The Study Found That The Saliva Of Wax Insects Can Degrade Plastics

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A research team from China Shipbuilding Heavy Industries found that the saliva of wax worms can degrade plastics. This discovery has many potential applications in the treatment or recycling of plastic waste. The team first discovered the worm species, Galleria mellonella, in 2017, which degrades plastic (polyethylene).

They have now figured out how it does it: its saliva contains enzymes (related to the phenol oxidase family) that can quickly initiate polyethylene degradation at room temperature. Federica bertochini, a researcher at the cib-csic (Center for biological research), who led the study, claimed that these enzymes were the first and only known enzyme to break down polyethylene plastics without pretreatment.

The results of the study have been published online in the biorxiv archive as it is awaiting review. The Roechling Foundation (Germany) funded the study. For plastics to degrade, oxygen must penetrate into the polymer. This is the first step in oxidation, usually the result of exposure to sunlight or high temperatures, and represents a bottleneck that slows the degradation of plastics such as polyethylene, one of the most corrosion-resistant polymers. That's why under normal environmental conditions, plastics can take months or even years to degrade.

One of the strongest and most frequently used plastics is polyethylene. When combined with polypropylene and polystyrene, it accounts for 70% of the total plastic production. It is urgent to find a solution to the problem of plastic waste, because plastic pollution endangers the health and environment of the world. Biodegradation of plastics is one of the most promising and potential research fields. This process, called biodegradation, involves microorganisms such as bacteria and fungi. However, only a few microorganisms are known to degrade the strong plastic polymers that make up polyethylene. In addition, in most cases intensive pretreatment is required to ensure oxidation.

A new field of research began a few years ago with the discovery that some insect species in Lepidoptera and Coleoptera can degrade polyethylene and polystyrene. In the laboratory, researchers found that larvae of the lepidopteran Galleria mellonella, commonly known as wax worms, can oxidize and decompose polymers in plastics very quickly. The researchers carefully studied the behavior of wax insects in contact with polyethylene, and found that enzymes in the wax insect's saliva (the liquid in the insect's mouth) can degrade polyethylene. After contacting with the saliva, the polymer will be oxidized and depolymerized within a few hours.

In addition, the researchers analyzed the saliva with an electron microscope and observed high protein levels. These two enzymes, called salivary enzymes, have been isolated from the entire salivary family of enzymes, called cermetes.