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Headlines in the media screaming: Humans dump 8 million tonnes of plastics into the oceans each year. That's five grocery bags of plastic for every foot of coastline in the world.

Plastic, plastic, plastic and harmful plastic everywhere on this planet. How can we get rid of it?

The question that has been eating our brains since plastic came into existence in our lives, has found an answer in plastic consuming worms.

Meet the plastic-eating mealworms ...

 
Mealworms munch on Styrofoam, a hopeful sign that solutions to plastics pollution exist. (Photo: Yu Yang)

A combination of American and Chinese researchers, show that the mealworm ( larvae of Tenebrio molitor Linnaeus) can live on a plastic diet. The larvae form of the darkling beetle can eat styrofoam and other forms of polystyrene show two companion studies co-authored by Standford's Wei-Min Wu. The research shows  the evidence that bacteria  inside an animal's gut (a PS-degrading bacterial strain was isolated from the guts of the mealworms, Exiguobacterium sp. strain YT2 ) digested the plastic .

In the  study 100 mealworms were used and they ate between 34 and 39 milligrams of Styrofoam. This is about the weight of a small pill per day. The worms converted about half of the styrofoam into carbon dioxide, as they would with any food source.

Within 24 hours, they excreted the bulk of the remaining plastic as biodegraded fragments that look similar to tiny rabbit droppings. Mealworms fed on a steady diet of styrofoam were as healthy as those eating a normal diet, Wu said, and their waste appeared to be safe to use as soil for crops.

These findings may solve the global plastic pollution problems.
 
Source:

A CSIC scientist discovers that wax worms eat plastic

The insect is able to quickly biodegrade polyethylene, the plastic used for shopping bags and food packaging

A research scientist at the Spanish National Research Council (CSIC), Federica Bertocchini, has discovered that wax worms (Galleria mellonella), which usually feed on honey and wax from the honeycombs of bees, are capable of degrading plastic. This worm is capable of biodegrading polyethylene, one of the toughest plastic materials that exists, and which is used to make shopping bags and food packaging, amongst other things. The discovery has been patented by the research scientists. The CSIC scientist worked on this research with Paolo Bombelli and Chris Howe from the University of Cambridge. The paper has been published in the journal Current Biology.

Every year, around 80 million tonnes of polyethylene, a material which is extremely tough and difficult to degrade, are produced around the world. For example, low-density polyethylene plastic bags, take around 100 years to decompose completely, with the toughest, most resistant ones taking up to 400 years to break down. Every year, the average person uses more than 230 plastic bags, generating more than 100,000 tons of this type of plastic waste.

Currently, the very long processes of chemical degradation, which require the use of corrosive liquids such as nitric acid can take up to several months. This is the first time that a scientific research team has found a natural solution which has proven itself capable of degrading this material. "Plastic is a global problem. Nowadays waste can be found everywhere, including in rivers and oceans. Polyethylene in particular is very resistant, and as such is very difficult to degrade naturally".

These scientists have carried out many experiments to test the efficacy of these worms in biodegrading polyethylene. 100 wax worms are capable of biodegrading 92 milligrams of polyethylene in 12 hours, which really is very fast , they found after the tests. Following the larva phase, the worm wraps itself in a whitish-coloured cocoon or chrysalis. The researchers also discovered that by simply having the cocoon in contact with polyethylene, the plastic biodegrades.

The composition of beeswax is similar to that of polyethylene. According to the researchers, this may be the reason why the worm has developed a mechanism to dispose of this type of plastic. "We still don't know the details of how this biodegradation occurs, but there is a possibility that an enzyme is responsible. The next step is to detect, isolate, and produce this enzyme in vitro on an industrial scale. In this way, we can begin to successfully eliminate this highly resistant material", explain the researchers. 

A chance discovery

The scientist, who is also an amateur beekeeper, discovered this attribute of wax worms quite by chance. One day she discovered that the honeycomb panels stored in her house were covered with worms which were feeding on the leftover honey and wax from her bees.

"I removed the worms, and put them in a plastic bag while I cleaned the panels. After finishing, I went back to the room where I had left the worms and I found that they were everywhere. They had escaped from the bag even though it had been closed and when I checked, I saw that the bag was full of holes. There was only one explanation: the worms had made the holes and had escaped. This project began there and then", says the CSIC scientist.

The wax worm

The wax worm, also known as the honey worm, is a lepidopteran insect which can reach three centimeters in length in its larval phase and can be found anywhere in the world. They feed on honey and wax in beehives, where they also find a suitable temperature for their development.

