Wax worm saliva discovered as first animal-based plastic-degrading enzyme, according to researchers

All image credits: Simona Gaddi.

05 Oct 2022 --- Researchers at the Center for Biological Research (CIB) in Spain have discovered that the saliva of wax worm species contains enzymes that are able to degrade plastics. The discovery of these enzymes being able to rapidly set off PE opens a new window of hope for treating and recycling plastic waste.

PackagingInsights speaks to Dr. Federica Bertocchini, head of the research group, about the discovery and what role the findings could play in solving the global plastic pollution crisis.

“The field of biodegradation has represented a hope for a solution. However, to date nothing has been found to degrade sturdy polymers such as PE, polystyrene or PP, neither microorganisms nor enzymes. These are the first enzymes (and they happen to be from an animal), capable of doing that.”

“Considering that they work at room temperature in an aqueous solution, it makes it all easier.

What I envision is a situation in which plastic waste can be degraded in a controlled environment (such as a big container) and have a solution of these enzymes (lots of them) poured on top.”

“It might be a solution for plastic waste,” says Bertocchini.

The researchers discovered the “first and only” known enzymes capable of degrading PE plastic.Tough but not unbreakable
The researchers have found that the Demetra enzyme had a “significant effect” on PE, leaving marks (small craters) on the surface of the plastic visible to the naked eye. Additionally, degradation products are formed after exposure of the PE to this enzyme.

The Ceres enzyme oxidizes the polymer too but does not leave visible marks, suggesting that the two enzymes have a different effect on PE.

The researchers explain that PE is one of the toughest and most widely used plastics. Together with PP and polystyrene, it makes up 70% of total plastic production. Plastic pollution threatens the planet’s health and environment, and biodegradation by microorganisms such as bacteria and fungi is proposed as a possible solution to tackle the plastic waste problem.

Accelerating plastic degradation
To date, only a handful of microorganisms are known to break down the tough plastic polymers forming PE. In most cases, aggressive pre-treatment is needed to guarantee oxidation and thus enable the micro-organisms to exert some effect on the plastic.

“For plastic to degrade, oxygen must penetrate the polymer (the plastic molecule). 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 PE, one of the most resistant polymers,” explains Bertocchini.

“That is why, under normal environmental conditions, plastic takes months or even years to degrade,” she adds. These enzymes that have now been discovered are the “first and only” known enzymes capable of degrading PE plastic by oxidizing and breaking down the polymer rapidly (after just a few hours of exposure) without requiring pre-treatment and work at room temperature.

More research to follow
When asked how much time is required for the Demetra enzyme to degrade plastic, Bertocchini says that they don’t know that yet, but she highlights that they observe “a strong visual effect with Demetra after a few hours, and we know that increasing exposure increases the effect.”

Mechanisms by which these enzymes are able to degrade plastic are still unknown and more research combining insect biology with biotechnology is required.

“We need to optimize the enzymes, quantify the degradation and priority, and study the molecular mechanisms that allow these enzymes to oxidize PE. In parallel, we need to know what these enzymes do in vivo, and what is their role in the worm life cycle. Then there is the issue of trying other plastics (like PP, for example), and the scaling up,” concludes Bertocchini.

By Natalie Schwertheim

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