Biological Plastic Degradation

Plastic pollution has been a major problem in waste management as more than 275 million metric tons have been generated around the world since 2010. Most of it ends up in the ocean due to mismanagement in landfills, and while many resolutions have been implemented, little has been met with long term success.

Polyethylene terephthalate (PET) is a condensation polymer used in plastic that is highly resistant to biodegradation. It is industrially produced by either terephthalic acid or dimethyl terephthalate with ethylene glycol. Common uses for PET plastics include soda bottles, bakery products, water bottles, peanut butter jars, as well as for storage of cosmetic products and household cleaners. It takes at least 450 years to completely degrade even a small plastic water bottle. Thus there has been a major need for an accelerated method of plastic degradation.

In 2016, the Oda group at Kyoto Institute of Technology discovered a microbe that was able to metabolize PET. This microbe, called Ideonella Sakaiensis, produces an enzyme (PETase) that breaks down PET into terephthalic acid and ethylene glycol. The discovery of a microbe that is capable of breaking down PET introduces a non-toxic and sustainable way of degrading PET plastics.   

At an international synthetic biology competition shortly after the PETase enzyme was discovered, a team at Harvard University designed a plastic-sensing system that gives feedback on where PET is located in the ocean. The system is comprised of two components: the microbe which breaks down PET, and a microbial fuel cell which uses the TPA byproduct as a carbon source to generate an electrical signal. A GPS ping can be sent to researchers that PET is present in the devices’ location. This not only breaks down PET, but also sends valuable feedback to researchers about the distribution of plastic waste in the ocean. For instance, is the plastic accumulated on the surface, in the depths, or in sediment?

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