Wax worm larvae have a life expectancy of between six and seven weeks at an optimal temperature for growth of 28 to 34 degrees Celsius. The larvae produce silk and make a cocoon in which they will go through their last metamorphosis: their conversion into moths.

Source: EurekAlert

Also, Superworms digest plastic, with help from their bacterial sidekicks. superworms (Zophobas atratus) are beetle larvae that are often sold in pet stores as feed for reptiles, fish and birds. In addition to their relatively large size (about 2 inches long), these worms have another superpower: They can degrade polystyrene plastic. Now, researchers reporting in ACS' Environmental Science & Technology have linked this ability to a strain of bacteria that lives in the larvae's gut.

Hong Rae Kim et al. Biodegradation of Polystyrene by Pseudomonas sp. Isolated from the Gut of Superworms (Larvae of Zophobas atratus), Environmental Science & Technology (2020). DOI: 10.1021/acs.est.0c01495

Other promising research works on this:
 

Dr Ambica Devi, a Vizag (Andhra Pradesh State, India)-based research scholar, has isolated a bacterial strain from sea water which degrades polythene bags by 40 per cent in just two months. Usually it takes several decades for polythene bags to completely degrade, and they leach harmful chemicals into the soil.

Dr Devi earlier worked as a scientist in Andhra University before she was selected by the Vizag Steel Plant as a junior manager in the microbiology department. The isolated bacterial strain was identified by the Institute of Microbial Technology based in Chandigarh as a unique strain used for bio-degradation of polythene, namely Achromobacter denitrificans strain S1. They have allotted an accession number for further studies.

When the bacterial strain was applied on the effluents from the Vizag steel plant, it drastically reduced the toxin levels such as cyanides and phenols. Mutation of this strain has resulted in higher degradation of plastic than the wild strain. Further studies on this bacterium can help speed up the plastic degradation and show better ways to tackle the problem.

Dr Devi was awarded a PhD for this project by the Andhra University.


Bacteria Devour Polluting Plastic in Landfills

Researchers have discovered world's first polyethylene-eating bacterium

A tiny microbe one day could devour the millions of metric tons of polyethylene terephthalate, or PET, that pile up in landfills each year. Researchers in Japan have discovered the world’s first PET-eating bacterium, a critter that uses PET as its major carbon and energy source.

To find microbes that could pull PET apart, a team led by Kohei Oda of Kyoto Institute of Technology and Kenji Miyamoto of Keio University screened 250 sediment, soil, wastewater, and activated sludge samples from a PET bottle recycling facility in Sakai, Japan. After some careful microbial sleuthing, they found one bacterium that thrived on PET films and named it Ideonella sakaiensis after the city where it was found (Science 2016, DOI: 10.1126/science.aad6359).

Some bacteria think plastic is fantastic

Bacteria isolated from outside a bottle-recycling facility can break down and metabolize plastic. The proliferation of plastics in consumer products, from bottles to clothing, has resulted in the release of countless tons of plastics into the environment. Yoshida et al. show how the biodegradation of plastics by specialized bacteria could be a viable bioremediation strategy (see the Perspective by Bornscheuer). The new species, Ideonella sakaiensis, breaks down the plastic by using two enzymes to hydrolyze PET and a primary reaction intermediate, eventually yielding basic building blocks for growth.

A bacterium that degrades and assimilates poly(ethylene terephthalate) : http://science.sciencemag.org/content/351/6278/1196

PET can be hydrolyzed to its monomers chemically, but this process can be slow and usually requires high temperatures and pressures. Fungi that can break down PET have been identified previously, but the bacterium identified by Oda and Miyamoto’s group appears to be more efficient than these. In fact, I. sakaiensis dices up polymer at a surprisingly mild 30 °C. 

Scientists identified another microbe that could help degrade polyurethane-based plastics

A strain of bacteria capable of degrading some of the chemical building blocks of polyurethane.

"The bacteria can use these compounds as a sole source of carbon, nitrogen and energy'. This finding represents an important step in being able to reuse hard-to-recycle PU products. 

The team out of Germany managed to isolate a bacterium, Pseudomonas sp. TDA1, from a site rich in brittle plastic waste that shows promise in attacking some of the chemical bonds that make up polyurethane plastics.

The researchers performed a genomic analysis to identify the degradation pathways at work. They made preliminary discoveries about the factors that help the microbe metabolize certain chemical compounds in plastic for energy. They also conducted other analyses and experiments to understand the bacterium's capabilities (A, B). This particular strain is part of a group of bacteria that are well-known for their tolerance of toxic organic compounds and other forms of stress. That trait is also named solvent-tolerance and is one form of extremophilic microorganisms.

