A super enzyme that degrades plastic bottles six times faster than before was created by scientists and could be used for recycling within a year or two.
The research was published in the journal Proceedings of the National Academy of Sciences of the United States of America.
Enzyme that degrades plastic
In 2018, a group of Japanese scientists managed to isolate the enzyme responsible for breaking down PET into Ideonella sakaiensis, a bacterium with the ability to “eat plastic“.
This micro-organism, found in 2016 in landfills, has evolved over the years by adapting its diet to plastic waste.
The process of bacterial digestion represents an enormous discovery, but is extremely slow for practical purposes. This is why research in the sector is trying to accelerate it.
Scientists have redesigned and engineered PETase, the plastic-eating bacterial enzyme, to speed up the chemical recycling of polyethylene terephthalate.
The super enzyme
A team of scientists from the University of Portsmouth, England, in collaboration with the US NREL, has created an enzyme cocktail for the deconstruction of polyethylene terephthalate (PET), one of the most popular polymers in plastic packaging.
The Portsmouth group already had its hands on the enzyme in question – PETase – and was able to make its work of degrading plastic up to 20% faster.
The team, led by Professor John McGeehan and Dr Gregg Beckham, managed to push the speed bar even further.
How? By designing a molecule composed of PETase and a second bacterial enzyme called MHETase.
While natural deterioration can take hundreds of years, the super enzyme is capable of reconverting plastic in just a few days; researchers believe that combining it with enzymes that break down cotton could also allow mixed fabric garments to be recycled.
Results
Scientists have achieved this by first studying the atomic structure of enzymes with a synchrotron that uses X-ray beams 10 billion times brighter than the Sun.
This device acts as a microscope, allowing them to “focus” the 3D structure and use these insights to design the connections between the two enzymes.
The simple combination of PETase and MHETase has doubled the degradation rate of the plastic, but the engineering of special connections between the two molecules has produced a real super enzyme, increasing the decomposition rate by another three times.
Just like its predecessors, the new super enzyme digests PET plastic, returning the original constituent elements. But it does so six times faster.
The technique could be used as part of an endless chemical recycling cycle and open the door to decomposition of polymers other than PET.
A French company Carbios had revealed a different enzyme that degrades 90% of plastic bottles within 10 hours, but requires heating above 70°C.
The new super enzyme works at room temperature.