A combined thermodesorption and pyrolysis GC–MS approach reveals fragmentation and depolymerization products during plastic biodegradation

While the degradation of plastics into molecules and micro- and nanoplastics (MNPs) through abiotic processes is increasingly well documented, bacterial-driven biodegradation remains poorly understood. Yet, as microbial strategies to mitigate plastic pollution gain traction, identifying the full spectrum of degradation products, from soluble molecules to microplastics and nanoplastics, is essential for elucidating both toxicological impacts and fundamental degradation mechanisms. In this study, we developed an integrated analytical method combining thermodesorption and pyrolysis gas chromatography–mass spectrometry (TDS/Py-GC-MS). A tailored liquid–liquid extraction protocol was optimized for both polymers and applied to culture media containing microbial communities in contact with solid plastic samples. This approach enabled the identification of specific depolymerization products from polystyrene (PS) and polyvinyl chloride (PVC), including known markers (e.g., phthalic anhydride, 2-ethylhexan-1-ol, acenaphthene) and novel aromatic compounds likely associated with microbial activity, such as (1E)-1-benzylideneindene, 2-ethylcyclopentan-1-one, and benzene in samples from superworms intestinal microbiota cultivated with PS or PVC film at different temperature (n = 1). In terms of fragmentation, PS particles were recovered in varying quantities, while no PVC fragments were detected. This study provides a robust analytical framework to characterize plastic degradation and identify molecular markers of degradation.