New Research Shows Waxworm's Saliva Degrades Polyethylene

A team of researchers from the CSIC has discovered that the saliva of the waxworm degrades plastic, which could have numerous applications in the treatment or recycling of plastic waste.

Enzymatic Degradation of Plastic:

The team discovered in 2017 that this species of worm (Lepidoptera Galleria mellonella) is capable of breaking down plastic (polyethylene), and now they have discovered it does so with their saliva containing enzymes (from the phenoloxidase family) that initiate the degradation of polyethylene in a short time and at room temperature.

"To degrade the plastic it is necessary that oxygen penetrates the polymer (into the plastic molecule)," explains Federica Bertocchini CSIC researcher at the Center for Biological Research (CIB-CSIC) who directed the study.

"This first step of oxidation, which is usually the result of exposure to sunlight or high temperatures, is a bottleneck that slows down the degradation of plastics such as polyethylene, one of the most resistant. Therefore, under normal environmental conditions, plastic takes months or years to degrade," explains Bertocchini.

These enzymes are the first and only ones known to be able to degrade polyethylene plastic without pre-treatment, according to Bertocchini. "We have now discovered that enzymes from waxworm saliva perform this crucial step: they oxidize plastic. Thus, they allow to overcome the bottleneck of plastic degradation and accelerate its decomposition,” further adds Bertocchini.

Polyethylene is one of the most resistant and used plastics. Together with polypropylene and polystyrene, they make up 70% of the total production of plastics. Plastic pollution poses a threat to the health and environment of the planet, so it is urgent to find solutions to deal with plastic waste.

Waxworm’s Plastic-eating Ability

An interesting question is to find out how wax insects acquired this ability. The researchers venture that it could be due to an evolutionary process. Waxworms feed on beehive wax and pollen from very diverse plant species. If you consider that the wax of hives is full of phenols, this type of enzyme would be very useful for worms. Indirectly, this would explain why waxworms can break down polyethylene. However, so far this theory is only speculation, and more studies combining insect biology with biotechnology will be needed.

Source: CSIC