Plastic mineralization by the sooty-mold fungus Capnodium coffeae demonstrated by isotope-tracing and -probing approaches

Plastic pollution represents an increasing environmental burden. Modification of plastic surfaces and degradation by microbes contributes to the removal of plastic from the environment. However, plastic mineralizing organisms are rare, and often mis-classified as such, probably due to the lack of standards. We hypothesize that hydrophobic, waxy surfaces found on tropic leaves that mimic plastic surfaces in terms of hydrophobicity are reservoirs of plastic degrading microbes and developed a standard procedure to unambiguously demonstrate plastic mineralization ¹. A strain of the sooty-mold fungus Capnodium coffeae was isolated and tested on media amended with different plastics resulting in enhanced growth with polystyrene and other common plastics. Capnodium coffeae was incubated together with ¹³C-labelled polystyrene and ¹³CO₂ emissions were followed via cavity ring-down spectroscopy. A continuous increase of polystyrene derived ¹³CO₂ was observed in the headspace indicating polystyrene mineralization. Phospholipid fatty acids stable isotope probing indicated incorporation of polystyrene ¹³C into the fungal biomass and substantiated the polystyrene mineralizing capabilities of C. coffeae. Thus, we successfully isolated a polystyrene mineralizing fungus, and provide a strategy for the assessment of various microbial plastic metabolizers.

¹ Rohrbach, S., Gkoutselis, G., Mauel, A., Telli, N., Senker, J., Ho, A., G. Rambold and M.A. Horn. 2024. Setting new standards: Multiphasic analysis of microplastic mineralization by fungi. Chemosphere 349: 141025. DOI: 10.1016/j.chemosphere.2023.141025