Pollution

A super PET-eating enzyme could become a key ally in tackling plastic pollution

Molecules that eat up plastic waste, including PET bottles, may soon become widely used as scientists leap ahead in developing new super enzymes.

There is hope that used plastic bottles could be eliminated by a super enzyme that “eats them up”. Enzymes are biological molecules, typically proteins, that significantly speed up the rate of virtually all the chemical reactions that take place within cells. They’re vital for life and serve a wide range of important functions. New research conducted by an international team, spurred by the discovery of the first bacterium that had naturally evolved to eat plastic at a waste dump in Japan in 2016, has significantly improved the enzyme’s ability to break down PET (polyethylene terephthalate), a type of plastic often used for drink bottles.

Plastic bottles on the side of the road in Kampala
Used plastic bottles on the side of the road in Kampala, Uganda © Godfrey Olukya

Plastic bottles, the scale of the problem

Over time, plastic bottles have been replacing glass ones because of their lower cost. Modern society has become addicted to them. But the manner in which they’re disposed of in most countries doesn’t only leave a lot to be desired but is also the cause of environmental disaster. Single-use packaging of soda, water and other drinks leads to mountains of garbage heaping up in legal and illegal dumpsites.

This has come at a cost. Over 80 per cent of used plastic bottles end up in landfills as well as lakes, rivers, seas and oceans. Scientists tell us that this waste leaks harmful chemicals into the environment as is slowly decomposes, causing a variety of health issues for humans who come into contact with these toxins, including reproductive problems and cancer.

They’re also deadly for wildlife. Many marine organisms get physically entangled in plastic trash and either drown or slowly starve to death. Others eat the plastics, mistaking the ubiquitous materials for food. Even large animals such as whales have been found to have perished after swallowing plastic bottles and other such materials.

Dump full of plastic items on the outskirts of Kampala, Uganda © Godfrey Olukya

A plastic-eating enzyme 

“Scientists have created a mutant enzyme that breaks down plastic drinks bottles – by accident,” by tweaking the enzyme initially discovered in Japan reported The Guardian on the 16th of April 2018. “The breakthrough could help solve the global plastic pollution crisis by enabling for the first time the full recycling of bottles’’. At the time, professor John McGeehan at the University of Portsmouth in the UK, who led the research, said: “What actually turned out was we improved the enzyme, which was a bit of a shock. It’s great and a real finding”.

Two years later, an even more effective enzyme has been created. The research was led by two teams, one at the University of Portsmouth and the other at the National Renewable Energy Laboratory in the US, and brought together the enzyme they had developed together with a second type. “Our first experiments showed that they did indeed work better together, so we decided to try to physically link them,” McGeehan, who is also director of the University of Portsmouth’s Centre for Enzyme Innovation said. The study was a huge team effort and “makes the possibility of true industrial-scale biological recycling of PET a possibility. This is a very large advance in terms of speed, efficiency and heat tolerance,’’ McGeehan pointed out.

Science magazine Popular Mechanics highlights how the new cocktail of bacteria eats plastic six times faster than methods that are currently used, as scientists introduced mutations to improve the enzymes’ ability to break down PET into intermediate and then elementary parts.

More than just an experiment

In April, French company Carbios announced that it had created another, separate enzyme, and that it is aiming for industrial-scale recycling within five years, by 2025. It has partnered with major companies, among them soft drinks manufacturer Pepsi, to accelerate the process. “It is absolutely a good development,” according to Hans Joergen Rasmussen, environmentalist and founder of the World Climate School, based in Norway. “Plastic bottles are a huge source of pollution. In my view getting rid of plastics is almost as important as transitioning to clean energy”.

In Africa, Jacob Tivenga, director of the Zimbabwe Environment and Climate Change Trust, said in an interview that “used plastic is a menace in Africa since it isn’t easy to recycle. Here in Zimbabwe even the government has failed to address the problem. City authorities are failing to collect and destroy waste. We hope that new developments can soon reach us here so that it helps us in destroying used plastic bottles”. While incorrect disposal of bottles and other items has become disastrous in most countries, a number of scientific efforts may open the door for reducing plastic pollution, without substituting, however, for more sustainable production and consumption patterns.

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