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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 ...

Meet the Worms that Eat Plastic
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

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.

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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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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