In 2013 alone, around 56 million tons of polyethylene terephthalate were produced in the world, also known as PET. Their accumulation in ecosystems around the world is a growing problem. To date, very few species of microorganisms have been found that decompose this polymer.
Scientists from several Japanese centers have published a study in Science in which they have collected 250 samples of PET waste and studied them for bacterial candidates that depend on PET sheets as the main source of carbon for their growth.
“Until now there was no report on how to degrade PET to carbon dioxide and water. One of the reasons is because PET has crystalline structures and also a hydrophobic chemical nature ”, points to Sinc Kohei Oda, lead author of the study and researcher at the Kyoto Institute of Technology (Japan).
In this new work, the experts have identified a new enzyme in the bacteria, which they have called Ideonella sakaiensis201-F6, which can almost completely degrade a thin PET sheet after six weeks at a temperature of 30 ºC.
Furthermore, further investigation ended up identifying another enzyme, ISF6_4831, which works with water to break down PET into an intermediate substance that can in turn be broken down into a second enzyme, ISF6_0224.
“We were able to isolate these microorganisms at a PET bottle recycling site. Our study is just the beginning to develop a technology that can degrade PET material that is wasted on an industrial scale. And we will do it using the group of bacteria or Ideonella sakaiensis or enzymes of the strain as soon as possible ”, adds the scientist.
These two enzymes alone are capable of breaking down PET into simpler structural units. What is surprising, according to the researchers, is that they are also extremely unique in their function, when compared to the closest known enzymes from other bacteria.
This makes scientists question the evolution of these plastic-eating bacteria. “We don't have any evidence so far. We assume that its enzyme evolved from cutinase, because under special conditions it has a certain capacity to degrade PET ”, he concludes.
Shosuke Yoshida et al. "A bacterium that degrades and assimilates poly (ethylene terephthalate)" Science 351 (6278): 1196-1199, March 11, 2016.
Photo: Fish and plastic bags share space in the coral reef that surrounds the ‘Naama Bay’ tourist complex, in the Red Sea, Egypt / EFE