New Enzyme Found Only in Compost Set Speed ​​Record to Break Down Plastic

Can take the plastic container that is dumped in the landfill hundreds of years to degrade naturally, but the newly discovered enzyme can devour waste in less than a day.

A highly efficient polyester hydrolase, known as PHL7, was recently found in a German cemetery fed through compost.

In the lab, researchers found that it was able to degrade polyethylene terephthalate (PET) by 90 percent within 16 hours.

PHL7 is not the first natural “plastic eater” that scientists have discovered, but it is the fastest.

In 2016, a PET-guzzling enzyme, called LLC, was found in a recycling plant in Japan. In the years that followed, it was advertised as a golden plastic shredder. But the newly discovered PHL7 is twice as fast in function.

Since 2016, the LLC enzyme has been modified by scientists to create a mutation more sinister than normal, but even this synthetic creature has a thing or two to learn from PHL7.

“The enzyme discovered in Leipzig could make an important contribution to the establishment of alternative energy-efficient 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 rapidly degrading used PET food packaging and suitable for use in an environmentally friendly recycling process where new plastics can be produced from the decomposition products.”

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

But if PHL7 is given a fruit tray made of PET plastic, it can break down the waste in less than 24 hours.

Even better, the byproducts of this recycling process can be reconstructed to create new plastic containers.

The possibilities for recycling are enormous. Every year, more than 82 million metric tons of PET is produced all over the world, and only a small percentage to new plastic.

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

On the other hand, biological recycling can help create a cheap and efficient circular plastic economy. Over the past few years, scholars have been Racing for development For this very purpose bacteria that feed on plastic.

PHL7 stands out from the other candidates found so far. The way PET disintegrates quickly appears to depend on a single building block in its DNA.

At a specific place in the amino acid sequence, PHL7 carries leucine where other enzymes carry a phenylalanine residue. In the past, leucine at this position has been linked to binding polymers to enzymes.

When researchers in Germany replaced phenylalanine with leucine in another enzyme, the organism became faster at breaking down plastic. In fact, its efficiency was on par with PHL7.

Compared with LLC enzymes, PHL7 enzyme was also able to bind to more polymers in vitro.

“These results suggest that the phenylalanine/lysine substitution could be partly responsible for the changes in the binding energy contributions of each residue in PHL7,” the authors Write.

Not only is PHL7 fast, this enzyme requires no pre-treatment before it burrows inside. It will eat plastic without grinding or melting.

The process of putting the by-products back together again does not have to depend on petrochemicals.

“So” the authors deduce“By using powerful enzymes such as PHL7, it is possible to directly post-consumer thermoplastic PET packaging in a closed-loop process with a low carbon footprint and without the use of petrochemicals, achieving a sustainable recycling process for important PET plastic waste streams.”

Given the dire state of plastic pollution around the world, this sounds like a dream. The team of researchers at the University of Leipzig is now working on a prototype.

The study was published in ChemSusChem.