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Found microbes that can digest plastic at low temperatures | microbiology



Microbes capable of digesting plastic at low temperatures have been discovered by scientists in the Alps and the Arctic, which could be a valuable tool in recycling.

Many micro-organisms that can do this have already been discovered, but usually they can only work at temperatures above 30°C (86°F). This means that their use in industrial practice is prohibitively expensive due to the required heating. This also means that their use is not carbon neutral.

Scientists at the Swiss Federal Institute WSL have found microbes capable of doing this at 15°C, which could lead to a breakthrough in microbial recycling. Their findings were published in the journal frontiers of microbiology.

Dr. Joel Ruti of WSL and colleagues took samples of 19 strains of bacteria and 15 fungi growing on loose or intentionally buried plastic stored in the ground for one year in Greenland, Svalbard and Switzerland. They allowed the microbes to grow as single culture strains in a lab in the dark at 15°C and tested them to see if they could digest different types of plastic.

The results showed that the bacterial strains belonged to 13 genera in the actinobacteria and proteobacteria phyla, while the fungi belonged to 10 genera in the ascomycota and mucoromycota phyla.

The plastics tested included biodegradable polyethylene (PE) and biodegradable polyester polyurethane (PUR), as well as two commercially available biodegradable blends of polybutylene adipate terephthalate (PBAT) and polylactic acid (PLA).

None of the strains could digest PE even after 126 days of incubation on these plastics. But 19 strains (56%), including 11 fungi and 8 bacteria, were able to digest polyurethane at 15°C, while 14 fungi and 3 bacteria were able to digest PBAT and PLA plastic blends.

Ryti said: “Here we show that new microbial taxa derived from the ‘plastisphere’ of alpine and arctic soils are able to break down biodegradable plastic at 15°C. These organisms can help reduce the cost and environmental burden of enzymatic plastic recycling.”

He said it was surprising that most of the strains tested were able to degrade even one of the tested plastics.

The scientists also tested the best of them and found that they were two uncharacterized species of fungi from the genera neodevriesia and lachnellula that can digest all the plastics tested except polyethylene.

Although plastics have only been widely used since the 1950s, microbes can degrade polymers because they resemble some of the structures found in plant cells.

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“I have a family, the idea of two years in prison really does frighten me: the new laws have made me more apprehensive about protests.”

Both Kvelde and Jacobs have previously been arrested for protesting in NSW, over a March 2022 protest at Port Botany. That protest was the catalyst for the state government introducing the new anti-protest laws they are challenging.

However, the state of NSW is arguing the two climate protesters do not have standing to challenge the new laws because they have not faced charges under the new legislation, section 214A of the Crimes Act.

Michael Sexton SC, the solicitor general for NSW, told the court the legislation carried a “legitimate purpose” in wanting to deter conduct that deleteriously impacted upon major roads and public facilities, and the right of others to use them.

Sexton argued the burden on the implied freedom of political communication in this case was “almost zero”.

But Free, for the protesters, told the court the new laws were introduced for the express purpose of “deterring people from participating in protest actions”.

In his second reading speech before parliament, read into court on Thursday, the then attorney general Mark Speakman, said the bill, “in no way seeks to impose a general prohibition on protests”.

“The government supports the rights of all individuals to participate in lawful protest. Freedom of assembly and speech have long been recognised by Australian courts as important rights that are integral to a democratic system of government; however, the right to protest must be weighed against the right of other members of the public to move freely and not be obstructed in public places.

“There are plenty of other ways for individuals to express their strongly held views, and the Government will not stand by as the few seek to disrupt and dispossess the rights of many.”

Justice Michael Walton has reserved his decision.

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