Plastics, Japanese researchers discover a PET-eating bacterium

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Ideonella sakaiensis can biodegrade bottle and packaging plastics by breaking them down to small pieces

In spite of the huge variety of food habits of the world’s fauna, it was always considered impossible to find organisms that feed on plastics. Plastic waste is everywhere, whole islands of it are floating in the oceans, but until now, it seemed like no organism was able to digest it. However, in front of a recycling facility in Japan, a group of Japanese researchers discovered a bacterium that was feasting on a kind of plastics widely used in clothing, plastic bottles and food packaging.

The bacterium was called Ideonella sakaiensis, after the Japanese city of Sakai, where it was caught in the act of eating up PET waste. According to Shosuke Yoshida, microbiologist at the Kyoto University and author of a study recently published by the Science magazine, this is a unique discovery: this bacterium seems able to decompose PET.

Most plastics are impossible to break down for microbes, because they are made of large chains of repeating molecules: the polymers. The entire chain is far larger than the individual microbe. “So the organism can’t take it inside the cell to metabolize it – says John Coates, a microbiologist at the University of California, Berkeley – Imagine a baby trying to eat an enormous pizza from the middle. It can’t do it. The pie is too big”.

Ideonella sakaiensis has two enzymes that can cut the polymer in dices. In other words, the baby of the example gets a pizza cutter. The bacterium can then eat the pieces, metabolize them and convert them into carbon dioxide and water.

After isolating the bacterium, the Japanese researchers were able to watch it disintegrate a plastic film in about six weeks. The system seems to work, but it’s quite slow: it will hardly eat up a whole landfill of plastic waste.

But with more research, it is expected that the bacterium can be engineered for more ambitious goals. In the past, certain species of fungi have been found to be able to degrade plastics, but bacteria are easier to engineer for other purposes.

Anyway, according to researchers, recycling will likely remain a better option. Biodegrading materials release carbon dioxide into the atmosphere, which would contribute to global warming. But in cases where recycling is not feasible, this bacterium could prove a useful alternative.

Read the Japanese study published on the Science magazine

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