Scientists Discover the Secret to Breaking Down Plastic: Beeswax-Eating Worms

National Geographic - Ocean Views    By Carl Safina (The Safina Center)   April 28, 2017

Federica Bertocchini is a developmental biologist at the University of Cantabria in Spain. Most days she can be found dressed in a white coat working on experiments in her lab. But in her spare time this scientist works in her backyard—wearing a protective suit, gloves and veil—tending to her bees.

Two years ago Bertocchini’s scientific work and beekeeping hobby collided into a major discovery. Like many beekeepers, Bertocchini must pluck pesky wax worms, a type of moth larvae that feed on beeswax and, if left to their own devices can munch through an entire hive. One day while de-worming her hives, she tossed the worms into an old grocery bag and left it outside. An hour later she picked up and inspected the bag and noticed small holes in the part where the worms were concentrated.

Waxworms. Photo by Wisconsin Department of Natural Resources (Flickr)

While Bertocchini is not a bug expert, she says her background in biochemistry led her to hypothesize that the worms were consuming the plastic bag, which was made of polyethylene—one of the most widely used types of plastics in the world.

“The characteristic chemical bond of polyethylene is also present in wax, although wax is made up of a different mix of molecules,” says Bertocchini.

Honey bees. Photo by PollyDot (Pixabay)Wax, like plastic, is a type of polymer, or substance made of a large number of the same type of molecule bonded together many times. Both wax and plastic are polymers held together with a string of linked carbon atoms, with other atoms attached to the sides. Because wax worms eat beeswax, Bertocchini thought maybe they contain some sort of specialized enzyme to break down its chemical bonds—and that same chemical may be capable of breaking down the bonds in plastic.

To find out, Bertocchini, with her University of Cantabria colleagues Paolo Bombelli and Christopher Howe, headed to their lab with worms and plastic. They placed 100 worms on samples of a polyethylene bag, watched and waited. They found that the worms created an average of 2.2 holes per hour in the plastic, and overnight consumed 92 milligrams of the bag. These statistics suggest it would take 100 worms one month to break down the average 5.5-gram polyethylene grocery bag. Their paper detailing this experiment was published this week in the journal Current Biology.

Trash, mostly plastic bags, in Karachi, Pakistan. Photo by Zainub Razvi (Flickr)

Polyethylene is the simplest of all commercially produced plastic polymers. Because all plastics have slightly different chemical makeups, could wax worms be capable of breaking down other varieties of plastic, such as polyvinyl chloride (used to make products like clear food packaging and shampoo bottles), polystyrene (used to make food trays and egg cartons) or polypropylene (used to make yogurt tubs and condiment bottles)?

“We do not know that yet, that is an interesting question, definitely worth studying,” says Bertocchini.

The scientists found it is indeed some sort of special chemical on or inside worms that breaks down the polyethylene, and is not just the chewing action of the worms’ jaws that break the plastic down. They determined this by spreading mashed-up dead worms on the plastic and watching the plastic break down before their eyes. It could be an enzyme inside of the worms, or perhaps a certain kind of bacteria in or on the worms’ bodies, that breaks down the plastic—more research is needed to determine which. While the precise aspect of the worms’ biology responsible for breaking down polyethylene remains unknown, the scientists say it converted the plastic into ethylene glycol, a type of moderately toxic chemical used in antifreeze.

Waxworm. Photo by USGS Bee Inventory and Monitoring Lab (Flickr)

Despite the challenges of degrading plastic on a large scale, Bertocchini says the knowledge that wax worms are capable of breaking down plastic could prove extremely valuable in the future. Each year the world produces about 300 million tons of plastic, with 8 million tons of that plastic entering the oceans and millions of tons more being littered on land or dumped into landfills. People wouldn’t sprinkle wax worms over piles of polyethylene, says Bertocchini, but apply the special plastic-degrading chemicals the worms contain.

“The idea would be to isolate the molecules responsible for the biodegradation, produce them in large industrial scale, and then apply that tool to biodegrade polyethylene,” Bertocchini says.

Dolphin caught on plastic bag in Fernando de Noronha, off Brazil’s coast. Photo by Jedimentat44 (Flickr)Whether or not wax-worm solvents will be developed and mass-produced in the future is yet to be seen. Perhaps it could help get rid of some of the world’s plastic. But, experts say, getting rid of plastic is only one aspect of remediating the world’s plastic problem. The best way to cut down on the pollution is to stop producing and using plastic products.

http://voices.nationalgeographic.com/2017/04/28/scientists-discover-the-secret-to-breaking-down-plastic-beeswax-eating-worms/

This Bug Can Eat Plastic. But Can It Clean Up Our Mess?

National Geographic    By Carrie Arnold    April 24, 2017

Scientists have discovered that wax worms can eat plastic bags. Could that help us reduce plastic pollution?

