Biodegradation of Perfluorooctanoic Acid (Pfoa) by Laccase from Agaricus Bisporus Via Oxidative Decarboxylation

Abstract

Per- and polyfluoroalkyl substances (PFAS) have recently attracted much attention from the public and scientific community due to their undesirable effects to humans and animals and potential for bioaccumulation. Finding possible biological methods for removal and degradation is a critical step to develop environmentally benign approaches to manage their environmental fate, especially in contaminated water bodies. In this study, we demonstrate that perfluorooctanoic acid (PFOA), a model PFAS, can be effectively degraded by enzyme catalyzed oxidative humification reactions (ECOHRs), using 1-hydroxybenzotriazole (HBT) as reaction mediator and laccase from Agaricus bisporus in a continuous reaction at room temperature. Fluoride ions were detected in the reaction samples, indicating the overall defluorination of initial PFOA was up to 95 % in high-concentration enzyme treatment after 55 days. Correspondingly, a significant decrease of the PFOA concentration was observed in respect to the enzyme treatment. Liquid chromatograph-mass spectrometry (LC-MS) analysis also revealed shorter carbon-chain perfluorocarboxylic acids, partially fluorinated shorter-chain alcohols and aldehydes as degradation products. These partially fluorinated compounds resulted from PFOA degradation via a combination of decarboxylation, free radical reactions, reductive defluorination, rearrangement, and coupling processes. These findings prove that PFOA is degraded and transformed during humification, suggesting that the laccase-catalyzed reactions can potentially be used for the bioremediation of PFOA and other PFAS in aqueous environments.

Keywords: Perfluorooctanoic acid, Laccase, Biodegradation, defluorination, mediator