Scientists have developed an enzyme that can break down plastic bottles — and the creation was a happy accident.
An international team of researchers made the discovery while studying a natural enzyme that was believed to have evolved to eat plastic in a waste recycling center in Japan.
The researchers modified the enzyme to analyze its structure, but instead accidentally engineered an enzyme that was even better at breaking down the plastic used for soft drink bottles, polyethylene terephthalate or PET.
"Serendipity often plays a significant role in fundamental scientific research and our discovery here is no exception," said lead researcher, professor John McGeehan of the University of Portsmouth in the U.K., in a statement.
"Although the improvement is modest, this unanticipated discovery suggests that there is room to further improve these enzymes, moving us closer to a recycling solution for the ever-growing mountain of discarded plastics."
The new enzyme starts breaking down the plastic in just a few days. But the researchers are working to improve the enzyme so it breaks down plastics even more quickly. They say the discovery could offer a solution for millions of tons of plastic bottles made of PET that linger in the environment. Plastic takes more than 400 years to degrade.
The plastic problem
One million plastic bottles are bought around the world every minute, and the number will likely increase by another 20 percent by 2021, reports The Guardian, citing statistics from consumer market research company Euromonitor International.
Of the 8.3 million metric tons of plastic that have been produced so far, a mere 9 percent of it has been recycled, researchers in a 2017 study estimated. The vast majority of it — 79 percent — is sitting in landfills or in the environment, much of it floating in our oceans. "If current production and waste management trends continue, roughly 12 [billion metric tons] of plastic waste will be in landfills or in the natural environment by 2050," said the researchers.
"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," McGeehan said.
"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."
The story behind the discovery
The new research, published in the journal Proceedings of the National Academy of Sciences, began with investigators working to figure out the exact structure of the enzyme that evolved in Japan. Researchers collaborated with scientists at the Diamond Light Source synchrotron science facility, using an intense beam of X-rays that is 10 billion times brighter than the sun and acts like a microscope to reveal individual atoms.
The team found that the enzyme looked similar to one that breaks down cutin, a waxy, protective coating for plants. When they mutated the enzyme to study it, they accidentally improved its ability to eat PET plastic.
"The engineering process is much the same as for enzymes currently being used in bio-washing detergents and in the manufacture of biofuels — the technology exists and it’s well within the possibility that in the coming years we will see an industrially viable process to turn PET and potentially other substrates ... back into their original building blocks so that they can be sustainably recycled," McGeehan said.