Scientists create mutant enzyme that recycles plastic bottles in hours

Apr 22, 2020

A mutant bacterial enzyme that breaks down plastic bottles for recycling in hours has been created by scientists.

The enzyme, originally discovered in a compost heap of leaves, reduced the bottles to chemical building blocks that were then used to make high-quality new bottles. Existing recycling technologies usually produce plastic only good enough for clothing and carpets.

The company behind the breakthrough, Carbios, said it was aiming for industrial-scale recycling within five years. It has partnered with major companies including Pepsi and L’Oréal to accelerate development. Independent experts called the new enzyme a major advance.

 The work began with the screening of 100,000 micro-organisms for promising candidates, including the leaf compost bug, which was first discovered in 2012.

The scientists analysed the enzyme and introduced mutations to improve its ability to break down the PET plastic from which drinks bottles are made. They also made it stable at 72C, close to the perfect temperature for fast degradation.

The team used the optimised enzyme to break down a tonne of waste plastic bottles, which were 90% degraded within 10 hours. The scientists then used the material to create new food-grade plastic bottles.

Carbios has a deal with the biotechnology company Novozymes to produce the new enzyme at scale using fungi. It said the cost of the enzyme was just 4% of the cost of virgin plastic made from oil.

Waste bottles also have to be ground up and heated before the enzyme is added, so the recycled PET will be more expensive than virgin plastic. But Martin Stephan, the deputy chief executive at Carbios, said existing lower-quality recycled plastic sells at a premium due to a shortage of supply.

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