In 2017, researchers at the Spanish National Research Council discovered that larvae
“We have carefully studied the behavior of the wax worm,when it comes into contact with polyethylene, and found that enzymes present in the worm's saliva (in the fluid in the insect's mouth) can degrade the polyethylene. Upon contact with saliva, the polymer oxidizes and depolymerizes within hours,” says Federica Bertocchini, head of the study.
Scientists analyzed saliva usingelectron microscopy and found in it both the remains of degraded plastic and a large amount of protein. After analyzing these proteins, the researchers identified two enzymes, Demetra and Ceres, that had an effect on polyethylene.
Researchers say these enzymesaffect plastic differently. Demetra leaves "craters" visible to the naked eye on the surface of the polyethylene film. The Ceres enzyme also oxidizes plastic, but leaves no visible residue. Moreover, both substances belong to the phenol oxidase family - enzymes that oxidize phenols.
The authors of the work explain that phenols, as a rule,used by plants to protect against insects. Phenoloxidants are an evolutionary response of insects. They produce such enzymes to neutralize the effects of phenols and safely feed on plants.
Phenols are also present in many plastic additives. Researchers believe these additives help the waxworms' saliva break down the plastic.
Scientists note that these substances arethe first and only known enzymes capable of degrading polyethylene without pretreatment. In most cases, for plastic to be broken down by living organisms, aggressive pre-treatment is necessary to ensure oxidation.
Cover photo: Cesar Hernandez Regal, CSIC
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