BY CARRIE ARNOLD

PHOTOGRAPH BY JONATHAN PLANT, ALAMY

Wax worms are common insects that evolved to live in bee hives. Now we know they can eat plastic. PHOTOGRAPH BY JONATHAN PLANT, ALAMY

Each year, the world produces 300 million tons of plastic, much of which resists degradation and ends up polluting every corner of the globe. But a team of European scientists may have found a unique solution to the plastic problem. They discovered that a common insect can chew sizable holes in a plastic shopping bag within 40 minutes.

“This study is another milestone discovery for the research on biodegradation of plastics,” says Wei-Min Wu, an environmental engineer at Stanford University.

The discovery was led by Federica Bertocchini, a developmental biologist at the University of Cantabria in Spain. She first noticed the possibility as she cleaned out her backyard bee hives two years ago.

She removed some wax worms (Galleria mellonella) living in the hive and placed them in an old plastic bag. When she checked the bag an hour later, however, she discovered small holes in the part of the bag with the larvae. Although Bertocchini wasn’t an entomologist, she guessed immediately what was happening.

The worms live in honeycombs, where they feed on wax. PHOTOGRAPH BY AGENCJA FOTOGRAFICZNA CARO, ALAMY

The larval form of a small moth, wax worms get their names because they live on the wax in bee hives. Like plastic, wax is a polymer, which consists of a long string of carbon atoms held together, with other atoms branching off the sides of the chain. Both wax and the polyethylene in Bertocchini’s plastic bag had a similar carbon backbone.

“Since they eat wax, they may have evolved a molecule to break it down, and that molecule might also work on plastic,” Bertocchini said.

SOLVING THE MYSTERY

Bertocchini teamed up with fellow scientists Paolo Bombelli and Christopher Howe to figure out how the wax worms were pigging out on plastic.

When they placed the worms on polyethylene plastic, they found that each worm created an average of 2.2 holes per hour. Overnight, 100 wax worms degraded 92 milligrams of a plastic shopping bag. At this rate, it would take these same 100 worms nearly a month to completely break down an average, 5.5 gram plastic bag.

WHICH INSECT EATS AND RECYCLES PLASTIC?

To rule out munching action from their jaws as the source of degradation, the team applied a soupy blend of recently deceased worms to the plastic and waited. Sure enough, they found the liquid larvae could also eat holes in plastic. This told Bertocchini and colleagues that an enzyme in the worms or the bacteria living in and on their bodies was dissolving the plastic.

That enzyme converted polyethylene into ethylene glycol, a chemical commonly used in antifreeze. Bertocchini hopes to identify the precise enzymes that break down polyethylene in future work.

SEARCHING FOR A SOLUTION

Scientists have searched for a way to biodegrade plastics for decades, says Uwe Bornscheuer, a biochemist at the University of Greifswald in Germany.

“Plastic pollution is a big global problem,” Bornscheuer said.

In 2014, Wu and colleagues at Stanford University found that a gut bacterium in another species of wax worm could break down polyethylene, although it had different byproducts. A 2016 study identified the enzymes in a species of bacteria that could break down a type of plastic called poly(ethylene terephthalate).

“There are probably lots of other worm species out there that can degrade plastics,” he said.

 

Wax worms are the larval stage of a type of moth. They are commonly fed to pet lizards. PHOTOGRAPH BY DAVID LIITTSCHWAGER, NATIONAL GEOGRAPHIC CREATIVETo marine biologist Tracy Mincer at the Woods Hole Oceanographic Institute, the solution to plastic pollution needs to focus on producing less and recycling more.

“Polyethylene is a high-quality resin that can be up-cycled in many ways and can fetch up to $500 per tonne,” he said in an email. “In my opinion, although this is an amazing natural history story and wonderful academic exercise, it is not a solution for disposing of polyethylene as this is throwing away money.”

http://news.nationalgeographic.com/2017/04/wax-worms-eat-plastic-polyethylene-trash-pollution-cleanup/

Stubborn Plastic May Have Met Its Match: The Hungry Wax Worm

Los Angeles Daily News/Science Section    By Amina Kahn     April 24, 2017

Here’s a caterpillar that thinks plastic tastes fantastic. Scientists have discovered that the larvae of the wax moth will easily munch through a common plastic known as polyethylene, turning it into a useful compound found in all kinds of consumer products.

The findings, published this week in the journal Current Biology, reveal an unlikely ally in the fight to reduce and reuse the enormous amounts of plastic waste that humans produce every year.

Plastic, made from oil, is the product of fossil fuels. Roughly 92% of it falls into two main categories: polyethylene and polypropylene. According to the study authors, polyethylene is widely used for packaging and so makes up about two-fifths of the plastic product demand.

Some of that plastic is recycled, but not much — out of 33.25 million tons of plastic generated in 2014, just 9.5% in the United States was recycled, according to the Environmental Protection Agency. An additional 15% was burned for energy, which is not the cleanest process, and the remaining 75.5% ended up in landfills.

“New solutions for plastic degradation are urgently needed,” the study authors wrote.

The problem is that such plastics are difficult to break down, said study coauthor Christopher J. Howe, a biochemist at Cambridge University in England. Polyethylene molecules have straight backbones of linked carbon atoms whose bonds are very stable. This means plastic doesn’t biodegrade easily in landfills, and it can form garbage patches in the ocean that pose deadly threats to marine wildlife.

