Every year, we churn out 56 million tons of plastics to protect our food, water and consumer products from contamination, but less than 14 percent of these cans, bottles and wrappers are recycled. Now, researchers in Japan have discovered a new kind of bacteria that can break down one common form of plastic into its chemical building blocks, a discovery that could save landfill space, oil and energy consumed in plastics manufacturing.
"We have shared the possibility of biological recycling of plastic," said Shosuke Yoshida, an author on the new paper coming out today in the journal Science. "We want to develop this discovery into the application. This is the very first step."
Polyethylene terephthalate (PET) is a widely used, clear plastic made from two simple compounds, however until now, nobody has found an organism that can break it down.
Right now, when you recycle a PET bottle, it usually has bits of food or other contaminants that are difficult to remove. The PET is taken to a recycling facility, shredded and then turned into a lower-grade material, such as carpets, for example.
But using a plastic-munching bacteria instead could save energy and the environment, according to Yoshida, a professor of applied biology at Kyoto Institute of Technology.
For five years, a team of Japanese researchers collected 250 PET debris–contaminated environmental samples including sediment, soil, wastewater, and activated sludge from a PET bottle recycling facility.
Using these samples, researchers screened for microorganisms that used PET film as their food source. The team initially found a whole ecosystem of bacteria living on the PET, but only one species that could actually break down the surface of the plastic using two unique enzymes. The end product are two environmentally benign chemicals that make up PET -- ethylene glycol and terephthalic acid.
The bug-driven biologically recycling is slow, it takes six weeks, but Yoshida believes the process can be sped up with a bit of industrial engineering. Bacteria are often harnessed to ferment alcoholic products, for example, while yeast is harnessed to bake bread.
Uwe T. Bornscheuer, professor at the Institute of Biochemistry in Griefswald University in Germany, says this breakdown has never been done before. Other teams have found worms that can munch Styrofoam, but it's not clear how fast they work and whether they have other food sources at the same time.
This new bacteria, Ideonella sakaiensis, does the entire job, Bornscheuer explained.
"This one can do it from the beginning to end," he said via Skype.
PET was invented in the late 1940s and became a widespread consumer item in the decades that followed. Somehow, this bacteria quickly evolved to use it as a food source in a relatively short time.
"This gives us hope that there are other microbes that can eat up other plastics as well," he said.