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Leiden researchers have discovered an enzyme that helps bacteria feed on everyday plastics. This common enzyme could play a crucial role in future research and eventually in addressing the global plastic crisis. The study is in Nature Communications.

About 10 years ago, scientists discovered bacteria capable of breaking down plastics. This was a big deal. Until then, plastic was thought to be virtually indestructible in a natural environment and therefore likely to persist in nature for millions of years. Admittedly, the bacteria were quite slow and not very efficient at breaking plastics down. But the discovery turned out to be a starting point for researchers looking to speed up this natural process.

Some researchers focus on breaking down the plastic PET into its basic components using bacteria. PET is commonly used to produce drinking bottles and food containers. Others look at the next step in the process, where these PET components are converted into products that can actually be used to make new materials. Again, with the help of bacteria.

This is where the research of Lennart Schada von Borzyskowski, microbiologist at the Institute of Biology Leiden (IBL), comes in. His team examined how a bacterium called Paracoccus denitrificans can use ethylene glycol to grow. Ethylene glycol is one of the components derived from PET plastic. Schada von Borzyskowski specifically focused on the role of enzymes in this process. These are proteins that speed up chemical reactions in living organisms.

Process is similar to how our body converts alcohol

An analogy helps to understand how this process works. Most people are familiar with ethanol, the alcohol found in beer and wine. When you drink a beer, the body identifies the ethanol as toxic and converts it into less harmful chemicals. This is done by enzymes. Each enzyme is supported by a so-called cofactor, sometimes referred to as a "helper molecule."

In a similar way, bacteria can "consume" ethylene glycol, using enzymes and their cofactors. To demonstrate this, the researchers at the IBL added the bacterium to ethylene glycol to observe its response. And indeed, "the bacteria grew quite nicely," Schada von Borzyskowski says.

One of the main findings was that Paracoccus denitrificans was able to do this using enzymes with a very common cofactor. "Previously, other enzymes have been studied, but they only worked with a cofactor that was quite rare," the researcher explains. A cofactor that is widely available obviously makes the whole process easier.

Converting plastics into any molecule you might need

This discovery opens up possibilities for future research. According to Schada von Borzyskowski, this enzyme is likely present in many other bacteria as well. "This allows us to reevaluate all the bacteria that are out there," he says. While Paracoccus denitrificans proved useful in this study, other bacteria may still be much better at converting ethylene glycol.

Schada von Borzyskowski calls the discovery "a blueprint or a stepping stone" for future work. "Theoretically, you can produce any molecule you want from a plastic component such as ethylene glycol," he says. "As long as you can genetically engineer the bacteria to do this." He emphasizes that his research only examined what bacteria do "naturally," but the theoretical possibilities are endless.

For example, researchers in Scotland recently managed to turn PET components into paracetamol using a common bacterium that they engineered. This shows that future applications of this technique are promising, especially considering the growing problem of plastic pollution and the global push for a circular economy.