Scientists Discover Microbes That Could Revolutionize Plastic Recycling

These bacteria and fungi can break down certain plastics at cool temperatures, saving money and energy compared to some current methods

submerged diver with large and small plastic fragments in the water
Turkish world-record-holding free-diver Sahika Ercumen swims amid plastic waste on June 27, 2020, to raise awareness about plastic pollution. Sebnem Coskun / Anadolu Agency via Getty Images

To tackle the world’s mounting plastics problem, humans may have to use every tool in the arsenal—even microscopic bacteria and fungi. High in the Swiss Alps and the Arctic, scientists have discovered microbes that can digest plastics—importantly, without the need to apply excess heat. Their findings, published this month in the journal Frontiers in Microbiology, could one day improve plastic recycling.

From the Great Pacific Garbage Patch to the tiny microplastics that pervade our drinking water, tea, fish and blood, it’s no secret that plastic pollution is a big, global issue. Since its production exploded during and after World War II, humans have created more than 9.1 billion tons of plastic—and researchers estimate that less than one tenth of the resulting waste has been recycled.

To make matters worse, the most common recycling option—when plastic is washed, processed and turned into new products—doesn’t actually reduce waste: The recycled materials are often lower quality and might later end up in a landfill all the same.

In reality, this strategy “is not recycling,” Alain Marty, chief science officer at Carbios, a French company developing recycling alternatives, told Undark’s Ula Chrobak last year. “At the end… you have exactly the same quantity of plastic waste.”

So, researchers are looking for solutions to the plastics problem that go beyond conventional recycling—and one process they’ve experimented with is breaking down plastics using microorganisms. But this isn’t practical quite yet—typically, the known plastic-digesting microbes can only do so at warm temperatures above 85 degrees Fahrenheit. When done at an industrial scale, the amount of energy needed to generate that much heat makes the process emit more carbon—and cost more money.

But the enzymes from the microorganisms found in the Arctic and Swiss Alps can function at cooler temperatures: They were able to break down biodegradable plastics at 59 degrees Fahrenheit, opening doors to a more efficient system.

“These organisms could help to reduce the costs and environmental burden of an enzymatic recycling process for plastic,” co-author Joel Rüthi, currently a guest scientist at the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), says in a statement.

blocks of colored plastics
Colored plastic bottles ready to be recycled in Pontedera, Italy, including some collected by fishermen. Laura Lezza via Getty Images

In the new study, Rüthi and his colleagues sampled 19 strains of bacteria and 15 types of fungi in Greenland, Switzerland and the Svalbard archipelago in Norway. The microbes were growing on pieces of free-lying plastic or ones that had been intentionally buried in the ground for one year.

Of the total 34 types of microbes examined, 19 were successfully able to break down a form of plastic called polyester-polyurethane, and 17 could break down two types of biodegradable plastic mixtures. But none could digest polyethylene, the most commonly produced plastic, which is used in food containers and plastic bags.

The study described a “straightforward” way to isolate these bacteria and fungi, which naturally occur in the wild, Ludmilla Aristilde, a molecular biochemist at Northwestern University who was not involved in the study, tells Smithsonian magazine.

“Exploiting natural microbes can provide a ‘head start,’” when it comes to designing a strategy for bio-recycling, or using living organisms to break down plastic waste, Aristilde says.

With further study, the authors hope to determine the optimal temperature for these enzymes to function. They also hope to identify the microbes’ specific mechanisms for breaking down the plastics.

“The next big challenge will be to identify the plastic-degrading enzymes produced by the microbial strains and to optimize the process to obtain large amounts of proteins,” co-author Beat Frey, a senior scientist and group leader at WSL, says in the statement.

Last year, scientists reported other creative ways to break down plastics with enzymes, such as those in the saliva of wax worms and in the guts of beetle larvae.

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