Plastic-Eating Enzyme May Be Our Planet's New Hope


Artist's rendering of the PET-eating enzyme attached to a plastic molecule. Screen shot from YouTube/HowStuffWorks/Diamond Light Source

One of the amazing things about our universe is that nothing really goes to waste. For instance, you — the incredible masterwork that you are — happen to be composed of the trash that exploded out of a supernova. In every nook and cranny of the cosmos, the universe is reorganizing and reusing. It is The Great Recycler.

This planet recycles everything — water, carbon, nutrients of all kinds. So, it stands to reason that we'd be really good at recycling stuff here on Earth. But we humans are only so-so recyclers. Take plastic: We do a great job of digging up ancient deposits of carbon in order to make the stuff — recycling, sort of! — but since the 1940s, we've manufactured mind-boggling amounts of a material that will likely hang out in the environment for centuries, killing wildlife and leaching toxic chemicals. Only about 10 percent of that is ever recycled.

But in 2016, a Japanese research team discovered bacteria making some inroads into plastics recycling where humans were failing. Polyethylene terephthalate (PET) plastics are everywhere — most notably in plastic soda and water bottles — and the bonds that hold it together are very strong, so it was something of a surprise when a colony of these bacteria were discovered in a Japanese landfill. But what's their secret?

In the April 17, 2018 issue of Proceedings of the National Academy of Sciences journal, an international group of researchers reported on the PET-busting enzyme produced by this bacteria. Not only did they map the structure of the enzyme, in the process of studying and tinkering with it, they also made it faster. Turns out, it was all a bit of an accident.

"We hoped to determine its structure to aid in protein engineering, but we ended up going a step further and accidentally engineered an enzyme with improved performance at breaking down these plastics," said lead author Gregg Beckham, senior engineer at the National Renewable Energy Laboratory, in a press release. "What we've learned is that PETase is not yet fully optimized to degrade PET — and now that we've shown this, it's time to apply the tools of protein engineering and evolution to continue to improve it."

The goal of this research is to find a way to create an enzyme fast enough to break down huge amounts of PET plastic into its component parts so it can be turned back into plastic bottles. One possible solution is to plant this mutant enzyme into bacteria that can withstand insanely high temperatures, which might break the plastic down 10 to 100 times quicker.

Whatever it takes, guys.


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