A waxworm, a moth larva that eats wax made by bees to build honeycomb, is seen in a laboratory in this undated handout photo obtained by Portal on October 4. New research shows that two enzymes in these worms’ saliva readily break down polyethylene. (Simona Gaddi, via Portal)
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WASHINGTON — Two substances in the saliva of waxworms — moth larvae that eat wax made by bees to build honeycomb — readily degrade a common type of plastic, researchers said Tuesday, marking a potential advance in the global fight against plastic pollution .
The researchers said the two enzymes identified in the caterpillar’s saliva rapidly and at room temperature break down polyethylene, the world’s most common plastic and a major contributor to an environmental crisis stretching from sea trenches to mountain peaks.
The study builds on the researchers’ 2017 findings that waxworms were able to break down polyethylene, although at the time it was unclear how these tiny insects did it. The answer was enzymes – substances produced by living organisms that trigger biochemical reactions.
For plastic to degrade, oxygen must penetrate the polymer – or plastic molecule – in an important first step called oxidation. The researchers found that the enzymes completed this step within hours without requiring any pre-treatment such as heat or irradiation.
This “changes the paradigm of plastic biodegradation,” said Spanish National Research Council molecular biologist Federica Bertocchini, who led the study, published in the journal Nature Communications.
Plastic is made from polymers that are persistent and contains additives that increase durability, allowing it to remain intact for years, decades, or centuries.
“The very same properties that make plastic the unique and useful material it is create one of the most critical problems of this century,” said Bertocchini.
“Plastics remain in the environment for a long time. They eventually break down into small particles, becoming the source of micro and nano plastic particles. These plastic particles have been found everywhere, from Antarctica to rainwater and tap water, which is not unique to them and causes obvious environmental problems, but is a growing human health concern,” Bertocchini added.
First produced in 1933, polyethylene is inexpensive, durable and does not interact with food, making it useful for food packaging and grocery bags, among other things.
Waxworms are the larvae of wax moths, a species called Galleria mellonella. Considered a pest by beekeepers, the caterpillars feed on beeswax, pollen and honey, and occasionally bee larvae.
The idea would be to synthetically produce the worms’ salivary enzymes, which the researchers have succeeded in doing to break down plastic waste. Bertocchini said using billions of waxworms to do the work has downsides, including producing carbon dioxide as they metabolize the polyethylene.
The same properties that make plastic the unique and useful material it is create one of the most critical problems of this century.
–Federica Bertocchini, molecular biologist
“In our case, the enzymes oxidize plastics and break them down into small molecules. This suggests alternative scenarios for dealing with plastic waste, in which plastics can be broken down under controlled conditions, limiting or eventually eliminating the release of microplastics,” said the fellow student. Author Clemente Fernandez Arias, ecologist and mathematician at CSIC.
A foundation associated with German plastics engineering company Röchling helped fund the research. Bertocchini is one of two heads of a Madrid-based company called Plasticentropy that is working to commercialize the use of enzymes to break down plastic waste.
The pursuit of biodegradation of plastics, or biodegradation, has so far focused primarily on microorganisms. A handful of microorganisms have been found to degrade plastic, but they do so only slowly and require pre-treatment, making it difficult to use in practice.
Plastic consumption has skyrocketed globally over the past three decades, with hundreds of millions of tons ending up as waste each year, with less than 10% being recycled.
The United Nations in March endorsed a landmark deal to create the world’s first global deal on plastic pollution, after talks in Nairobi, with a goal of finalizing a legally binding deal by 2024.
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