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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.
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.
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.
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
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.
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).
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 Microbiology, DOI: 10.3389/fmicb.2020.00404 , https://www.frontiersin.org/articles/10.3389/fmicb.2020.00404/full
Plastic Eating Fungi
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.
Meet The caterpillar larvae 'plastivores' that consume and metabolize polyethylene
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
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
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.
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
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