Hunting for thermophilic plastic-active enzymes in a local wastewater treatment plant

Plastic demand has drastically increased in the last decades, but little has been done to reduce its environmental impact. Most plastic waste is disposed of in landfi lls or dispersed, thus polluting terrestrial and marine environments[1]. Microbes thriving in these ecosystems may represent a reservoir of plastic-degrading enzymes. Therefore, we investigated the plastic-degradation potential of microbes isolated from a microplastic-abundant environment, i.e., a local municipal wastewater treatment plant. Cultivation media, containing post-consumer polyethylene terephthalate (PET) or polylactic acid (PLA), were used to favor the growth of mesophilic and thermophilic plastic-degrading microbes. In parallel, biofi lm-forming and planktonic cells were sub-enriched on PET or PLAemulsifi ed agar plates[2]. Enriched consortia were screened on plates containing either short-chain (esterase-like enzyme activity) or middle-chain length triglycerides (lipase-like enzyme activity) to isolate producers of soluble plastic-degrading enzymes[3]. As a result, we have isolated several strains secreting esterase- and lipase-like enzymes, which are currently under investigation to assess their PET- and/or PLA-degradation activity via enzymatic assays[4], using plastics emulsions as substrates. Moreover, zymography, 3D fl uorescence, and degradation assays will be performed to identify and characterize potential enzymes active on post-consumer plastic waste residues.