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Thermally aged PET microplastics disrupt methanogenic syntrophy via toxic leachates: Microbial assembly dynamics unravel biotoxicity in anaerobic digestion
Summary
Researchers found that thermally aged PET microplastics disrupted methane production during anaerobic digestion more severely than pristine microplastics. The aging process increased reactive oxygen species levels and released toxic chemical compounds that interfered with the microbial communities responsible for biogas production, with longer aging periods causing greater inhibition of methane upgrading.
Thermally aging processes for microplastics (MPs) in organic waste commonly occur before anaerobic digestion (AD), potentially influencing microbial community assembly differently compared to primal MPs. In this study, polyethylene terephthalate (PET) MPs were thermally aged under laboratory conditions. Subsequently, morphological analysis, identification of released ingredients, and toxicity assessments for both primal and thermally aged MPs within a biogas upgrading system. The results demonstrated that at a concentration of 60 mg/L, the ultimate CH percentage of upgraded biogas decreased by 2.31 % and 3.43 % after aging durations of 15 and 30 days, respectively, compared to primal PET MPs. Following thermal aging, the reactive oxygen species (ROS) levels in the medium increased, and plasticizer extract of 2,4-Di-tert-butylphenol (DTBP) interacted with the acetyl-CoA decarbonylase/synthase (ACDS), CODH/ACS complex β subunit, which negatively impacted the activity of methanogenic metabolism. Microbial community assembly analysis revealed that the dominant methanogenic syntrophy shifted from acetoclastic to hydrogenotrophic methanogenesis when thermally aged MPs replaced primal MPs. These findings enhance our understanding of how MPs influence microbial metabolism under anaerobic condition, particularly regarding methanogenesis.