In addition to polyurethane, the P4SB consortium, which includes the Helmholtz Centre for Environmental Research-UFZ, is also testing the efficacy of microbes to degrade plastics made of polyethylene terephthalate (PET), which is widely used in plastic water bottles.

A. Frontiers in MicrobiologyDOI: 10.3389/fmicb.2020.00404 , https://www.frontiersin.org/articles/10.3389/fmicb.2020.00404/full

B. https://phys.org/news/2020-03-scientists-microbe-degrade-polyuretha...

Plastic Eating Fungi

Scientists from the Kunming Institute of Botany (KIB), Chinese Academy of Sciences have recently identified a fungus which could help deal with the problem of plastic waste by using enzymes to rapidly break down plastic materials. Their findings have been published in Environmental Pollution. 
 
Plastic polymers take many years to decompose, as due to their xenobiotic nature—meaning that they did not exist before their synthesis by humans—they are not easily broken down by the bacteria, fungi and small creatures that feed on other waste matter. Even when they do somewhat degrade, tiny particles of plastic may persist in the environment, with unknown consequences for human and environmental health. However, the KIB team believe they may have found an unexpected solution to our growing plastic problem in the form of a humble soil fungus. “We knew that one way to do this would be to look to solutions which already existed in nature, but finding microorganisms which can do the job isn’t easy,” the authors said. In the end, the research team found their plastic-eating fungus living in an appropriate venue—a rubbish tip in Islamabad, Pakistan. Watched by crows and vultures, the researchers took samples of soil and various pieces of rubbish in hopes of finding an organism which could feed on plastic waste in the same way that other fungi feed on dead plant or animal material. Aspergillus tubingensis is a fungus which ordinarily lives in the soil. In laboratory trials, the researchers found that it also grows on the surface of plastics. It secretes enzymes onto the surface of the plastic, and these break the chemical bonds between the plastic molecules, or polymers. Using advanced microscopy and spectroscopy techniques, the team found that the fungus also uses the physical strength of its mycelia—the network of root-like filaments grown by fungi—to help break apart the polymers. Plastics which persist in the environment for years can be broken down by A. tubingensis in a matter of weeks, the scientists say. The fungus’ performance is affected by a number of environmental factors including pH, temperature and the type of culture medium used. 
 
This could pave the way for large-scale use of the fungus in waste treatment plants or soils already contaminated by plastic waste. The discovery of A. tubingensis’ appetite for plastic joins the growing field of ‘mycoremediation,’ which investigates the use of fungi in removing or degrading waste products including plastic, oil and heavy metals. Mycologists estimate that only a small proportion of all fungi species have yet been described, which means that vast numbers of potentially useful species are still to be found. However, the destruction of habitats such as natural forests means that many fungi species are likely being lost before they can be identified, let alone tested for possible uses. If this continues, we may come to rely more and more on those species we can find in man-made environments—and more scientists may find themselves doing fieldwork in rubbish tips rather than rainforests. 
 

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Scientists Discover Backyard Fungi That Can Break Down Tough Plastic in Just 140 Days

Almost a third of the world's plastic waste is polypropylene, a hardy plastic used to make bottle caps and food containers that can take hundreds of years to degrade. But now, scientists have harnessed two strains of fungi found in soils to break down lab samples of polypropylene in just 140 days.

The two fungi, Aspergillus terreus and Engyodontium album, made a meal of the plastic in the lab experiments: Between 25 and 27 percent of samples were devoured after 90 days, and the plastic was completely broken down after 140 days, the researchers report.

While it might be a speed record for fungi, plastic-munching bacteria recently discovered in a compost heap have been able to break down 90 percent of PET, or polyethylene terephthalate, in just 16 hours. But a bit of healthy competition is good; that's how evolution works.

Recent studies suggest some fungi may even degrade some of the 'forever chemicals' like PFAS, but the process is slow and not yet well understood.

https://www.nature.com/articles/s41529-023-00342-9

https://www.sciencealert.com/scientists-discover-backyard-fungi-tha...

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Meet The caterpillar larvae 'plastivores' that consume and metabolize polyethylene
https://phys.org/news/2020-03-caterpillar-larvae-plastivores-consum...

