Wax worm saliva shown to degrade plastic bags in just hours

2022-10-04

The search for new solutions to the growing problem of plastic pollution has led scientists to some interesting places that include the soils of a Japanese recycling center and the guts of superworms. These efforts have unearthed enzymes that can eat away plastic materials with high efficiency, and scientists in Spain have just discovered more in the saliva of wax worms, which have the ability to degrade plastic bags in hours at room temperature.

The discovery of these enzymes stems from the work of Federica Bertocchini, a biology researcher and beekeeper in Spain who stumbled upon a peculiar ability of wax worms in 2017. These parasites feed on beeswax and, in an effort to shield her hives from destruction, Bertocchini placed plastic bags over them as protection.

Within 40 minutes, the bags were riddled with holes. Plastic bags are made of polyethylene, which accounts for around 29 percent of the world’s plastic consumption and is notoriously difficult to break down. That the worms took around 12 hours to turn the material into a gaping mess presenting some interesting possibilities, with follow-up experiments showing that the worms were actually digesting the plastic, rather than simply chewing through it.

But questions remained over how exactly this process was taking place, with the scientists looking to identify the mechanisms behind the worms’ ability to devour plastic. Which brings us to new research published this week that was led by Bertocchini and her team at the Biological Research Centre in Madrid.

The scientists used electron microscopy to analyze the saliva of the wax worms, and traced their appetite for plastic to a pair of enzymes. Within a few hours at room temperature, these enzymes worked together to create visible craters on the surface of the plastic and simultaneously oxidize the material. By working in tandem in this manner, the team sees the enzyme pair as a new weapon against plastic degradation, and one that has clear strengths over other enzymes with similar abilities.

“For plastic to degrade, oxygen must penetrate the polymer (the plastic molecule),” explained Bertocchini. “This is the first step in oxidation, which is usually a result of exposure to sunlight or high temperatures, and represents a bottleneck that slows down the degradation of plastics like polyethylene, one of the most resistant polymers. That is why, under normal environmental conditions, plastic takes months or even years to degrade. These enzymes that have been now discovered are the first and only known enzymes capable of degrading polyethylene plastic by oxidizing and breaking down the polymer very rapidly (after just a few hours of exposure) without requiring pre-treatment and work at room temperature.”

The scientists hope to carry out further work uncovering the mechanisms behind the enzymes’ ability to degrade plastics. They note there is much more work to be done, but hope the technology can one day help tackle to mounting problem of plastic contamination.

New Atlas, 4 October 2022
; https://newatlas.com