| Abstract | INTRODUCTION: Plastic pollution and energy recovery are often treated as separate challenges. Plastics are highly durable, hydrophobic, and crystalline, making them ideal for disposable products but resistant to natural degradation, allowing waste to persist for decades (Pilapitiya and Ratnayake, 2024). Most single-use plastics fragment into micro- and nanoplastics, posing environmental and health risks, yet they also represent a low-cost carbon resource. Biological systems offer a promising solution, as microbes can metabolically degrade plastics into simpler compounds. While aerobic PET degradation is slow due to high crystallinity and low enzymatic activity, anaerobic conditions may induce alternative degradation pathways (Kalathil et al., 2022). This study investigates whether a coculture of Ideonella sakaiensis and Shewanella oneidensis can degrade PET microplastics in a microbial fuel cell, converting them into metabolites and electricity. MATERIALS & METHODS: The anaerobic fermentation of PET in a microbial fuel cell was evaluated using FTIR, weight-loss measurements, and scanning electron microscopy. Electrochemical performance and soluble COD were monitored to assess microbial activity, while degradation products were identified and quantified using HPLC and GC–MS to elucidate PET degradation pathways. RESULTS: Over a 40-day period, three microbial fuel cell systems were evaluated: Shewanella oneidensis monoculture, Ideonella sakaiensis monoculture, and their coculture. The S. oneidensis monoculture achieved 9.2% PET biodegradation, producing acetic acid and generating a power density of 1.01 mW/m². In contrast, I. sakaiensis degraded 35.2% of PET, producing acetic acid and ethanol with a power density of 1.17 mW/m². The coculture showed moderate PET degradation (16.4%) and yielded a power density of 0.202 mW/m². SEM analysis revealed that control PET exhibited minimal surface changes, whereas PET exposed to microbial treatments developed pronounced pits, cracks, and fissures, along with extensive biofilm formation, confirming active depolymerisation and microbial attachment. S. oneidensis surfaces displayed microbial colonies and debris, whereas I. sakaiensis surfaces were highly porous and brittle. Soluble COD measurements supported these trends, with the highest values in I. sakaiensis monoculture (433.36 mg/L), followed by S. oneidensis (328.8 mg/L) and coculture (303.15 mg/L), compared to the control (44.85 mg/L). FTIR analysis indicated carbonyl oxidation, ester bond hydrolysis, and cleavage of aromatic linkages, with hydroxyl and amine exposure confirming microbial contribution. Overall, I. sakaiensis anaerobically ferments PET into metabolites while generating electricity, and S. oneidensis oxidises acetate to current. Coculture performance was lower, highlighting interspecies interactions that can limit the efficiency of MFC-based PET bioremediation and energy recovery. CONCLUSION: This study demonstrates that Ideonella sakaiensis can anaerobically degrade PET microplastics into ethanol and acetate while generating electricity, a previously unreported electrochemical activity. Shewanella oneidensis also contributed to PET degradation. Coculture revealed antagonistic interactions, highlighting that microbial dynamics can limit efficiency, yet microbial fuel cells remain promising for PET remediation and energy recovery. REFERENCES: Pilapitiya, P.G.C.N.T. and Ratnayake, A.S. (2024). The World of Plastic waste: a Review. Cleaner Materials, [online] 11(2772-3976), p.100220. doi:https://doi.org/10.1016/j.clema.2024.100220. Kalathil, S., Miller, M. and Reisner, E. (2022). Microbial Fermentation of Polyethylene Terephthalate (PET) Plastic Waste for the Production of Chemicals or Electricity. Angewandte Chemie (International Ed. in English), [online] 61(45), p.e202211057. doi:https://doi.org/10.1002/anie.202211057. |
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