Scientists hope an engineered enzyme that eats plastic could usher in a recycling revolution – and it was found entirely by accident.
British researchers inadvertently created the plastic-digesting enzyme while conducting X-ray experiments on natural bacteria found in a Japanese recycling centre, causing it to mutate into a more powerful enzyme.
Tests showed that the lab-made mutant had a supercharged ability to break down polyethylene terephthalate (PET), one of the most popular forms of plastic employed by the food and drinks industry, and convert it into its original chemicals.
This could help reduce waste output and also tackle the use of crude oil in plastic manufacture.
Plastic bottles strewn over the shores of beaches and killing marine wildlife could soon be a thing of the past. British scientists have come up with a novel way of improving the recycling of the most common type of plastic waste using an enzyme
In most forms of existing recycling, plastic bottles are recycled into lower-quality materials and products, such as fleeces or carpets.
As a result, there are two qualities of PET – virgin grade and rPET (recycled).
Virgin grade is manufactured from crude oil and can be used to make high-quality products, including plastic bottles.
So far, there is no successful way of making high-end products from rPET.
Although it can be turned into other products, it is extremely hard to break down the polymers of PET (polyethylene terephthalate) into its base monomers.
Monomers are the individual chemicals which come together to form a polymer.
Research from scientists at the University of Portsmouth and the US Department of Energy’s National Renewable Energy Laboratory have found a way to resolve this problem.
Professor John McGeehan of Portsmouth said: ‘The key here is that we are recycling, but better.
‘When PET bottles are collected, they are not often turned back into plastic bottles. Current processes degrade the quality and manufactures prefer to use fresh ‘virgin PET’ from oil.
‘The recycled PET is less valuable and ends up as clothing, then carpet, then often landfill.
‘Our enzyme will break the plastic down to its original building blocks so that it can be reused and turned back into plastic. A real circular process’, he said.
PETase (pictured) was originally discovered at a plastics reprocessing plant in Japan. It has been found to feed off plastic. PET is the plastic used for food and drink packaging such as mineral water bottles
When recycling plastic bottles, they can only be turned into lower-quality objects. As a result, this means that to make more plastic bottles, they must be manufactured from crude oil
Scientists used specialist viewing technique called X-ray diffraction as well as scanning electron microscopy (SEM) to capture the details of the 3D structure
PETase is an enzyme that has been specifically engineered to break the plastic into its founding chemicals.
Enzymes are used throughout nature to break apart existing chemicals to transform them.
Often they create new products, but they can also allow the reclamation of the original parts.
The development of this enzyme means that recycled plastic can be made into top grade plastic again.
Scientists used a specialist viewing technique called X-ray diffraction to capture the details of PETase’s 3D structure.
PET plastic is used for food and drink packaging, especially for mineral water and ready meals.
PET plastic is the plastic used for food and drink packaging such as mineral water bottles. It is signified by the number ‘1’ in a triangle on bottles
The development of this enzyme means that recycled plastic can be made into top grade plastic again
It is signified by the number ‘1’ in a triangle on bottles.
The breakthrough was based on a chance discovery.
A type of bacteria, discovered at a plastics reprocessing plant in Japan, was found to be feeding off plastic.
As plastic has only existed for the past 80 years, the bacteria is thought to have evolved the ability to digest plastic in recent years.
The scientists used the enzyme in the Japanese plant as a base and then bio-engineered it to make it more effective.
Professor McGeehan added: ‘Few could have predicted that since plastics became popular in the 1960s huge plastic waste patches would be found floating in oceans, or washed up on once pristine beaches all over the world.
‘We can all play a significant part in dealing with the plastic problem, but the scientific community who ultimately created these ‘wonder-materials’, must now use all the technology at their disposal to develop real solutions.’
HOW DAMAGING ARE PLASTIC BOTTLES?
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.
Dr Oliver Jones, Reader of analytical chemistry at RMIT University in Melbourne, who was not involved in the research said: ‘I think this is very exciting work.
‘Enzymes are non-toxic, biodegradable and can be produced in large amounts by microorganisms (bacteria and fungi).
‘Although most people don’t know it, enzymes already help us out in many areas of everyday life such biological laundry detergents and in the food, leather, and textiles industries.
‘This very detailed paper shows that there is strong potential to use enzyme technology to help with society’s growing waste problem by breaking down some of the most commonly used plastics.
‘While there is still a way to go before you could recycle large amount of plastic with enzymes, and reducing the amount of plastic produced in the first place might, perhaps, be preferable, this is certainly a step in a positive direction and very exciting science to boot.’