Plastic additives enrich diverse bacterial communities which show the hallmarks of plastic degradation

Plastics contain a variety of chemical additives that enhance their performance but often pose environmental risks due to their persistence and leaching. Microbial degradation offers a promising strategy to mitigate these pollutants, yet efficient methods to identify active degraders remain limited. This project aims to combine biochemical assays with 16S rRNA amplicon sequencing to screen microbial communities for plastic additive biodegradation. Inocula from natural (Chessel Bay, Swansea Bay) and anthropogenic (Wastewater Plant, Recycling Plant) environments were enriched for 22 days, using di(2-ethylhexyl) terephthalate (DEHT) and tetradecane and compared to negative controls. We adapted high-throughput assays to measure community-level growth, death, redox, and esterase activity. DEHT yielded the highest growth, while tetradecane enhanced redox activity. 16S rRNA amplicon sequence analysis identified 957 amplicon sequence variants across 36 cultures. PERMANOVA showed that the substrate explained 39%-63% of the variance in community structure. Both additives enriched bacterial families known to degrade plastics (e.g. Nocardiaceae, which correlated with esterase activity). Other bacterial families not previously associated with plastic degradation (e.g. Vermiphiliaceae) highlight potential for plastic and additive biodegradation. These results demonstrate that diverse environmental microbiomes can metabolize ester- and alkane-based plastic additives. Our methods enable scalable screening of biodegradative communities for bioremediation applications.