Plastic waste: Modified enzyme recycles plastic

Bags, bottles, packaging: plastic is everywhere, but disposal is difficult. With mechanical recycling, the quality of the plastic decreases. Chemical recycling is not very common yet. The French company Carbios may have found a solution to the problem: an enzyme that breaks down plastic.

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  1. Fraunhofer Institute for Factory Operation and Automation IFF, Magdeburg
  2. BWI GmbH, throughout Germany

The enzyme is said to be used to recycle the plastic polyethylene terephthalate (PET). The enzyme breaks down PET into its two building blocks, terephthalic acid and ethylene glycol. The team headed by Alain Marty, Scientific Director of Carbios, and Isabelle André from the University of Toulouse showed that the enzyme is able to break 90 percent of 90 grams of PET in 90 hours. The scientists were then able to create new PET from the two components. The plastic bottles made from it are just as stable as those from conventional PET, the researchers write in the journal Nature.

Japanese researchers discovered the enzyme called LCC (from Leaf-Branch Compost Cutinase) in 2012 on a compost heap. It breaks up the waxy layer that protects the leaves of many plants. However, the original enzyme worked very slowly and disintegrated after a few days at 65 degrees Celsius. This is the temperature at which PET softens, which makes it easier for the enzyme to get into the polymer.

The enzyme LCC was already forgotten

At the beginning of their project, Marty and André tested a large number of microorganisms as to whether they were suitable for the biological recycling of plastics. They also came across LCC. The enzyme had already been forgotten, Marty told The Guardian. But it turned out to be the best.

The team then experimented with amino acids to change the enzyme. On the one hand, the researchers achieved that the enzyme is stable even at 72 degrees – the temperature at which PET melts – and does not disintegrate like the original. On the other hand, the modified enzyme is 10,000 times more efficient.

The use of LCC in recycling could have several advantages: For example, the plastic bottles do not have to be sorted: For mechanical recycling, plastic must be separated according to type and color. That doesn't apply. The enzyme ignores colors and other plastics, John McGeehan told Science magazine. He is the director of the Center for Enzyme Innovation at the University of Portsmouth and was not involved in the project. "It is an important step forward."

Carbios plans to launch the enzyme as a product. The company is cooperating with this the Danish biotechnology company Novozymesthat the enzyme is said to produce in large quantities with the help of mushrooms. "We are the first company to bring this technology to the market"said Martin Stephan, deputy chief of Carbios, the Guardian. "Our goal is to be ready for use on an industrial scale by 2024, 2025".

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