Strange fungus has the ability to 'recycle' plastic and rubber waste

Newly discovered fungus in southwestern China is a very "palatable" fungus with the main "food" of plastic and rubber, scientists hope to be able to use them to recycle good plastic. than.

Biodiversity area with hundreds of thousands of species of fungi

Southwest China's Yunnan province is known to be inhabited by many strange fungi. A South African mycologist, Peter Mortimer, who has studied Yunnan mushrooms for more than 10 years at the Kunming Institute of Botany, says some fungi can help solve the problem of plastic and rubber waste in fruit. soil.

"Yunnan has a wide variety of landscapes and climates in a small space, from lowland tropical forests in the south to high mountains in the north. Yunnan is also full of mountains, and mountains are a diverse landscape with various types. forests and soils, creating a great diversity of mushroom habitats".

Although 6,000 species of mushrooms have been discovered in Yunnan, "perhaps that is still a very small part of the total number of mushroom species in this province". Scientists estimate that Yunnan has nearly 100,000 species that are still unknown. Worldwide, scientists have identified about 140,000 species of fungi.

Peter Mortimer holds a new species of mushroom during a mushroom-collecting expedition in the Mekong River region, Yunnan province.

Last year Mortimer, together with Samantha Karunarathna at Qujing Normal University, Yunnan, discovered several new species with a special ability: "they can 'digest' both resin and latex, or high Natural rubber is made from the sap of a tree. These newly discovered fungi could be the key to new green technologies for recycling plastic and rubber waste. Mortimer also had a hunch that the southern tropics of the province might have rubber-eating mushrooms.

'We went to the rubber plantation in Xishuangbanna to look for mushrooms. Mortimer said there was an old discarded plastic bag in the bushes and fungi growing on it and digesting it." Of the species found on the plastic bags, four were new and never-before-seen. find a lot of new species. But the fungus on the plastic bag was discovered to have four new unrelated species, all of which can break down plastic - which is a good find." Especially then, they were also happy because another surprise, these 4 new species of fungi can all digest tree latex in the laboratory.

A rubber tree with white latex residue and autumn gourd in Xishuangbanna, Yunnan province.

The newly discovered Yunnan fungus promises to decompose both latex and plastic very well.
Mortimer said: "Mushrooms that have the ability to destroy plastic have been known for many years, but this is the first time we have discovered them. discovered fungi that can decompose latex. And this is certainly the first mushroom species with dual effects, which can decompose both latex and plastic."

Latex, also known as natural rubber, is a widely used material, outperforming synthetic rubber in many applications, including tires. With the ability to eat plastic or rubber, the fungus can transform the mutant into another biomass. "It looks like white cotton wool, it smells like a wet forest. It can then be used to make fertilizer. , animal feed, building materials, biofoams and packaging".

Mortimer and his team fed their mushrooms with a variety of resins. 'Polyurethane - PU - is the most biodegradable, and that's what we focus on'. The world is suffocating in the midst of plastic waste, nearly 300 million tons are produced each year. Polyurethane-based plastics, which are used to make foam, fibers and tires, account for 8 million tons. Polyurethane is difficult to recycle, but 90% of it ends up in landfills. Even when reprocessed, polyurethane releases polluting chemicals that are harmful to health.

Fungi that can destroy polyurethane in the laboratory were known almost 20 years ago. The practical applications of plastic-eating fungi for polyurethane waste have been discussed by researchers for more than a decade. Recycling experts say the technique of using wild mushrooms, if successful, could replace expensive and unsanitary recycling processes like composting.

Partially digested polyurethane membrane on the left and fully digested on the right in the lab by plastic-eating fungi discovered by Mortimer's team

Nicole Pei, a waste management engineer (founder of Cair Technologies, a Hong Kong company that specializes in providing biological systems to control emissions from wastewater treatment) said: 'Biorecycling proven to be the most economical method for waste and wastewater management. Currently plastics are either landfilled or undergo heat treatment, and heat-based treatment of chlorinated plastics has the potential to generate dioxins and it is very expensive to use fuel to generate enough heat. least".

However, the fungi discovered so far are not believed to be fast enough to digest the plastic, could the newly found Yunnan mushroom make a difference? Mortimer stresses that his research is just getting started, but says the results are promising - the fungi found on plastic bags in Xishuangbanna are voracious PU eaters.

"I'm very excited - these four new species are making strong inroads into PU, showing very high rates of degradation." However, the ability to eat the latex of other similar fungi still requires further research, says Mortimer. assessment. "We're at a very early stage of the process. In the laboratory, these fungi derive their nutrition from the latex, but we have not examined the rate of loss and mass degradation of the latex."

