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Microbes make a meal of PET

| By Tetsuo Satoh

Research groups at Keio University (Hiyoshi; and Kyoto Institute of Technology, in collaboration with Teijin Ltd. and Adeka Corp., have discovered a bacterium that can degrade and assimilate poly(ethylene terephthalate) (PET), and have clarified the decomposition mechanism. This is said to be the first observation of the biodegradation of PET, which had been deemed to be highly stable and resistant to microbial degradation.

PET is used extensively in plastic products around the world, and its accumulation in the environment has become a global concern. Because the ability to enzymatically degrade PET has been thought to be limited to a few fungal species, biodegradation is not yet a viable remediation or recycling strategy.

By screening natural microbial communities exposed to PET in the environment, the researchers isolated a novel bacterium, Ideonella sakaiensis 201-F6 (found near Sakai, Osaka), which can metabolize PET as its major energy and carbon source. When grown on PET, this strain produces two enzymes, PETase and MHETase, capable of hydrolyzing PET and the reaction intermediate, mono(2-hydroxyethyl) terephthalic acid (MHET). Both enzymes are required to enzymatically convert PET efficiently into its two environmentally benign monomers, terephthalic acid and ethylene glycol.

The researchers believe the biological route offers a viable PET-recycling alternative to existing thermal-degradation methods, which need more energy.