The Spanish National Research Council.

Wax worm saliva contains enzymes capable of breaking down plastics
Credit: César Hernández Regal

A team of CSIC researchers discovered that wax worm saliva degrades plastic and that it can be used to treat or recycle plastic waste. The lepidopteran Galleria mellonella was discovered to be able to break down plastic by using its saliva, and now they have discovered how it does this. Federica Bertocchini, a CSIC researcher, led the study which found that the first and only known enzymes capable of degrading polyethylene plastic without requiring pre-treatment. The results of the work have been published in the online archive.

Oxygen must penetrate the plastic molecule to degrade it. This is the first step in oxidation, which is usually a result of exposure to sunlight or high temperatures, and represents a roadblock that slows down the degradation of plastics like polyethylene, one of the most resistant polymers.

The wax worm's saliva oxidizes the plastic. She says that this means they can speed up the plastic degradation process.

One of the toughest and most widely used plastic is polyethylene. It makes up 70% of plastic production. The plastic waste problem poses a threat to the environment and the health of the planet. The biological degradation of plastics is one of the most promising research areas. The process of biodegradation is associated with a number of organisms. Only a few organisms are known to break down the tough plastic. Aggressive pre-treatment is needed to guarantee oxidation and allow the micro-organisms to exert some effect on the plastic.

worms eat plastic

A few years ago, a new field of research opened up with the discovery that some insect species are able to degrade.

In recent years, efforts have been made to find out how these insects manage to do this.

The wax worm's behavior when it comes into contact with polyethylene has been scrutinized and it has been found that the saliva of the worm can degrade the substance. She says that they have identified degraded residues that form in the saliva of the worm.

The saliva was analyzed using electron microscopy and the researchers found a high amount of proteins. The family of phenol oxidase enzymes has two proteins called Demetra and Ceres.

The appearance of degradation products on the surface of the plastic was confirmed by the appearance of marks on the surface of the plastic. She says that the two enzymes have a different effect on the same material.

How phenol oxidase works.

Plants use pheols to defend themselves against potential enemies. If insects could oxidize plant phenols, they would be able to feed on the plants. It is possible that phenols could make them targets for the enzymes and create the conditions for oxidation and depolymerisation of the plastic.

How wax worms have been able to do this is an interesting question. It could be due to an evolutionary process. There are a lot of plant species that feed on hive wax and pollen. These bugs would be very useful if this type of enzyme was used. This would explain why wax worms break down. We need to carry out more research combining insect biology with technology.

More information: Federica Bertocchini et al, Wax worm saliva and the enzymes therein are the key to polyethylene degradation by Galleria mellonella, BioRxiv (2022) DOI: 10.1101/2022.04.08.487620v1 Provided by Spanish National Research Council (CSIC) Citation: Wax worm saliva contains enzymes capable of breaking down plastics (2022, May 24) retrieved 24 May 2022 from This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.