Processed latex slabs are stored in a rubber plantation in Xishuangbanna, Yunnan province

The special "weapon" of the fungus

What allows fungi to "eat" indigestible materials like plastic? Mortimer explains that fungi possess specialized enzymes that no other organism has. These enzymes can break strong bonds in chemical compounds, such as lignin and cellulose, which are indigestible for most living organisms. This feature also allows some species of fungi to digest wood.

However, Mortimer explains that mushrooms do not have just such an enzyme, but 'an arsenal of them; an enzyme cocktail that allows fungi to adapt and benefit from different environments". One thing Mortimer and the researchers are still wondering and are looking for is whether the ability to break down plastic and latex only Is it an "accident" of nature or the result of evolution, he explains, that an enzyme developed to break down wood can also cut molecules like polyurethane. Plastic and latex may be the result of the evolution of fungi to exploit the resources of our polluted world.

Mortimer is now doing more research on the fungi's sap and latex-cutting enzymes and the genes that encode them. If they are different, it is possible that "this ability was developed independently by different fungi, showing you that the fungus is adapting to the environment".

Mortimer added: "We also found a range of other fungi that live directly on the rubber latex on the plantation. Research is ongoing, but the exact characterization and sequence are not yet known. of them".

Cultivation of plastic-eating fungi in the laboratory of Peter Mortimer, Kunming, Yunnan province.

Many other plastic "recycling" mushrooms may be present in Yunnan

To be recycled on an industrial scale, the ingestion of the resin and latex of the fungus Mortimer observed in a petri dish had to be sent to a bioreactor. 'It sounds like a huge and impressive thing, but a bioreactor is nothing more than a steel tank where you maintain the perfect conditions to keep the fungi alive at their best. "Bioreactors are simple, but they can be expensive to operate and build," Mortimer said. He is currently applying for funding.

"Our next step is to set up and operate the bioreactors. We will try to calculate different degradation at different volumes of plastic and fungi, and try growing conditions at the same time. different things to see what makes the fungus most viable. In a year or two, we'll have our own bioreactor to test this."

Mortimer then plans to apply for patents for methods to decompose plastic by fungi in bioreactors. He now holds a patent for the first plastic-eating fungus of the genus Aspergillus that his team found in Yunnan.

'In 2022 we have patented, at the petri dish level, processes to prepare the plastic, exposing it to some form of treatment - such as ultraviolet light to help break it down. first and then let the fungus grow right on it."

Mortimer explains: 'New species are proving to be more efficient, and at the bioreactor level, there will be different patents due to different growing conditions. Each mushroom species, or cocktail of species, may be a separate patent. Also as we get into different plastics, a series of patents will follow."

Peter Mortimer examines fungi in his laboratory, Kunming, Yunnan province.

The fungi that Mortimer's team found showed early promise, and the search for more fungi is ongoing. He also said that in order for industrial mushroom-based plastic recycling to be commercially viable, the fungi used must be 'chilled out' and have the 'appropriate chemical arsenal'. The term "chilled out" refers to habitat acceptance, which means they won't be picky about their conditions in the bioreactor. "They have to be comfortable in a general environment where you don't have a large energy cost to keep the temperature high or low, maintaining specific oxygen and carbon dioxide levels." And 'chemical arsenal' refers to enzymes that exist in fungi.

Mortimer also hopes to find fungi that can also break down harder plastics. "Mushrooms need weapons, enzymes to degrade, not just PU, because with PU we're competing with a huge recycling industry. But what if we start breaking down resistant plastics? stronger force like polyvinyl, then we can really stand out." 

For this reason, Mortimer says scientists will need more than one species of "chilled out" fungus. "For a final solution, in a bioreactor, we need such a fungus, with different enzymes to digest different plastics." He also added that "Looking further into the future, I could also see an aerosol made of fungal enzymes that could be sprayed onto plastic".

In addition, Mortimer explains, fungi could also provide a way to recycle melted plastic that cannot be recycled using existing methods. "Conventional recycling doesn't work for things like the spandex that's built into your jeans and the Tetra Pack that has an aluminum lining inside. Potentially, a fungus could grow into such waste. and selectively digest the different components of those integrated systems".

Can mushrooms live up to this potential and provide a green plastic waste recycling solution? This is possible if we find the right mushroom. "The problem is the time it takes for fungi with the right chemical arsenal to appear on their own. Statistically speaking, they are most likely in Yunnan."

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