Scientists have come across a few modest instances of polyethylene biodegradation, but they’re slow going. Researchers got a liquid culture of Penicillium simplicissimum fungus to break down some polyethylene — but it took three months. A bacterium, Nocardia asteroides, took four to seven months. Both appeared to produce ethylene glycol, a compound used in all kinds of products, including brake fluid, paints, plastics and even cosmetics.

This new study of the wax moth Galleria mellonella, an insect that inhabits bee hives and other places, changes that.

The discovery was something of a happy accident, Howe said: Lead author Federica Bertocchini, a developmental biologist at Institute of Biomedicine and Biotechnology of Cantabria in Spain, is a beekeper as well as a scientist. It was Bertocchini who noticed that if hive material containing moth larvae was wrapped in plastic bags, the caterpillars appeared to degrade tough plastic.

That may look like a leaf, but the wax worm is actually chewing through polyethylene plastic. (Federica Bertocchini, Paolo Bombelli and Chris Howe)Could these little caterpillars really do something that few critters are known to do?

To find out, the researchers set wax worms loose on a polyethylene film. They watched as holes appeared after just 40 minutes — at an estimated rate of about 2.2 holes per worm per hour. And when the researchers put roughly 100 wax moth larvae on a commercial shopping bag, they ate a total of 92 milligrams in about 12 hours.

Still, it was possible these wax worms were simply munching up material rather than actually digesting it into simpler products. So the scientists made a slurry of some worms and smeared the dissociated cells on polyethylene films. After 14 hours, the researchers found that 13% of the polyethylene mass had been lost — a degradation rate of 0.23 of a milligram per square centimeter.

When the researchers examined what remained of the slurry-coated plastic film, they found a signature that indicated the presence of that oh-so-useful compound, ethylene glycol — a sign that the caterpillar cells really had broken the plastic down.

How does the wax worm manage such a difficult feat, and do it with such incredible speed? It’s all thanks to the natural diet of this caterpillar, which makes its home within the honeycomb.

It’s “probably because the beeswax in the hives is similar chemically to the plastic,” Howe said. “The larvae have evolved to be able to break down the beeswax, and can break down plastic as well, given the chemical similarity.”

Beeswax is made of a wide variety of compounds, including alkanes, alkenes, fatty acids and esters. Many of those compounds include those carbon-carbon bonds — which could mean the wax moth has a natural talent for breaking those down.

So far, the scientists are not sure whether this ability is due to the wax moth larva, or to the microbes within its gut. An earlier study by a different group found that two bacterial strains taken from the gut of the Indian mealmoth could break down plastic in a few weeks (though the authors did not report seeing any ethylene glycol production).

Finding out which critter is responsible is one of the next steps in the research, Howe said.

“In the long term we'd like to use this as a basis for breaking down waste polyethylene — but there are many hurdles to be overcome in scaling the process up,” he said. “We would probably try to find the gene(s) for the enzyme(s) that are responsible, and use the gene to make lots of the enzyme in a biotechnological process rather than growing large numbers of the caterpillars.”

http://www.latimes.com/science/sciencenow/la-sci-sn-worm-eats-plastic-20170424-story.html

It's National Moth Week!

Bug Squad - Happenings in the Insect World   By Kathy Keatley Garvey   July 23, 2014  

The event, which runs through Sunday, celebrates "the beauty, life cycles, and habitats of moths," according to its website. Scientists and citizen scientists are encouraged to document their findings. It's now a worldwide event.

A few nuggets from the website:

"Moths are among the most diverse and successful organisms on earth.

  • Scientists estimate there are 150,000 to more than 500,000 moth species.
  • Their colors and patterns are either dazzling or so cryptic that they define camouflage. Shapes and sizes span the gamut from as small as a pinhead to as large as an adult's hand.
  • Most moths are nocturnal, and need to be sought at night to be seen – others fly like butterflies during the day.
  • Finding moths can be as simple as leaving a porch light on and checking it after dark. Serious moth aficionados use special lights and baits to attract them."

Then there are, of course, the pests such as the greater wax moth, Galleria mellonella. This moth slips in at night to honey bee colonies and lays its eggs. The bees struggle to remove the larvae.  Beekeepers struggle with control of the  tell-tale evidence--damaged combs.

The honey bee bible, The Hive and the Honey Bee (Dadant Publication), says the wax moth female "produces less than 300 eggs during her life span of 3 to 30 days, but a few lay as many as 2000 eggs. Mated females fly to beehives one to three hours after dark, enter, and lay eggs until they leave shortly before daylight."

Sneaky little critters!

The Hive and the Honey Bee authors relate that "the presence of the wax moth larvae usually signals a major problem such as queenlessness, an infectious disease, poisoning and starvation."

Greater wax moths are probably not what the organizers of National Moth Week, founded by two naturalists in East Brunswick, N.J., had in mind when they launched this special week! (Unless, of course, they were anglers; the larvae make good fish bait!)

 Read at: http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=14760