formulations for colder regions to make the fuel burn more cleanly. Twenty-five states have passed legislation to ban the use of MTBE, with seven more considering its prohibition.
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