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Permalink Reply by Dr. Krishna Kumari Challa on October 2, 2015 at 7:46am

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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.

Permalink Reply by Dr. Krishna Kumari Challa on May 11, 2023 at 8:55am

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

Permalink Reply by Dr. Krishna Kumari Challa on May 19, 2023 at 10:22am

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

Permalink Reply by Dr. Krishna Kumari Challa on May 14, 2024 at 12:35pm

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

Permalink Reply by Dr. Krishna Kumari Challa on June 10, 2024 at 9:33am

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

Permalink Reply by Dr. Krishna Kumari Challa on October 4, 2024 at 10:16am

Wastewater bacteria can break down plastic for food, yielding new possibilities for cleaning up plastic waste

Researchers have long observed that a common family of environmental bacteria, Comamonadacae, grow on plastics littered throughout urban rivers and wastewater systems.

Now researchers have discovered how cells of a Comamonas bacterium are breaking down plastic for food. First, they chew the plastic into small pieces, called nanoplastics. Then, they secrete a specialized enzyme that breaks down the plastic even further. Finally, the bacteria use a ring of carbon atoms from the plastic as a food source, the researchers found.

The discovery opens new possibilities for developing bacteria-based engineering solutions to help clean up difficult-to-remove plastic waste, which pollutes drinking water and harms wildlife.

The study is published in the journal Environmental Science & Technology.

Mechanisms of polyethylene terephthalate pellet fragmentation into nanoplastics and assimilable carbons by wastewater Comamonas, Environmental Science & Technology (2024).

Permalink Reply by Dr. Krishna Kumari Challa on October 8, 2024 at 12:08pm

Plastic-eating enzyme identified in wastewater microbes

Plastic pollution is everywhere, and a good amount of it is composed of polyethylene terephthalate (PET). This polymer is used to make bottles, containers and even clothing. Now, researchers report in Environmental Science & Technology that they have discovered an enzyme that breaks apart PET in a rather unusual place: microbes living in sewage sludge. The enzyme could be used by wastewater treatment plants to break apart microplastic particles and upcycle plastic waste.

Microplastics are becoming increasingly prevalent in places ranging from remote oceans to inside bodies, so it shouldn't be a surprise that they appear in wastewater as well.

However, the particles are so tiny that they can slip through water treatment purification processes and end up in the effluent that is reintroduced to the environment. But effluent also contains microorganisms that like to eat those plastic particles, including Comamonas testosteroni—so named because it degrades sterols like testosterone.

Other bacterial species, including the common E. coli, have previously been engineered to turn plastic into other useful molecules. However, C. testosteroni naturally chews up polymers, such as those in laundry detergents, and terephthalate, a monomer building block of PET.

Researchers wanted to see if C. testosteroni could also produce enzymes that degrade the PET polymer.

The team incubated a strain of C. testosteroni with PET films and pellets. Although the microbes colonized both shapes, microscopy revealed that the microbes preferred the rougher surface of the pellets, breaking them down to a greater degree than the smooth films.

To better simulate conditions in wastewater environments, the researchers also added acetate, an ion commonly found in wastewater. When acetate was present, the number of bacterial colonies increased considerably.
Though C. testosteroni produced some nano-sized PET particles, it also completely degraded the polymer to its monomers—compounds that C. testosteroni and other environmental microbes can use as a source of carbon to grow and develop, or even convert into other useful molecules, according to the team.

Next, the researchers used protein analysis to identify the key enzyme that gives this microbe its plastic-eating abilities. Though this new enzyme was distinct from previously described PET-busting enzymes based on its overall protein sequence, it did contain a similar binding pocket that was responsible for PET breakdown.

When the gene encoding for this key enzyme was placed into a microbe that doesn't naturally degrade PET, the engineered microbe gained the ability to do so, proving the enzyme's functionality.

The researchers say that this work demonstrates C. testosteroni's utility for upcycling PET and PET-derived carbons, which could help reduce plastic pollution in wastewater.

 Rebecca A. Wilkes et al, Mechanisms of Polyethylene Terephthalate Pellet Fragmentation into Nanoplastics and Assimilable Carbons by Wastewater Comamonas, Environmental Science & Technology (2024). DOI: 10.1021/acs.est.4c06645

Permalink Reply by Dr. Krishna Kumari Challa on November 13, 2024 at 11:35am

Plastic-eating insect discovered in Kenya

by Fathiya Khamis

There's been an exciting new discovery in the fight against plastic pollution: mealworm larvae that are capable of consuming polystyrene. They join the ranks of a small group of insects that have been found to be capable of breaking the polluting plastic down, though this is the first time that an insect species native to Africa has been found to do this.

Polystyrene, commonly known as styrofoam, is a plastic material that's widely used in food, electronic and industrial packaging. It's difficult to break down and therefore durable. Traditional recycling methods—like chemical and thermal processing—are expensive and can create pollutants. This was one of the reasons we wanted to explore biological methods of managing this persistent waste.

