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Plastic-eating bacteria could fuel recycling revolution

EcoNote | April 8, 2016 | By:

Researchers at Japan’s Kyoto University have discovered a plastic-eating bacteria that could have a major impact on recycling efforts around the world.

Similar research by San Francisco-based Ambercycle Inc. has been rewarded with a 250,000-euro ($283,000) Global Change Award funded by the H&M Conscious Foundation, an arm of Stockholm, Sweden-based clothing retailer H&M.

According to a story at, the Kyoto team has found a plastic-eating microbe after five years of searching through 250 samples of rubbish. They isolated a bacteria that could live on polyethylene terephthalate (PET), a common plastic used in bottles and clothing. They named the new species of bacteria Ideonella sakaiensis.

Unlike natural polymers, such as plant cellulose, plastics aren’t generally biodegradable. The Conversation story notes bacteria and fungi co-evolved with natural materials, developing biochemical methods to harness the resources from dead matter. But plastics have been around for only about 70 years, so microorganisms haven’t evolved to the point at which they can latch onto the plastic fibers, break them up, and then use the resulting chemicals as a source of energy and carbon that they need to grow.

A form of plastic-eating microbes had already been discovered, The Conversation notes. But differences abound. First, previous reports were of tricky-to-cultivate fungi; in this case, the microbe is grown easily. The researchers more or less left the PET in a warm jar with the bacterial culture and some other nutrients, and a few weeks later all the plastic was gone.

Second—and the real innovation—is that the team has identified the enzymes that Ideonella sakaiensis uses to breakdown PET. All living things contain enzymes that they use to speed up necessary chemical reactions. The Kyoto researchers identified the gene in the bacteria’s DNA that is responsible for the PET-digesting enzyme, and were able to manufacture more of the enzyme and then demonstrate that PET could be broken down with the enzyme alone.

This could open a new approach to plastic recycling and decontamination. Currently, most plastic bottles are not truly recycled. Instead they are melted and reformed into other hard plastic products. Packaging companies typically prefer freshly made “virgin” plastics that are created from chemical starting materials that are usually derived from oil.

The PET-digesting enzymes offer a way to truly recycle plastic, the report notes. They could be added to vats of waste, breaking all the bottles or other plastic items down into easy-to-handle chemicals. These could then be used to make fresh plastics, producing a true recycling system.

Manufactured enzymes are already used in a wide range of everyday items. Biological washing powders contain enzymes that digest fatty stains. The enzymes known as rennet that are used to harden cheese once came from calves’ intestines but are now manufactured using genetically engineered bacteria.

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