AsianScientist (Mar. 28, 2016) – Life in plastic may not be fantastic if it means polluting the planet. Researchers in Japan have discovered a bacterium, Ideonella sakaiensis 201-F6, which uses a common type of plastic polymer as its primary source of carbon for growth. This development offers a whole new way to recycle plastics by breaking them down into their ‘building block’ chemicals. Details of their discovery were published in Science.
Cheap, durable and versatile, polyethylene terephthalate (PET) is used extensively in daily life in a wide range of plastic products. However, as it is non-biodegradable, its accumulation in the environment is fast becoming a global threat. It is harmful to the body too; studies show that endocrine-disrupting chemicals such as antimony can leach into drinking water in PET bottles—although at low, generally-safe levels.
Previously, only a few fungal species have been found to be able to enzymatically degrade PET. Seeking to remedy this, the researchers, led by Dr. Kohei Oda from the Kyoto Institute of Technology and Dr. Kenji Miyamoto from Keio University, collected 250 environmental samples from a PET bottle recycling site, including sediment, soil, waste water and activated sludge to screen for plastic-eating microorganisms.
They found and isolated I. sakaiensis from one of the sediment samples, and discovered the mechanisms with which this strain of bacteria breaks down plastic. When grown on PET film, I. sakaiensis produces two enzymes that convert PET efficiently into its two monomers, terephthalic acid and ethylene glycol, which are both environmentally benign. Remarkably, with the addition of nutrients every two weeks, the PET film was almost completely degraded after six weeks at 30°C.
Furthermore, by identifying the gene responsible for these PET-digesting enzymes, the researchers were then able to produce more of them for further testing.
Currently, post-consumer plastic waste is recycled by being melted down into pellets and reformed. This discovery, if scaled up and developed further, could lead to true recycling systems where plastics are broken down into their chemical components, that can then be used to create new plastic products.
The article can be found at: Yoshida et al. (2016) A Bacterium that Degrades and Assimilates Poly(ethylene Terephthalate).
Copyright: Asian Scientist Magazine; Photo: Rob Sinclair/Flickr/CC.
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