TAGS: Sustainability / Natural Solutions Additives for Packaging
A team from the University of Greifswald, together with Covestro and teams from Leipzig and Ireland, develop two new processes where enzymes as biocatalysts can degrade polyurethane and polyvinyl alcohol under mild conditions.
This created the basis for recycling both plastics in a resource-saving manner and developing environmentally friendly processes for their recycling to reduce the global problem of plastic waste for these two synthetic polymers, which are industrially produced in large quantities.
Environmentally Friendly Recycling of Plastics
Plastics are currently still indispensable to produce building materials, electrical insulation, beverage and food packaging, textiles and many other applications. Unfortunately, the mass production of plastic, especially for packaging, has led to enormous plastic pollution of our environment worldwide. The two plastics polyurethane and polyvinyl alcohol account for around eight percent of plastics production in Europe. For several years, intensive research has been carried out into methods that enable environmentally friendly recycling of plastics.
This would not only relieve the burden on the environment, but less crude oil would be required to produce plastic again. In addition, there would be significantly less greenhouse gas CO
2 are emitted because there is no need to incinerate the plastic waste in waste incineration plants.
Polyurethanes (PUR) are used in the manufacture of mattresses, insulating materials, thermoplastics (e.g. for sports shoes) and for coatings (sealants, paints and adhesives). For these substances, there are already basic chemical processes to break them down.
However, they require a considerable amount of energy since high temperatures and pressures are required. Biotechnological processes using microorganisms or enzymes as natural biocatalysts are an alternative, as they break down the plastic molecules at moderate temperatures of up to approx. 40 °C and without the use of chemical reagents and, above all, recycling, i.e., the extraction of the building blocks to produce new plastics make possible.
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Breaking Down PU Into Their Building Blocks
The team of Prof. Dr. Uwe Bornscheuer from the Institute of Biochemistry at the University of Greifswald, together with scientists from Covestro in Leverkusen, has now identified exactly the enzymes that, after chemical pretreatment, are able to break down polyurethanes into their building blocks.
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The search for these special biocatalysts was very time-consuming and we had to screen around two million candidates to find the first three enzymes that are proven to be able to break the special bond in polyurethane," describes doctoral student Yannick Branson (University of Greifswald ) the challenge of this project. "
With this groundbreaking discovery, we have now laid the foundation for further improving these biocatalysts using protein engineering methods, in order to be able to tailor them for industrial recycling of polyurethane,” says Prof. Dr. Uwe Bornscheuer (University of Greifswald) continues.
Polyvinyl alcohols (PVA) have versatile properties and are also widely used, e.g., in the coating of fibers and as films for packaging. So far, there have also been no mature processes for the degradation of PVA. Here, the researchers led by Professor Bornscheuer, together with a polymer expert from University College Dublin (Ireland) and scientists from Leipzig, were also able to develop the basis for a biotechnological process. The breakdown of PVA was achieved here by a clever combination of three different enzymes, which gradually change the polymer until fragments are formed that can be used as a material.
Although the findings that have now been published represent an important breakthrough, it will probably take a few more years before an industrial process is mature that will enable large-scale recycling of this plastic waste.
Source: University of Greifswald