I am part of a team of scientists from the International Centre of Insect Physiology and Ecology who have found that the larvae of the Kenyan lesser mealworm can chew through polystyrene and host bacteria in their guts that help break down the material. Our paper is published in the journal Scientific Reports.

The lesser mealworm is the larval form of the Alphitobius darkling beetle. The larval period lasts between 8 and 10 weeks. The lesser mealworm are mostly found in poultry rearing houses which are warm and can offer a constant food supply—ideal conditions for them to grow and reproduce.

Though lesser mealworms are thought to have originated in Africa, they can be found in many countries around the world. The species we identified in our study, however, could be a sub-species of the Alphitobius genus. We are conducting further investigation to confirm this possibility.

Our study also examined the insect's gut bacteria. We wanted to identify the bacterial communities that may support the plastic degradation process.

Plastic pollution levels are at critically high levels in some African countries. Though plastic waste is a major environmental issue globally, Africa faces a particular challenge due to high importation of plastic products, low re-use and a lack of recycling of these products.

By studying these natural "plastic-eaters", we hope to create new tools that help get rid of plastic waste faster and more efficiently. Instead of releasing a huge number of these insects into trash sites (which isn't practical), we can use the microbes and enzymes they produce in factories, landfills and cleanup sites. This means plastic waste can be tackled in a way that's easier to manage at a large scale.

Key findings

We carried out a trial lasting over a month. The larvae were fed either polystyrene alone, bran (a nutrient-dense food) alone, or a combination of polystyrene and bran.

We found that mealworms on the polystyrene-bran diet survived at higher rates than those fed on polystyrene alone. We also found that they consumed polystyrene more efficiently than those on a polystyrene-only diet. This highlights the benefits of ensuring the insects still had a nutrient-dense diet.

While the polystyrene-only diet did support the mealworms' survival, they didn't have enough nutrition to make them efficient in breaking down polystyrene. This finding reinforced the importance of a balanced diet for the insects to optimally consume and degrade plastic. The insects could be eating the polystyrene because it's mostly made up of carbon and hydrogen, which may provide them an energy source.

The mealworms on the polystyrene-bran diet were able to break down approximately 11.7% of the total polystyrene over the trial period.

Gut bacteria

The analysis of the mealworm gut revealed significant shifts in the bacterial composition depending on the diet. Understanding these shifts in bacterial composition is crucial because it reveals which microbes are actively involved in breaking down plastic. This will help us to isolate the specific bacteria and enzymes that can be harnessed for plastic degradation efforts.

The guts of polystyrene-fed larvae were found to contain higher levels of Proteobacteria and Firmicutes, bacteria that can adapt to various environments and break down a wide range of complex substances. Bacteria such as Kluyvera, Lactococcus, Citrobacter and Klebsiella were also particularly abundant and are known to produce enzymes capable of digesting synthetic plastics. The bacteria won't be harmful to the insect or to the environment when used at scale.

The abundance of bacteria indicates that they play a crucial role in breaking down the plastic. This may mean that mealworms may not naturally have the ability to eat plastic. Instead, when they start eating plastic, the bacteria in their guts might change to help break it down. Thus, the microbes in the mealworms' stomachs can adjust to unusual diets, like plastic.

These findings support our hypothesis that the gut of certain insects can enable plastic degradation. This is likely because the bacteria in their gut can produce enzymes that break down plastic polymers.

This raises the possibility of isolating these bacteria, and the enzymes produced, to create microbial solutions that will address plastic waste on a larger scale.

What's next

Certain insect species, such as yellow mealworms (Tenebrio molitor) and superworms (Zophobas morio), have already demonstrated the ability to consume plastics. They're able to break down materials like polystyrene with the help of bacteria in their gut.

Our research is unique because it focuses on insect species native to Africa, which have not been extensively studied in the context of plastic degradation.

This regional focus is important because the insects and environmental conditions in Africa may differ from those in other parts of the world, potentially offering new insights and practical solutions for plastic pollution in African settings.

The Kenyan lesser mealworm's ability to consume polystyrene suggests that it could play a role in natural waste reduction, especially for types of plastic that are resistant to conventional recycling methods.

Future studies could focus on isolating and identifying the specific bacterial strains involved in polystyrene degradation and examining their enzymes.

We hope to figure out if the enzymes can be produced at scale for recycling waste.

Additionally, we may explore other types of plastics to test the versatility of this insect for broader waste management applications.

Scaling up the use of the lesser mealworms for plastic degradation would also require strategies for ensuring insect health over prolonged plastic consumption, as well as evaluating the safety of resulting insect biomass for animal feeds.

Evalyne W. Ndotono et al, Mitogenomic profiling and gut microbial analysis of the newly identified polystyrene-consuming lesser mealworm in Kenya, Scientific Reports (2024). DOI: 10.1038/s41598-024-72201-9

This article is republished from THE CONVERSATION under a Creative Commons license. Read the original article.