Scientists have accidentally hit a breakthrough in recycling by creating mutant enzymes that eat plastic bottles.
These mutant enzymes enable the possibility of solving the global plastic pollution crisis by creating for the first time, a full recycling process of plastic. The new study derives from a discovery in 2016 of the first bacterium that had naturally evolved to eat plastic at a waste dump in Japan.
The new research published in the journal, Proceedings of the National Academy of Sciences, began by determining the precise structure of the enzyme produced by the Japanese bug. The scientists used an intense beam of x-rays that is 10bn times brighter than the sun, to reveal individual atoms.
The structure of the enzyme is similar to bacteria that can break down cutin—a natural polymer used as a protective coating by plants. When the research team manipulated the enzyme to explore this connection, they ended up accidentally improving its ability to eat PET (polyethylene terephthalate).
The new mutant enzymes only take a few days to start breaking down the plastic, which is much faster than the centuries it usually takes in the ocean. Researchers are optimistic that they can speed this process up even faster.
“What we are hoping to do is use this enzyme to turn this plastic back into its original components, so we can literally recycle it back to plastic,” said Professor John McGeehan, at the University of Portsmouth, UK, who led the research. “It means we won’t need to dig up any more oil and, fundamentally, it should reduce the amount of plastic in the environment.”
The current recycling process only makes up of 14% of the over 1 million plastic bottles that are sold each minute around the world. This leaves billions of plastic bottles attempting to degrade in oceans, harming marine life and potentially humans at the same time.
What makes matters even worse, is that currently the 14% that is recycled, can only be turned into opaque fibers for clothing or carpets. This new enzyme will hopefully have the ability to recycle plastic bottles back into plastic bottles for use.
The researchers have big plans for these enzymes. A possible future study would involve the exploration of the ability to transplant the mutant enzyme into an extremophile bacterium that could survive temperatures above 70°C, at which point PET changes from a glassy to a viscous state, making it likely to degrade 10-100 times faster.
“I think [the new research] is very exciting work, showing there is strong potential to use enzyme technology to help with society’s growing waste problem,” said Oliver Jones, a chemist at RMIT University in Melbourne, Australia, and not part of the research team.
“Enzymes are non-toxic, biodegradable and can be produced in large amounts by microorganisms,” he said. “There is still a way to go before you could recycle large amounts of plastic with enzymes, and reducing the amount of plastic produced in the first place might, perhaps, be preferable. [But] this is certainly a step in a positive direction.”
Interested in the full study? Check it out here: http://www.pnas.org/