Newly discovered enzyme breaks down PET plastic in record time – SWR Knowledge

Plastic Bottles, Fruit Bowls, and Chips: These lightweight PET plastic packages become a problem if they are not recycled. Scientists from the University of Leipzig have now discovered a highly efficient enzyme that breaks down PET in record time.

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Decomposition by enzymes is more sustainable than recycling

Biochemist Christian Sonnendecker explains that Leipzig’s research team has found an enzyme that degrades PET at an astonishingly fast rate, so that an economically viable implementation is within reach.

It has been known for some time that certain enzymes, called polyester splitting hydrolysates, can also break down PET. But so far, the process of decomposing plastic has taken a long time to be of commercial use.

Here we now have a filter with which we can, for example, completely disassemble a PET package from the supermarket in less than a day. And for the first time, this is the reaction time where we can also consider direct PET, without the need for treatment in a decomposition reactor.

Some enzymes can quickly break down PET into their individual components.

press office

Christian Sonnedecker / University of Leipzig

Super enzymes on compost piles in the Leipzig cemetery

Researchers have discovered the ultrafast plastic-splitting enzyme in a compost heap at the Leipzig cemetery. Not surprisingly, compost piles are the perfect digging site for enzyme searches, because enzymes break down plant polymers in nature. According to Sonnendecker, microorganisms that use enzymes are known to be found primarily in leaf compost piles.

How is PET broken down using enzymes (model) (Photo: press office, Christian Sonnedecker/Uni Leipzig)

This is how PET enzyme analysis works (model).

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Christian Sonnedecker / University of Leipzig

Enzymes must be heat stable

Compost can easily reach 60 to 70 degrees indoors due to the fermentation process. This is exactly what scientists use and drill at least 50 to 70 cm deep for their samples: they are looking for enzymes that are highly heat-stable. The more stability the better, says Christian Zönendecker.

High temperatures can occur in the compost heap due to decomposition processes.  (Photo: Imago Images, Imago / Panther Media / Martina Berg)

High temperatures can occur in the compost heap due to decomposition processes.

imago pictures

imago / panthermedia / martina berg

Decomposition occurs optimally at temperatures between 60 and 70 degrees. Natural enzymes cannot withstand this temperature. So researchers from Leipzig looked for heat-stable versions of these enzymes.

This is when the real work begins, explains Christian Sonnedecker, a biochemist in Leipzig. This is because the candidate enzymes must be obtained and purified in a laborious process. Only then are they tested in small jars to see how well they degrade the plastic.

Biochemist Christian Zunendecker has discovered some enzymes in a cemetery's compost heap that can break down PET plastic.  (Photo: press office, Sven Reichold/Uni Leipzig)

Biochemist Christian Zunendecker has discovered some enzymes in a cemetery’s compost heap that can break down PET plastic.

press office

Sven Reichold / University of Leipzig

Enzymes break down PET into its building blocks

PET plastic does not simply degrade, but rather degrades into basic building blocks. This can then be processed again and used to produce new PET plastic. This could create a cycle in which no new crude oil is needed to produce PET.

We can now take this material, break it down into its building blocks, and make a new PET material again, of the highest quality. Traditional mechanical processes mean that quality decreases with each recycling step.

In the so-called bottom cycle, the PET bottle later becomes fruit packaging, and in the last step, textiles or carpets that can no longer be used and burned.

Extensive testing facility planned

Scientists hope to escape this downward spiral by using a new enzyme that speeds up PET degradation. In the next step, they want to set up a testing facility to see how the process can be implemented on a larger scale.

In a few years, researchers hope to have an alternative way to keep PET in a closed cycle. This could set new standards when it comes to sustainability.

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