Biodegradation of micro-polyethylene particles by bacterial colonization of a mixed microbial consortium isolated from a landfill site

In this study, we investigated the decomposition of micro-sized polyethylene (PE) by mesophilic mixed bacterial culture isolates obtained from a municipal landfill sediment. Among these, Bacillus sp. and Paenibacillus sp. were more specifically enriched in the non-carbonaceous nutrient medium (i.e., Basal medium) as they were the most dominant species when they were exposed to PE microplastics. They reduced the dry weight of particles (14.7% after 60 d) and the mean particle diameter (22.8% after 60 d; obtained by field-emission scanning electron microscopy analysis). In the gas chromatography-mass spectrometer analysis of biologically aged particles, the amount and types of organic contents eluted from the PE microplastics were far lower in the early decomposition phase; however, they increased in the later phase. Thermal gravimetric analysis showed that the aged particles had higher thermal stability at temperatures greater than 570 °C compared to the control, thereby suggesting that microplastics were degraded by enzymatic chain scission, which could in turn be ascribed to the greater refractory fractions of aged particles remaining at a high combustion temperature. It was further verified that PE particles could be biologically utilized as a sole carbon source and broken down during the test period.