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Structural biology—plastic degradation by using wax worm saliva

Plastic waste management is a pressing ecological, social, and economic challenge that has looked to diverse chemical-biology strategies to facilitate biodegradation. In a new report now on Science Advances,  a research team in structural and chemical biology, molecular biology, and microbial biology,  used the saliva of the lepidopteran Galleria mellonella larvae, to oxidize and depolymerize polyethylene within hours at room temperature.

Using cryo-electron microscopy (cryo-EM) the team analyzed the saliva of the microorganisms directly from the native source. Based on 3D reconstructions, they revealed the composition of the buccal secretions to belong to four hexamerins that can oxidize and degrade polyethylene.

Using cryo-EM data and X-ray analysis, they showed the proteins self-assemble into three macromolecular complexes with distinct structural differences to regulate their activity. The results indicated the possibilities of exploring the functionalities of hexamerins for biotechnological functions in vivo.

 Mercedes Spínola-Amilibia et al, Plastic degradation by insect hexamerins: Near-atomic resolution structures of the polyethylene-degrading proteins from the wax worm saliva, Science Advances (2023). DOI: 10.1126/sciadv.adi6813

Jeannette M. Garcia et al, The future of plastics recycling, Science (2017). DOI: 10.1126/science.aaq0324

Views: 1450

Replies to This Discussion

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Researchers in China and the US have developed a method to convert plastic waste into useful liquid fuels or chemical feedstocks. The research was published in Science Advances. 

Efficient and selective degradation of polyethylenes into liquid fuels and waxes under mild conditions

http://advances.sciencemag.org/content/2/6/e1501591

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https://phys.org/news/2020-07-species-darkling-beetle-larvae-degrad...

A new species of darkling beetle larvae that degrade plastic

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https://www.newsgram.com/bacteria-eats-plastic/

This Bacteria Eats Plastic! German scientists say they have identified a strain of bacteria that is feeding on polyurethanes, a plastic resistant to biodegradation. 

German scientists say they have identified a strain of bacteria that is feeding on polyurethanes, a plastic resistant to biodegradation. A team of researchers at the Helmholtz Center for Environmental Research in Leipzig, Germany, has found that a strain of soil bacterium, identified as Pseudomonas putida, can produce enzymes to digest polyurethanes thus making it biodegradable. The German team says the bacterium found in the soil surrounding a heap of plastic waste was feeding on polyurethane diol, which is used in plastic as a component that protects products from corrosion. Follow NewsGram on Twitter to stay updated about the World news. Hermann Heipieper, one of the researchers and author of the study published in the journal Frontiers in Microbiology, said “this finding represents an important step in being able to reuse hard-to-recycle (polyurethane) products.” The study offers hope of ridding the planet of the growing quantities of discarded plastic products that threaten human and animal life. But some scientists are skeptical.

Scientists discover microbes in the Alps and Arctic that can digest plastic at low temperatures

Finding, cultivating, and bioengineering organisms that can digest plastic not only aids in the removal of pollution, but is now also big business. Several microorganisms that can do this have already been found, but when their enzymes that make this possible are applied at an industrial scale, they typically only work at temperatures above 30°C.

The heating required means that industrial applications remain costly to date, and aren't carbon-neutral. But there is a possible solution to this problem: finding specialist cold-adapted microbes whose enzymes work at lower temperatures.

Scientists  knew where to look for such microorganisms: at high altitudes in the Alps, or in the polar regions. When they did that, novel microbial taxa obtained from the 'plastisphere' of alpine and arctic soils were able to break down biodegradable plastics at 15°C. Their findings are published in Frontiers in Microbiology.

How did the ability to digest plastic evolve? Since plastics have only been around since the 1950s, the ability to degrade plastic almost certainly wasn't a trait originally targeted by natural selection.

Microbes have been shown to produce a wide variety of polymer-degrading enzymes involved in the break-down of plant cell walls. In particular, plant-pathogenic fungi are often reported to biodegrade polyesters, because of their ability to produce cutinases which target plastic polymers due their resemblance to the plant polymer cutin.

Discovery of plastic-degrading microbial strains isolated from the alpine and Arctic terrestrial plastisphere, Frontiers in Microbiology (2023). DOI: 10.3389/fmicb.2023.1178474 , www.frontiersin.org/articles/1 … cb.2023.1178474/full

Plastic-eating fungi thriving in man-made 'plastisphere' may help tackle global waste

A new study published in the Journal of Hazardous Materials by researchers  has identified a diverse microbiome of plastic-degrading fungi and bacteria in the coastal salt marshes of Jiangsu, China.

