In an article published on March 11, 2016 in the peer-reviewed journal Science, Shosuke Yoshida and colleagues from the Department of Polymer Chemistry, Graduate School of Engineering of Kyoto University, Japan, report on the isolation of a bacterium that can degrade and assimilate polyethylene terephthalate (PET).
From soil samples collected around a PET recycling factory, the researchers isolated a new species they named Ideonella sakaiensis. This bacterium is capable of “almost completely” degrading thin PET film after 6 weeks. According to the commentary by Uwe Bornscheuer (in Science), supported by Matthew Gunther (in Chemistry World), this microorganism “may be advantageous for removing [PET] material from the environment.” It is noteworthy, however, that the reported process is aerobic and occurs at 30°C. Hence, it remains to be investigated still whether PET degradation of the same efficiency would occur in aquatic environments, where PET plastic commonly accumulates. Due to its specific density, PET would sink to the ground, facing conditions with much lower temperature and oxygen content.
The two enzymes, “PETase” and “MHETase”, catalyzing the pathway that breaks the polymer chain into its monomers (ethylene glycol and terephthalic acid), could also be isolated and characterized. These enzymes could be advantageous to recycling, as their high specificity could allow extracting PET monomers even from “mixed plastics waste or from composite materials”, according to Georg Guebitz, head of the Institute of Environmental Biotechnology at the University of Natural Resources and Life Sciences, Austria. To enable such application, the production of necessary amounts of active PETase/MHETase enzymes would need to be ensured, likely by genetic engineering methods.
PET plastics, mostly produced from crude oil, are used in a variety of materials, including PET beverage bottles. Recycling of PET is common and generally achieved through mechanical or chemical processes (see FPF dossier on plastics recycling). If ending up in the environment, PET plastics degrade very slowly and commonly do not undergo a complete mineralization (i.e. degradation into CO2).
Bornscheuer, U. (2016). “Feedig on plastic.” Science 351:1154-1155.
Matthew Gunther (March 11, 2016). “Plastic-eating bacteria show way to recycle plastic bottles sustainably.” Chemistry World
Yoshida, S. et al. (2016). “A bacterium that degrades and assimilates poly(ethylene terephthalate).” Science 351:1196-1199.