White Rot Fungi Produce Novel Tire Wear Compound Metabolites and Reveal Underappreciated Amino Acid Conjugation Pathways

There is increasing concern about tire wear compounds (TWCs) in surface water and stormwater as evidence grows on their toxicity and widespread detection in the environment. Because TWCs are prevalent in stormwater, there is a need to understand fate and treatment options including biotransformation in green infrastructure (e.g., bioretention). Particularly, fungal biotransformation is not well-studied in a stormwater context despite the known ability of certain fungi to remove recalcitrant contaminants. Here, we report the first study on fungal biotransformation of the TWCs acetanilide and hexamethoxymethylmelamine (HMMM). We found that the model white rot fungus, Trametes versicolar, removed 81.9% and 69.6% of acetanilide and HMMM, respectively, with no significant sorption to biomass. The bicyclic amine 1,3-diphenylguanidine was not removed. Additionally, we identified novel TWC metabolites using semi-untargeted metabolomics via high-resolution mass spectrometry. Key metabolites include multiple isomers of HMMM biotransformation products, melamine as a possible dead-end product of HMMM (verified with an authentic standard), and a glutamine-conjugated product of acetanilide. These metabolites have implications for environmental toxicity and treatment. Our discovery of the first fungal glutamine-conjugated product highlights the need to investigate amino acid conjugation as an important pathway in biotransformation of contaminants, with implications in other fields including natural products discovery.

Automated summary

There is growing concern about tire wear compounds (TWCs) in surface water and stormwater due to their toxicity and presence in the environment. This study focused on fungal biotransformation of TWCs in stormwater, specifically acetanilide and hexamethoxymethylmelamine (HMMM). The white rot fungus, Trametes versicolar, was found to effectively remove acetanilide and HMMM, indicating a potential treatment option. The study also identified novel metabolites of TWCs, which have implications for environmental toxicity and treatment.