Biodegradation of Polyethylene Terephthalate (PET) microplastics in a Microbial Fuel Cell

Plastics persist in the environment for centuries, releasing harmful micro- and nanoplastics (MNPs) that threaten ecosystems and may be detrimental to human health. This study investigated the feasibility of a bioelectrochemical approach for the biodegradation and upcycling of polyethylene terephthalate (PET) microplastics. Over 40 days, three microbial fuel cell (MFC) systems were evaluated: (i) Shewanella oneidensis monoculture, (ii) Ideonella sakaiensis monoculture and (iii) their coculture. The S. oneidensis monoculture achieved 9.2% (w/w) PET biodegradation with acetic acid as a metabolite and a power density of 1.01 mW m⁻². The I. sakaiensis monoculture achieved 35.2% (w/w) PET biodegradation with acetic acid and ethanol as metabolites with a power density of 1.17 mW m⁻². The coculture exhibited moderate PET biodegradation (16.4% w/w) and produced acetic acid and ethanol, and a lower power density of 0.202 mW m⁻². These findings demonstrate that Ideonella sakaiensis can anaerobically ferment PET microplastics as the sole carbon source into metabolites including acetic acid and ethanol, while concurrently exhibiting bioelectrochemical activity. Notably, the electroactive bacterium S. oneidensis also exhibited PET-associated biodegradation, supported by PET mass loss and surface deterioration, alongside acetic acid formation and bioelectricity generation, highlighting its potential for the simultaneous biodegradation and bioelectrochemical upcycling of PET microplastics. However, cocultivation of I. sakaiensis and S. oneidensis reduced both PET biodegradation and power generation relative to the best-performing monoculture, suggesting that interspecies competition, antagonistic interactions or metabolic imbalance may limit synergistic activity. Overall, this study demonstrates the potential of MFCs for the simultaneous biodegradation and bioelectrochemical upcycling of PET microplastics, while highlighting the importance of microbial interactions in determining process efficiency.