Scientists have been inspired by Pacman to create a plastic-eating ‘cocktail’, which could help eradicate plastic waste.
It’s made up of two enzymes – called PETase and MHETase – produced by a type of bacteria that feeds on plastic bottles, called Ideonella sakaiensis.
Unlike natural degradation, which can take hundreds of years, the super-enzyme is able to convert the plastic back to its original ‘building blocks’ in a few days.
The two enzymes work together like ‘two Pac-men joined by a piece of string’ munching down snack pellets in the popular video game.
The new super-enzyme digests plastic up to six times faster than the original PETase enzyme alone, which was discovered by the team in 2018.
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A model of the cocktail consisting of the MHETase and PETase enzyme (red and blue, respectively)
It targets polyethylene terephthalate (PET), the most common thermoplastic, which is used to make single-use drinks bottles, clothing and carpets and usually takes hundreds of years to break down in the environment.
‘Currently, we get those building blocks from fossil resources such as oil and gas, which is really unsustainable,’ Professor John McGeehan at the University of Portsmouth told PA news agency.
‘But if we can add enzymes to the waste plastic, we can start to break it down in a matter of days.’
In 2018, Professor McGeehan and his team accidentally discovered that an engineered version of one of the enzymes, known as PETase, was able to break down plastic in mere days.
For their new study, the team mixed PETase with the second enzyme, called MHETase, and found ‘the digestion of the plastic bottles literally doubled’.
British scientists have come up with a novel way of improving the recycling of the most common type of plastic waste using enzymes
The researchers then connected the two enzymes together in the lab, like ‘two Pac-men joined by a piece of string’, using genetic engineering.
‘PETase attacks the surface of the plastics and MHETase chops things up further, so it seemed natural to see if we could use them together, mimicking what happens in nature,’ said Professor McGeehan.
‘Our first experiments showed that they did indeed work better together, so we decided to try to physically link them.
‘It took a great deal of work on both sides of the Atlantic, but it was worth the effort – we were delighted to see that our new chimeric enzyme is up to three times faster than the naturally evolved separate enzymes, opening new avenues for further improvements.’
Professor McGeehan also used the Diamond Light Source, a synchrotron in Oxfordshire that uses intense beams of X-rays 10 billion times brighter than the Sun to act as a microscope powerful enough to see individual atoms.
This allowed the team to determine the 3D structure of the MHETase enzyme, giving them the molecular blueprints to begin engineering a faster enzyme system.
Academics used the powerful x-ray machine, The Diamond Light Source (pictured) in Oxfordshire to map 3D structures of the enzymes
Tests also showed that this super-enzyme was able to break down PET, which is also used in soft drinks and fruit juice packaging.
Although it is said to be highly recyclable, discarded PET persists for hundreds of years in the environment before it degrades.
Aside from PET, the super-enzyme also works on PEF (polyethylene furanoate), a sugar-based bioplastic used in beer bottles, although it’s unable to break down other types of plastic.
The team are now looking at ways to even further speed up the break-down process, so the technology can be used for commercial purposes.
‘The faster we can make the enzymes, the quicker we can break down the plastic, and the more commercially viable it will be,’ Professor McGeehan told PA.
The study has been published in the journal Proceedings of the National Academy of Sciences of the United States of America.
Eight million tonnes of plastics find their way into the ocean every year
Of 30 billion plastic bottles used by UK households each year, only 57 per cent are currently recycled.
With half of these going to landfill, half of all plastic bottles that are recycled go to waste.
Around 700,000 plastic bottles a day end up as litter.
This is largely due to plastic wrapping around bottles that are non-recyclable.
Bottles are a major contributor to the increasing amount of plastic waste in the world’s oceans.
Researchers warned eight million tonnes of plastics currently find their way into the ocean every year – the equivalent of one truckload every minute.
The amount of plastic rubbish in the world’s oceans will outweigh fish by 2050 unless the world takes drastic action to further recycle, a report released in 2016 revealed.
At current rates, this will worsen to four truckloads per minute in 2050 and outstrip native life to become the largest mass inhabiting the oceans.
An overwhelming 95 per cent of plastic packaging – worth £65 – £92billion – is lost to the economy after a single use, the Ellen MacArthur Foundation report stated.
And available research estimates that there are more than 150 million tonnes of plastics in the ocean today.
Plastic pollution is ruining the ecosystems of the world, both marine and terrestrial. It litters shorelines, snags animals and suffocates entire populations of animals
So much plastic is dumped into the sea each year that it would fill five carrier bags for every foot of coastline on the planet, scientists have warned.
More than half of the plastic waste that flows into the oceans comes from just five countries: China, Indonesia, Philippines, Vietnam and Sri Lanka.
The only industrialized western country on the list of top 20 plastic polluters is the United States at No. 20.
The US and Europe are not mismanaging their collected waste, so the plastic trash coming from those countries is due to litter, researchers said.
While China is responsible for 2.4 million tons of plastic that makes its way into the ocean, nearly 28 percent of the world total, the United States contributes just 77,000 tons, which is less than one percent, according to the study published in the journal Science.