How ‘super-enzymes’ that eat plastics could curb our waste problem, no The Guardian.
[...]In 2016 researchers led by microbiologist Kohei Oda of the Kyoto Institute of Technology in Japan reported a surprise discovery. Oda’s team visited a recycling site that focused on items made of polyethylene terephthalate (PET), a clear plastic that is used to make clothing fibres and drinks bottles.
Like all plastics, PET is a material made up of long string-like molecules. These are assembled from smaller molecules strung together into chains. The chemical bonds in PET chains are strong, so it is long-lasting – exactly what you do not want in a single-use plastic.
Oda’s team took samples of sediment and wastewater that were contaminated with PET, and screened them for micro-organisms that could grow on the plastic. It found a new strain of bacterium, called Ideonella sakaiensis 201-F6. This microbe could grow on pieces of PET. Not only that: Oda’s team reported that the bacterium could use PET as its main source of nutrients, degrading the PET in the process.
The finding made headlines around the world, but it was not the first example of an organism that could degrade plastics. Reports of plastic-munching microbes date back to at least the early 1990s. The earliest examples were arguably less remarkable, because they could only eat plastics that were chemically flimsy or biodegradable. But by the 2000s researchers had found enzymes that could tackle tougher plastics.
[...]So why did Ideonella sakaiensis 201-F6 cause such a stir? “The difference with the 2016 paper was this micro-organism could use the plastic as its sole energy and food source,” says John McGeehan of the University of Portsmouth. “That’s actually quite surprising and it kind of shows evolutionary pressure in action. If you’re the first bacterium in that rubbish pile that suddenly has a taste for plastic, then you’ve got an unlimited food source.”
[...] This is now bearing fruit. In 2020 McGeehan’s team reported that it had linked the PETase and MHETase enzymes together. This “super-enzyme” could eat PET about six times faster than the two enzymes working separately. Other groups such as Blank’s MIX-UP have produced modified enzymes of their own.
Meanwhile there is evidence that microbes all around the world are evolving similar abilities. A study published in October 2021 looked at microbial DNA from a range of habitats. In areas with high levels of plastic pollution, the researchers found that the microbes were more likely to have enzymes with plastic-degrading tendencies. In line with this, a 2020 study identified a soil bacterium that can feed on some of the components of polyurethane, which releases toxic chemicals when it breaks down.
The question now becomes: how significant a role can these enzymes really play in reducing plastic pollution?
[...] So far, most of the activity has been in universities, but some groups are attempting to commercialise the technology.
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Como muitos desde 2016 interesso-me por este tema. O Universo é espantoso e infinitos os milagres da Natureza e da Ciência. Na mesma linha de preocupações, outro assunto com interesse é o da dessalinização. Estudar e trabalhar nestas áreas deve ser das tarefas mais estimulantes e gratificantes do mundo moderno.
