Wax worms capable of degrading plastic! The discovery, published in NatureCommunications, is revolutionary! It could change the way plastics are recycled. Scientists from the Margarita Salas Biological Research Center in Madrid, Spain have just made a discovery, somewhat by chance. They observed that a small worm, capable of causing great damage in hives, could produce an enzyme that degrades plastics.
Waxworms chemically degrade polyethylene
Doctor Federica Bertocchini cleaned her hives, infested with these wax worms. He put them in polythene plastic bags. He then noticed that the insect was starting to make holes in these bags.
Looking more closely, the scientist very quickly realized that the wax worm Gallery mellonella was not content to pierce the plastic of the bags by a chewing action. In reality, there was a real chemical degradation of the plastic.
Polyethylene is a plastic material resulting from the transformation of petroleum. It is made by polymerizing ethylene, another chemical compound. We use this plastic a lot. The latter alone accounts for 30% of global plastics production.
There are different grades of polyethylene on the market. These are low density, high density and linear low density polyethylene. Low density polyethylene and linear polyethylene are used to manufacture flexible products such as films and pipes. High density polyethylene is used to make rigid products. Polyethylene is used in the manufacture of at least half of the packaging. It is also used to make flasks and bottles, flexible containers and also sports equipment.
Unfortunately, like many of its plastic counterparts, polyethylene accumulates in nature. Furthermore, current polyethylene recycling techniques are very energy-intensive and emit greenhouse gases. Products from recycling are also of lower quality.
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An enzyme that works at room temperature
Called wax moth, Gallery mellonella is a moth that lives in Europe. From May to October, it turns into a small butterfly with a wingspan of 3 to 4 centimeters. It is not the butterfly that causes problems, but the larva, which is called the wax worm. It destroys the hives by feeding on the wax that makes up the combs. These have a hexagonal shape. They are used by bees to store food, such as honey and pollen. They also serve to protect future bees in the form of eggs, larvae and pupae. To protect their hive, some beekeepers do not hesitate to favor the presence of the European hornet which feeds preferably on this moth.
By examining the larvae of Galleria mellonella in their laboratories, the researchers realized that they manufacture an enzyme secreted in their saliva which degrades polyethylene. It works at room temperature and at neutral pH by oxidizing and depolymerizing polyethylene in a few hours.
According to the researchers, the breakdown of polyethylene using this enzyme could produce new valuable secondary substances. Moreover, this enzyme could be produced quite easily in the laboratory, by chemical synthesis.
Before considering commercial use, researchers still need to improve it and think about the practical implementation of the system. They think of creating factories dedicated to the recycling of polyethylene by this method. They are also thinking of marketing, one day perhaps, kits that can be used at home to recycle their own polyethylene waste.
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Other enzymes capable of digesting plastics
This is not the first time that scientists have discovered bacterial enzymes that can be used to break down plastic materials. In 2021, a study had demonstrated the existence of 30,000 enzymes capable of degrading around ten different plastics.
In 2020, an enzyme that breaks down polyethylene terephthalate (PET) is discovered in bacteria that live in the soil amid decaying leaf litter. Other examples exist like this insect capable of feeding on polyurethane.
Plastic pollution is a real global scourge. In fact, millions of tonnes are produced each year and an equally large quantity ends up in nature. The latest studies estimate, for example, that every year between 25 million and 35 million tonnes of plastic end up in the seas and oceans. This pollution affects marine species in many ways. The latter can ingest microparticles, be exposed to chemical substances present in plastics or even find themselves stuck in plastics abandoned in the open sea such as fishing nets.
Researchers really don’t know why this enzyme degrades polyethylene. Some think that substances produced by plants to defend themselves would be similar to certain additives contained in plastics and that waxworms would be accustomed to encountering these products.
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