Collaborative Research: Discovering enzymatic pathways to break carbon fluorine bonds in perfluorinated carboxylic acids

About This Grant

PFAS is a group of chemicals that are costly to remove from the environment. They do not break down naturally in soil and water because of the strong carbon-fluorine bonds. This project will take a new approach toward remediating PFAS by engineering special enzymes that can degrade these stable chemical bonds. If successful, the outcomes of the project could unlock exciting technologies for carbon-fluorine bond destruction, saving money and protecting human health and the environment. Long-term application of the enzymes could break down fluorinated chemicals in soil, drinking water, groundwater, biosolids produced from wastewater sludge, and industrial waste streams. Undergraduates will gain experience as part of the research team. Fluorinated organics, like perfluoroalkyl carboxylic acids (PFCAs), are common industrial additives which persist in the environment and have limited, expensive, and energy-intensive destruction technologies. So far, efforts to degrade PFCAs enzymatically have stalled, due to strong C-F bonds and a lack of evolutionary pressure to reward their destruction. As a result, PFCAs and other per- and polyfluoroalkyl substances (PFAS) are increasingly contaminating environmental media and require removal. Therefore, there is a critical need for new techniques to identify and enhance enzymatic defluorination mechanisms. This project adopts a new approach to discover and improve enzymatic defluorination, positing that proper evolutionary incentive and high-throughput screening techniques can create and discover biocatalysts that degrade perfluorinated carbon chains. The new approach uses a genetic circuit that links survival with defluorination to engineer defluorinases to degrade new substrates. Di- and tri-fluoroacetate will be targeted initially and later the substrate scope will be expanded to include PFCAs. The research will advance fundamental knowledge about enzymatic defluorination by uncovering beneficial mutations in catalytic proteins at the amino acid level, and, thereby, tunable mechanisms to enhance the desired reactions. If successful, the project will enable enzymatic defluorination of a perfluorinated carbon with mechanistic resolution for the first time. Putative defluorinating enzymes, identified in bulk defluorinating biological systems, will be expressed and characterized for activity towards multiple substrates. The successful completion of this project would establish new pathways for defluorination of perfluorinated carbon chains, opening the door for further enzymatic defluorination research and sustainable water treatment options. Finally, through a dedicated laboratory exchange, undergraduates from a primarily undergraduate institution (PUI) will engage in research training and mentoring to gain experience at a university with very high research activity (R1), and a graduate student will oversee student researchers at the PUI, gaining experience in undergraduate education and mentoring. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.