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Fungal Biotransformation of Polyfluoroalkyl Substances: Identification of Growth Substrates for Favorable Biotransformation Pathways

  • Author(s): Merino, Nancy Shiao-lynn
  • Advisor(s): Mahendra, Shaily
  • et al.
Abstract

Polyfluoroalkyl and perfluoroalkyl substances (PFASs) are a group of highly stable organic compounds that provide products with several useful properties, including water, oil, and stain resistance. However, many PFASs are reproductive and developmental toxicants, endocrine disrupters, and potential human carcinogens. They are found globally, such as in contaminated groundwater and surface water and in pristine environments. Since PFAS-containing industrial and consumer products will be disposed into the environment, it is necessary to understand the microbial transformation of these compounds and to develop pollution remediation strategies.

Phanerochaete chrysosporium, a wood-decaying fungus, transformed 6:2 fluorotelomer alcohol (6:2 FTOH), towards less fluorinated polyfluorocarboxylic acids. The most abundant transformation product after 14 days was 5:3 acid (43 mol% of initially applied 6:2 FTOH) when lignocellulosic powder, yeast extract, cellulose, and glucose were added. In addition, four unique 5:3 acid conjugates were identified as products of fungal degradation of 6:2 FTOH. Nutrient supplements, including cellulose, yeast extract, malt extract, glucose, and EDTA, which increase the sulfate and carbon content and trace mineral availability, are necessary for transformation of 6:2 FTOH towards 5:3 acid by P. chrysosporium. These may promote the suite of cytochrome P450 oxygenases and other extracellular enzymes responsible for transforming 6:2 FTOH.

Gloeophyllum trabeum, Trametes versicolor, and several fungal isolates, were also able to transform 6:2 FTOH towards 5:3 acid. While most fungal pure cultures were limited in their ability to transform 6:2 FTOH under the nutrient conditions tested, the resulting metabolites will likely be further transformed in the environment via other biotic or abiotic processes. These studies demonstrate that fungi possess unique biochemical pathways for degrading polyfluoroalkyl substances towards less fluorinated and more biodegradable products. Since manufacturers are increasingly using FTOH-based products, it is necessary to understand the role of various microorganisms on the fate, transport, and transformations of PFASs in the environment.

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