Polyolefin colonization and partial degradation by <i>Gordonia</i> sp., and <i>Arthrobacter</i> sp. isolated from wetlands and compost

Abstract Plastics and microplastics constitute an ever-increasing pollutant in the biosphere. There is clear evidence that environmental microbes possess enzyme systems and metabolic apparatus to degrade natural high molecular weight polymers, which substantially overlap with those involved in the biodegradation of plastics. This study investigated the presence and activities of plastic-degrading microbes in environments with a high abundance of plant-derived polymers, including cellulosic, chitinous, or lignin-derived compounds. Microbes were enriched in a minimal medium, with low-density polyethylene (LDPE), polypropylene (PP), poly(ethylene terephthalate) (PET), or polystyrene (PS) as the sole carbon source, resulting in 12 bacterial isolates. Plastic mass loss and cell viability were measured over a 28-day incubation period, in addition to assessment of biofilm formation. Gordonia sp. iso11 displayed mass loss of PP of up to 22.8% and formed a viable dense biofilm (10 9 CFU cm -2 ) on a PP film. A putative alkane-1-monoxygenase (AlkB) was identified from genome sequence analysis, which aligned with a known LDPE-degrading enzyme. Furthermore, reductions in the contact angle of medium supernatant from Gordonia sp. iso11 provided evidence of biosurfactant production which may enhance the bioavailability of the synthetic plastic. To our knowledge, this is the first demonstration of PP degradation by Gordonia .