A new enzyme found in compost sets a record for the rate at which plastic breaks down

(ORDO NEWS) — A plastic container thrown into a landfill can take hundreds of years before it naturally breaks down, but a newly discovered enzyme can devour the waste in less than a day.

A highly effective polyester hydrolase known as PHL7 was recently discovered in a German cemetery while chewing on compost.

Researchers in the laboratory found that it was able to degrade polyethylene terephthalate (PET) by 90 percent within 16 hours.

PHL7 isn’t the first natural plastic eater scientists have discovered, but it’s the fastest.

In 2016, a PET-eating enzyme called LLC was discovered at a waste recycling plant in Japan. It has since been hailed as the gold standard for plastic shredders. But the newly discovered PHL7 works twice as fast.

Since 2016, scientists have modified the LLC enzyme to create an even more voracious mutant than the natural one, but even this synthetic creation has a lot to learn from PHL7.

“The enzyme discovered in Leipzig could make an important contribution to the creation of alternative energy-saving plastic recycling processes,” says microbiologist Wolfgang Zimmermann from the University of Leipzig in Germany.

“The biocatalyst, now developed in Leipzig, has been shown to be highly effective in the rapid degradation of used PET food packaging and is suitable for use in an environmentally friendly recycling process in which new plastic can be obtained from the degradation products.”

Unfortunately, neither PHL7 nor LCC can completely degrade higher crystallinity (more organized molecular structure) PET plastics such as those used in some bottles.

But if PHL7 is given a PET plastic fruit basket, it can recycle waste in less than 24 hours.

What’s more, the by-products of this recycling process can be used to create new plastic containers.

The possibilities for recycling are enormous. More than 82 million metric tons of PET are produced each year worldwide, and only a small percentage is recycled into new plastic.

Even when a plastic product is sent to a recycling plant, the process of melting it down and creating something new is energy-intensive and expensive.

On the other hand, bio-recycling can help create a cheap and efficient zero-waste plastic economy. Over the past few years, scientists have sought to develop plastic-eating bacteria for this very purpose.

PHL7 stands out from other candidates found so far. How quickly it breaks down PET seems to depend on one building block in its DNA.

At a certain point in the amino acid sequence, PHL7 carries a leucine, while other enzymes carry a phenylalanine residue. In the past, leucine at this position has been associated with the binding of polymers to enzymes.

When researchers in Germany replaced phenylalanine with leucine in another enzyme, the body broke down plastic much faster. In fact, its efficiency was on par with PHL7.

Compared to the LLC enzymes, the PHL7 enzyme was also able to bind to more polymers in the lab.

“These results indicate that the phenylalanine/leucine substitution may be partly responsible for the changes in the binding energy contribution of each residue in PHL7,” the authors write.

PHL7 is not only fast, this enzyme does not require any pre-treatment. before he burrows. It will eat plastic without grinding or melting.

The process of recombining by-products should also not depend on petrochemicals.

“Thus,” the authors conclude, “the use of powerful enzymes such as PHL7 allows direct recycling of pre-owned thermoformed PET packaging in a low-carbon, petrochemical-free closed loop, realizing a sustainable recycling process for an important stream. PET plastic waste.

Considering the terrible state of plastic pollution around the world, this sounds like a dream come true. A team of researchers from the University of Leipzig is currently working on a prototype.


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