Plastic-degrading enzyme the next hope for industrial-scale recycling?

21 Apr 2020 --- New research has established an improved hydrolase that can break down a minimum of 90 percent PET into monomers within just ten hours, with a productivity of 16.7 grams of terephthalate per liter per hour. The Toulouse Biotechnology Institute, France, researchers also demonstrated that biologically recycled PET – exhibiting the same properties as petrochemical PET – can be produced from enzymatically depolymerized PET waste before being processed into bottles. Carbios, a company trying to use the enzymes in industrial-scale recycling to produce food-grade plastics, made the discovery and is currently running this technology at the pilot stage.

“We are very proud of this finding. It clearly illustrates the power of the French public/private collaboration to drive fundamental and applied research to the highest international level,” co-author Sophie Duquesne from the Toulouse Biotechnology Institute, Bio & Chemical Engineering, tells PackagingInsights.

Duquesne further highlights that PET producers can use recycled monomers in their existing facilities to produce the equivalent of virgin PET plastics, which can then be used in any of its original applications, according to circular economy principles. “By keeping current PET polymerization facilities unchanged, the technology has the potential to be deployed globally and therefore become an industrial standard that is both competitive and eco-responsible.”

Moving their findings out of the lab over industry’s threshold, the research team came to an agreement with leading enzyme producers Novozymes, based in Denmark, to industrially produce this enzyme.

Revolutionizing plastic waste disposal
Duquesne and her colleagues’ “revolutionary process” uses a PET hydrolase enzyme that breaks down PET plastic waste into its original components, which can then be recombined into high quality PET plastic, equivalent to virgin PET. 

Click to EnlargeToulouse Biotechnology Institute developed a hydrolase enzyme to depolymerize PET waste and convert it into high-quality plastic.“Our depolymerization process is very tolerant of feedstock and doesn’t require pure PET feedstock. It works with clear, colored, opaque and even multilayered bottles and packaging products as well as polyester fibers. It is possible to recycle multilayers packaging containing polyamide or polyethylene in addition to PET. That is the case for most sparkling water bottles containing two internal layers of PET and one layer of polyamide to avoid CO2 leaking. At the end of the process of depolymerization said polyamide will be a final waste,” says Duquesne.

“This technology opens up a whole new class of feedstocks that until now were not recyclable by mechanical recycling. This means less plastic to landfill or incineration. Our technology is designed to be operated by PET producers. Instead of using fossil-based resources to produce virgin PET, they will be able to use plastic waste as their raw material to produce the equivalent of virgin PET,” she continues.

Real-world relevance
Carbios is attempting to use the enzymes in industrial-scale recycling to produce food-grade plastics. The company made the enzyme discovery and is currently piloting the technology.

“Carbios also launched the construction of an industrial demonstration plant, which will use this enzymatic depolymerization process from beginning 2021 to recycle post-consumer PET waste. The research is continued to design a new generation of further optimized enzymes and apply this technology and scale up to PET fibers,” Duquesne concludes.

The pioneering research comes not a minute too soon as the plastic pollution crisis continues to pile up. In similar research strides, a German research team recently discovered a bacterium that not only feeds on plastic but also produces energy from it to fuel the process. Polyurethane – which releases toxic chemicals that kill most bacteria – is attacked and broken down by the newly-discovered bacterium. One of the researchers describes the discovery as an “important step in being able to reuse hard-to-recycle polyurethane products.”

Plastic-ridden landfills cause concern to environmental protection agencies while FMCG companies are being called out on their corporate responsibility for plastic pollution.

By Anni Schleicher

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