Researchers have discovered that two substances found in the saliva of waxworms — moth larvae, which eat honeycomb wax — can readily dissolve common plastic. This is a significant step in the fight against plastic pollution.
Researchers discovered that two enzymes found in caterpillar saliva degrade polyethylene quickly and at room temperature. This plastic is the most widely used and significant contributor to the environmental crisis that has swept from the ocean trenches to the mountaintops.
This study expands on 2017 research that showed wax worms could degrade polyethylene. However, it was not clear how they did it. Enzymes — substances that are produced by living organisms and trigger biochemical reactions — were the answer.
The first step in plastic’s degrading process is oxidation. This involves oxygen entering the polymer (or plastic molecule) through an important initial step. Researchers found that enzymes could perform this step in just hours, without any pretreatment like heat or radiation.
Federica Bertocchini, a molecular biologist from the Spanish National Research Council (CSIC), led the study that was published in Nature Communications.
Plastic is made from polymers that are hard to break down. It also contains additives that improve durability so it can last for many years, decades, or even centuries.
Bertocchini stated that plastic is a unique and valuable material. However, it also has the potential to create a major problem in the future.
“Plastics can stay in the environment for long periods. It eventually breaks down into smaller particles which can then be used to make micro- and nano-plastic particles. These plastic particles can be found all over the globe, including in rain, tap water, and Antarctica. They are not only a problem for the environment, but also pose a serious threat to human health,” Bertocchini said.
Polyethylene was first developed in 1933. It is durable, inexpensive, and doesn’t react with food. This makes it ideal for grocery bags and food packaging.
The larvae of Galleria mellonella wax moths are called wax worms. Caterpillars are considered pests by beekeepers. They eat honey, pollen, and beeswax. Sometimes, they also eat bee larvae.
It was possible to synthesize the saliva enzymes of the worms, as the researchers were able to do, to break down plastic waste. Bertocchini stated that the use of billions upon billions of waxworms to accomplish the task has its drawbacks, including the generation of carbon dioxide as they metabolize polyethylene.
“In our case, the enzymes react with plastics to oxidize them, breaking them down into smaller molecules. This opens up new ways to deal with plastic waste. Plastics can be controlled in controlled conditions, which limits or eliminates the release of microplastics,” explained Clemente Fernandez Arias (a CSIC ecologist and mathematician).
The research was funded by a foundation that is related to the German plastics engineering firm Rochling. Bertocchini is the leader of Plasticentropy, a Madrid-based company that works to commercialize the enzymes used to break down plastic waste.
The search for plastic degradation through biological means (or biodegradation) was previously dominated by microorganisms. Only a few microorganisms could break down plastic, but they were slow and required pre-treatment. This makes it difficult to harness it.
Over the last three decades, plastic consumption has skyrocketed worldwide. Hundreds of millions of tonnes of plastic end up as trash every year and less than 10% are recycled.
After talks in Nairobi, the United Nations approved in March a landmark agreement that would create the first-ever global plastic pollution treaty. The goal is to have a legally binding agreement in place by 2024.