Scientists develop ‘super enzyme’ that breaks down plastic faster than ever

“The enzymes are really specific to certain types of bonds in the molecular structure of the plastic. This means that it breaks it down into the same starting materials that were used to make the product to begin with,” Erika Erickson, a bioengineering researcher at the U.S. Department of Energy’s National Renewable Energy Laboratory (NERL), told As It Happens host Carol Off. 

“So instead of having an inferior product in the end, you could start with the same starting materials and come back to an equal value plastic water bottle or food package, etc., on the other side, without needing to use petroleum products to get there.”

The findings were published this week in the journal Proceedings of the National Academy of Sciences.

Nature finds a way — and scientists speed it up 

The whole thing began when scientists at NERL and Britain’s University of Portsmouth discovered a naturally occurring enzyme in a waste recycling centre in Japan that was helping bacteria break down polyethylene terephthalate (PET), a common plastic developed in the ’40s that’s used to make water bottles, food packaging, film and more. 

“There are natural enzymes that have been evolved to break down plastic,” Erickson said. “And if you think about that, it’s quite extraordinary that an organism has been able to do this in such a short amount of time.”

However, the natural process is a slow one. So the scientists tweaked the enzyme by adding amino acids to speed things up.

The resulting engineered enzyme, called PETase, could break down one water bottle in a couple months, Erickson estimated — a big step up from the hundreds of years it takes to break down in nature.

Now the team has combined PETase with a second enzyme from the same garbage eating bacteria, called MHETase, making the process even faster. The new super enzyme, Erickson said, could potentially break down one bottle in as little as six weeks. 

She admits that’s still “a little bit too slow for a real recycling process,” but says it’s a major step forward to creating a commercially viable system. 

The way plastic is recycled now is not very efficient or cost-effective, says Erickson.

“In mechanical recycling, the plastic gets ground down into small pieces and then melted and then reformed into a new product,” she said.

“But in the process of doing that, all of the contaminated dirt or food products or other types of plastic get mixed into that. So the quality of the recycled good is usually quite low compared to the original.”

With an enzymatic approach, however, the plastic is recycled in its entirety — turning a bottle, for example, back into the same material used to make the bottle, and potentially creating an infinite loop of recycling.

Another big problem with modern recycling is the amount of energy used to collect materials and deliver them to a central location for sorting. 

“That won’t necessarily be a problem that disappears with a new strategy for recycling,” Erickson said.

“The difference, however, would be that the embedded use of fossil fuels for the extraction of petroleum from the Earth, you would lose a lot of that, which is also quite costly…. If we could separate some of the products that we use from that cycle, then the greenhouse gas emissions and fossil fuel utilization would be lower.”

Technology helps — but people have to step up 

The team has touted the potential of this method to one day revolutionize recycling, should it be developed on a commercial scale. 

But Erickson notes that technology alone won’t fix the problem of plastic pollution.

“It’s difficult to convey the ability to sort of shirk off responsibility for our daily choices toward this kind of technology in general … each of us can make a difference in our daily choices,” she said.

“And so I hope that people both understand that [with this] technology, we’re hoping we can we can make some big impacts and in good directions, but it still comes down to individual choices.”

Written by Sheena Goodyear. Interview produced by Menaka Raman-Wilms and Kate Cornick.