Tue Kjærgaard Nielsen

Project title

Solving Microbial Degradation of PFAS

What is your project about?

PFAS – also known as "forever chemicals" – are among the most persistent and problematic environmental pollutants in the world. They are found in everything from drinking water and soil to the human body, and their chemical stability makes them extremely difficult to break down. This project challenges the very idea that PFAS are indestructible by discovering new bacteria and enzymes that can degrade them. To this end, I will use, among other things, machine learning and characterization of microbial communities in PFAS-contaminated soils in Denmark. The next obstacle to effective degradation is that fluoride is released when the characteristic carbon-fluorine bonds in PFAS are broken. Fluoride is toxic to bacteria, so PFAS degraders end up poisoning themselves. Therefore, I will investigate whether bacteria can be transformed into PFAS degraders if given the right tools, including increased tolerance to fluoride.

How did you become interested in your particular field of research?

Ever since my MSc thesis project, I have been working with bacteria and how they can develop the ability to break down man-made pollution. I have been especially fascinated by how their genetics can adapt incredibly quickly, allowing new traits to emerge. My previous research has focused on pesticide degradation and related topics, but PFAS is a much bigger problem because it is far more difficult to break down. When PFAS started receiving more general attention and were labeled as “forever chemicals,” I felt challenged to do something about it. It is certainly a big undertaking, but the field is so unexplored that new and exciting theories and results are constantly emerging. I am generally strongly motivated by the desire to develop sustainable biosolutions for the future.

What are the scientific challenges and perspectives in your project?

There are several challenges associated with PFAS-degrading bacteria, which stem from how difficult these substances are to break down. Compared to many other fields within microbiology, there is therefore a goldmine of unanswered questions waiting to be explored. We still know very little about which bacteria and enzymes can degrade PFAS, as well as what other challenges prevent natural degradation. In addition, there are thousands of different types of PFAS, and there are likely specific challenges associated with each of them. My project focuses on some of the most widespread PFAS compounds and aims to answer fundamental questions that may eventually lead to the sustainable removal of PFAS from the environment.

What is your estimate of the impact, which your project may have to society in the long term?

There is an urgent lack of sustainable ways to remove PFAS from the environment. Most types of PFAS can be removed from drinking water using (advanced) filtration, but for contaminated soil or sludge, it is more complicated. For example, PFAS-contaminated soil can be heated over a long period or incinerated in specialized facilities to remove PFAS, but this is not sustainable. If microbial degradation can be stimulated or degraders can be added to contaminated soil or sludge, we can achieve sustainable PFAS removal and prevent it from entering the groundwater. Although filtration is effective for most types of PFAS, there is now particular attention on the compound TFA, which is difficult to remove from water and is found in our drinking water. Results from this project could also contribute to future solutions for the problematic TFA.

Which impact do you expect the Sapere Aude programme will have on your career as a researcher?

Receiving a Sapere Aude grant is of critical importance to my career, as I am currently in the middle of my tenure track at the University of Copenhagen and preparing to establish my own research group. In many ways, this project represents the culmination of my research to date, where I will combine my expertise in microbial degradation of pollution, bioinformatics, and DNA sequencing to move closer to sustainable PFAS removal. The grant will enable me to establish myself as a leading researcher in microbial environmental biotechnology. At the same time, the project will strengthen Danish research in biosolutions on an international scale. Denmark is already a frontrunner in many aspects related to PFAS, and this project will only reinforce our position.

Background and personal life

I live in Farum with my wife and two children. It is important for me to maintain a clear boundary between work and family life, although it can sometimes be difficult to set aside thoughts about exciting new results or ideas. Both my wife and I are biologists by education, and we love taking the children out into nature to show them how fascinating it can be. In addition to my family, I have a large group of close friends whom I really enjoy spending time with. Besides research, I also love teaching and communicating science to the broader public.