Postdoctoral fellow Courtney Toth and team have developed unique anaerobic cultures that degrade a toxic set of petroleum hydrocarbons known as BTEX – Benzene, Toluene, Ethylbenzene, and Xylene.
It’s no secret we are amid a growing pollution crisis. Anywhere that we produce, use, or store hazardous chemicals is at risk of contamination. Fortunately, nature has developed a powerful solution – microorganisms uniquely adapted to “eat away” at pollution. These microbes, which consist primarily of bacteria, are widespread in nature and are capable of degrading many classes of organic pollutants.
Under the supervision of Professor Elizabeth Edwards, the team – consisting of Courtney and over 25 talented students, technicians, postdocs, principal investigators, and industry scientists from across Canada – are focused on BTEX-eating microbes, as thousands of sites in Canada are contaminated with BTEX including old gas stations and orphaned oil wells.
“Like humans, many species of BTEX-degrading bacteria need oxygen to breathe. The challenge is that most BTEX contamination exists in the subsurface, where oxygen is limited. To clean these sites, aeration methods are often too labour-intensive and costly to implement, limiting the number of sites that ultimately get cleaned up,” explains Courtney.
Her team’s approach takes advantage of a subset of bacteria that can break down BTEX without access to oxygen, in a process known as anaerobic degradation. Anaerobic BTEX degraders are commonly found in contaminated subsurface environments but for unknown reasons their numbers are often too few to drive substantial BTEX degradation. Using specialized drilling equipment to inject the cultures deep underground into plumes of hydrocarbon contamination, the group has been able to increase the numbers to a sufficient level for the microbes to do the rest.
This project is the culmination of over 30 years of research in anaerobic hydrocarbon degradation, and a 20-year partnership between Professor Edwards and SiREM, an environmental remediation laboratory in Guelph, Ontario.
Each culture, which started out as a small bottle of contaminated soil and groundwater, has been maintained for decades on a strict diet consisting only of BTEX. Dozens of lab experiments conducted by generations of students and scientists, proved that the cultures degrade BTEX. In 2016, the cultures were brought to SiREM for large volume scale-up suitable for field deployment. Genome-based monitoring tools were developed to accurately track the role and fate of each microorganism in each culture. Before any field trial, massive documents (>300 pages each) had to be drafted to obtain federal approval to manufacture and sell the BTEX-degrading cultures in Canada.
Currently, six field pilots are underway across North America, including three in Canada. Three of these sites have begun to show promising evidence of enhanced anaerobic BTEX degradation after only one-three years since the culture addition. These sites will continue to be monitored for as long as possible to validate current trends.
Due to rapid interest in the approach, the BTEX-degrading cultures have been commercialized by SiREM under the brand name DGG™ Plus, in homage to microbiologist Dunja Grbić-Galić who helped pioneer the field of anaerobic hydrocarbon degradation. Additionally, Courtney received the 2022 Mitacs Award for Commercialization for her role in helping to bring this research to market.
By speeding up natural degradation processes, this new technology could feasibly shave years off remediation timelines and save millions of dollars in site management costs. It’s a win-win for industry and environmental health.