Plastic Eaters

Plastic Eaters

Researchers discovered and created an improved variant of an enzyme that can break down plastic bottles made of polyethylene terephthalate, or PET. Instead of waiting for over 500 years for plastic to degrade on its own, bacteria only need a couple of days to start eating their way through. The enzyme not only breaks down the produced waste faster, it also brings it back to its original component parts. This allows for much easier recycle and reuse of PET into new and exciting products.

What is bio-based recycling?

Talking about plastic, a lot of people feel overwhelmed and hopeless about the amount of waste we produce. And you can’t blame them. It is estimated that by 2050 there will be more plastics in the high seas than fish. Only 9% of all plastics we use winds up being recycled. And currently, recycling just grinds plastic waste into smaller pieces that are then being reassembled into lower-quality plastic. Plastic litter that ends up offshore or in landfill leaches harmful chemical contaminants into our oceans, soil, food, water and inevitably ourselves.

Entering bio-based recycling. A bacterium, Ideonella sakaiensis 201-F6, was discovered in the soil of a Japanese PET bottle recycling plant. This organism could eat its way through polyethylene terephthalate, or simply PET. While doing so, these plastic-eating organisms squirted out an enzyme, PETase, that stripped the polymer into chemical pieces. This is nothing new though. Biologists have already discovered enzymes spit out by fungi and microbes that can break down PET and nylon. Plastics in Lake Zurich have been identified to carry organisms eating polyurethane. There has been fungus discovered which grind there way through PET. But none of these reactions are fast enough to be used on an industrial scale.

Researchers from the National Renewable Energy Lab, Colorado, and the United Kingdom’s University of Portsmouth, created an improved variant of this enzyme that break down PET bottles much faster. Combining these improved organisms and temperatures of more than 400 degrees could become the recipe for a bio-based PET recycling process. These recycling plants heat up plastic and add some PET hungry PETase or enzyme. This process depolymerises 100% amorphous PET based commercial products into its original monomers, terephthalic acid and mono ethylene glycol. Companies can use these original building blocks to be assembled into something more valuable than the original and catalyse a true circular economy.

How is it eco-friendly?

Being able to bring plastic back to its original building blocks creates real economic incentives to reclaim polymers. Currently, recycling PET generates weaker bonds which can’t be used to manufacture a new bottle or another high value product. Instead, these plastics are worth only 75% of their original value and find their purpose in textiles and carpets. Breaking down plastics using bio-based recycling, allows the original components to be produced into high value materials like Kevlar and sold up to 3 times the value of recycled PET. This gives companies cash incentives to reclaim and repurpose plastics in new products. In turn, it reduces our needs for additional oil drilling and the amount of plastic waste floating in rivers, oceans and piling up on our landfills.

However, as with a lot of processes, during digestion carbon is been spit out. This carbon eventually becomes carbon dioxide, a well-known greenhouse gas contributing to climate change. But the amount of carbon dioxide emitted would be dwarfed by gases from other industries. Even better, as outcome of this process, regenerated original components could be assembled into very valuable products like wind turbines and solar panels. Balancing out the (re)use of plastics and a bio-warmed planet.
This animation shows a 360-degree rotation of the crystal structure of PETase (in green) with a docked PET polymer (in yellow) bound to the active site. The research team used this 3-D information to better understand how PETase works, which led to engineering an enzyme even better at degrading plastic. Animation by Professor John McGeehan / University of Portsmouth