Thu, Mar 17, 2016 - Page 9 News List

Nature fights back with plastic-eating bacteria

Scientists have discovered a species of bacteria capable of breaking down commonly used PET plastic, but remain unsure of its potential applications

By Karl Mathiesen  /  The Guardian

Illustration: Mountain People

Nature has begun to fight back against the vast piles of filth dumped into its soils, rivers and oceans by evolving a plastic-eating bacteria — the first known to science.

In a report published in the journal Science, a team of Japanese researchers described a species of bacteria that can break the molecular bonds of one of the world’s most-used plastics — polyethylene terephthalate, also known as PET or polyester.

The Japanese research team sifted through hundreds of samples of PET pollution before finding a colony of organisms using the plastic as a food source.

Further tests found the bacteria almost completely degraded low-quality plastic within six weeks. This was voracious when compared with other biological agents; including a related bacteria, leaf compost and a fungus enzyme recently found to have an appetite for PET.

“This is the first rigorous study — it appears to be very carefully done — that I have seen that shows plastic being hydrolyzed [broken down] by bacteria,” Woods Hole Oceanographic Institution researcher Tracy Mincer said.

The molecules that form PET are bonded very strongly, said Uwe Bornscheuer, a professor at the University of Greifswald, in an accompanying comment piece in Science.

“Until recently, no organisms were known to be able to decompose it,” he said.

In a Gaian twist, initial genetic examination revealed the bacteria, named Ideonella sakaiensis 201-F6, might have evolved enzymes specifically capable of breaking down PET in response to the accumulation of the plastic in the environment in the past 70 years.

Such rapid evolution was possible, said Enzo Palombo, a professor of microbiology at Swinburne University, given that microbes have an extraordinary ability to adapt to their surroundings.

“If you put a bacteria in a situation where they have only got one food source to consume, over time they will adapt to do that,” he said.

“I think we are seeing how nature can surprise us and in the end the resiliency of nature itself,” Mincer added.

The bacteria took longer to eat away highly crystalized PET, which is used in plastic bottles. That means the enzymes and processes would need refinement before they could be useful for industrial recycling or cleaning up pollution.

“It is difficult to break down highly crystalized PET,” said Kenji Miyamoto from Keio University, one of the authors of the study. “Our research results are just the initiation for the application. We have to work on so many issues needed for various applications. It takes a long time.”

A third of all plastics end up in the environment and 8 million tonnes end up in the ocean every year, creating vast accumulations of life-choking rubbish.

PET is said to make up almost one-sixth of the world’s annual plastic production of 311 million tonnes. Despite PET being one of the more commonly recycled plastics, the World Economic Forum (WEF) reports that only about half is ever collected for recycling and far less actually ends up being reused.

Bornscheuer said that advances in biodegradable plastics and recycling offer hope for the future, “but [this] does not help to get rid of the plastics already in the environment.”

However, the potential applications of the discovery remain unclear. The most obvious use would be as a biological agent in nature, Palombo said.

Bacteria could be sprayed on the huge floating trash heaps building up in the oceans. This method is most notably employed to combat oil spills.

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