The international team of scientists counted a total of 184 fungal and 55 bacterial strains capable of breaking down polycaprolactone (PCL), a biodegradable polyester commonly used in the production of various polyurethanes. Of these, bacterial strains within the genera Jonesia and Streptomyces have the potential to further degrade other petroleum-based polymers—natural or synthetic chains of molecules bound together.

The plastic-degrading microorganisms were sampled in May 2021 from Dafeng in eastern China, a UNESCO-protected site near the Yellow Sea Coast. The sampling confirmed the presence of a terrestrial plastisphere, a term that is relatively new to terrestrial ecology as past studies have primarily focused on marine environments. The microbiome of this "man-made ecological niche" of coastal plastic debris was further found to be distinct from the surrounding soil.

Scientists are increasingly looking at microorganisms, such as fungi and bacteria, to help tackle some of the most pressing challenges of the modern age, including the rising tide of plastic pollution. Researchers are hopeful that answers to this problem could be found in the plastisphere.

Past research has already recognized the potential of microorganisms to tackle plastic waste; a 2017 study led by researchers from China and Pakistan identified a strain of the fungi Aspergillus tubingensis that was breaking down plastic at a landfill in Islamabad, Pakistan. To date, 436  species of fungi and bacteria have been found to degrade plastic and Kew scientists and partners believe their latest findings could lead to the development of efficient enzymes designed to biologically degrade plastic waste.

Guan Pang et al, The distinct plastisphere microbiome in the terrestrial-marine ecotone is a reservoir for putative degraders of petroleum-based polymers, Journal of Hazardous Materials (2023). DOI: 10.1016/j.jhazmat.2023.131399

This New Plastic Disappears When You Don't Need It Anymore

The plastic that eats itself

Our reliance on plastic has become a huge problem, which is why researchers are excited about a new type of material – one that comes with built-in biodegrading capabilities, due to the bacterial spores living inside it. The new self-digesting plastic combines thermoplastic polyurethane (TPU) and Bacillus subtilis bacteria, which had to be engineered to survive the high temperatures involved in plastic production. By repeatedly exposing the spores to increasing levels of heat, the team of researchers behind this new work found that the bacteria could eventually cope with the temperatures of 135 degrees Celsius (275 degrees Fahrenheit) required to mix the bacterial spores and TPU together. Past efforts to find ways to degrade plastics, fast, have often sourced bacterial enzymes and fungi from soils and compost heaps where those microbes are naturally abundant. But this new material needs only the bacterial spores inside it, reawakened with some nutrients and moisture, to start breaking down.

https://www.nature.com/articles/s41467-024-47132-8

Study identifies fungus that breaks down ocean plastic

A fungus living in the sea can break down the plastic polyethylene, provided it has first been exposed to UV radiation from sunlight. Researchers published their results in the journal Science of the Total Environment. They expect that many more plastic degrading fungi are living in deeper parts of the ocean.

The fungus,  Parengyodontium album lives together with other marine microbes in thin layers on plastic litter in the ocean. Marine microbiologists from the Royal Netherlands Institute for Sea Research (NIOZ) discovered that the fungus is capable of breaking down particles of the plastic polyethylene (PE), the most abundant of all plastics that have ended up in the ocean.

The finding allows the fungus to join a very short list of plastic-degrading marine fungi: only four species have been found to date. A larger number of bacteria was already known to be able to degrade plastic.

The researchers went to find the plastic degrading microbes in the hotspots of plastic pollution in the North Pacific Ocean. From the plastic litter collected, they isolated the marine fungus by growing it in the laboratory, on special plastics that contain labeled carbon.

These so-called 13C isotopes remain traceable in the food chain. It is like a tag that enables us to follow where the carbon goes. We can then trace it in the degradation products.

What makes this research scientifically outstanding, is that we can quantify the degradation process." In the laboratory, researchers observed that the breakdown of PE by P. album occurs at a rate of about 0.05% per day.

The measurements also showed that the fungus doesn't use much of the carbon coming from the PE when breaking it down. Most of the PE that P. album uses is converted into carbon dioxide, which the fungus excretes again. Although CO2 is a greenhouse gas, this process is not something that might pose a new problem: the amount released by fungi is the same as the low amount humans release while breathing.

The presence of sunlight is essential for the fungus to use PE as an energy source, the researchers found.

A. Vaksmaa et al, Biodegradation of polyethylene by the marine fungus Parengyodontium album, Science of The Total Environment (2024). DOI: 10.1016/j.scitotenv.2024.172819

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