摘要Background Coumarins are toxic phytochemicals found in a variety of plants and are known to limit microbial deg-radation and interfere with nutrient cycling.While the degradation of coumarins by fungi has been studied in an envi-ronmental context,little is known about their degradation in the gastrointestinal system of herbivores after ingestion.Results In this study,we investigated in vitro fermentation by microbial enrichment,transcriptome sequencing,and high-resolution mass spectrometry to evaluate the ability of rumen anaerobic fungi to degrade coumarins.The results showed that despite the low abundance of anaerobic fungi in the rumen microbiota,they were able to effec-tively degrade coumarins.Specifically,Pecoramyces ruminantium F1 could tolerate coumarin concentrations up to 3 mmol/Land degrade it efficiently via metabolic pathways involving alpha/beta hydrolases and NAD(P)H oxidore-ductases within the late growth phase.The fungus metabolized coumarin to less toxic compounds,including o-cou-maric acid and melilotic acid,highlighting the detoxification potential of anaerobic fungi.Conclusions This study is the first to demonstrate the ability of rumen anaerobic fungi to degrade coumarin,provid-ing new insights into the use of anaerobic fungi in sustainable agricultural practices and environmental detoxification strategies.