Biodegradation of Per- and Polyfluoroalkyl Substances (PFASs) via Superoxide-Hyper-Producing Bacteria

Pedro Alvarez | Rice University



Superoxide has been shown to degrade and defluorinate PFOA, and evidence suggests it may play a critical role in the degradation of other per- and polyfluoroalkyl substances (PFAS). It was also recently discovered that many heterotrophic bacteria produce extracellular superoxide, with production rates spanning several orders of magnitude between different species. Moreover, superoxide production can be enhanced by the presence of cofactors (e.g., up to 100-fold using NADH), and its reactivity can be increased by certain solid matrices (with high surface area), redox mediators, or low polarity solvents. Therefore, we hypothesize that bacteria capable of producing high concentrations of superoxide can be used as a basis for PFAS bioremediation strategies. The objective of this proof-of-concept project is to identify bacterial strains that are capable of producing superoxide at high rates and assess their capacity to degrade model PFAS.

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Technical Approach

PFAS degradation will be assessed under various conditions in a low complexity, controlled system using enzymatically-generated superoxide. Second, heterotrophic bacteria will be screened to identify the highest superoxide-producing strains (hyper-producers), and assess their ability to degrade PFAS (PFOA, PFOS, 8:2 fluorotelomer alcohols [FTOH]) under conditions identified as maximally enhancing superoxide production and reactivity. Finally, PFAS degradation by superoxide hyper-producers will be assessed using PFAS-spiked aquifer material.

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The identification and characterization of superoxide hyper-producing bacteria will facilitate the development of both in situ and ex situ bioremediation strategies and is expected to lead to significantly reduced treatment costs. Project results will also improve the understanding of potential natural attenuation routes (via extracellular reactive species) and how biostimulation might be used to enhance their efficacy and increase biodegradation rates. Moreover, this strategy is likely to prove useful for the remediation of a wide range of recalcitrant contaminants.

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Javed, H. 2020. Mechanistic Insights on the Merits and Limitations of Advanced Treatment Processes for Removal of Contaminants of Emerging Concern. (Ph.D. Dissertation). Rice University, Houston, TX.

Javed, H., C. Lyu, R. Sun, D. Zhang, P. J. J. Alvarez. 2020. Discerning the Inefficacy of Hydroxyl Radicals during Perfluorooctanoic Acid Degradation. Chemosphere, 247:125883.

Javed, H., J. Metz, T. C. Eraslan, J. Mathieu, B. Wang, G. Wu, A. L. Tsai, M. S. Wong, P. J. J. Alvarez. 2020. Discerning the Relevance of Superoxide in PFOA Degradation. Environmental Science & Technology Letters, 7(9):653–658.

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Points of Contact

Principal Investigator

Dr. Pedro Alvarez

Rice University

Phone: 713-348-5903

Program Manager

Environmental Restoration