In a correspondence article published in the peer-reviewed journal Current Biology on April 24, 2017, Paolo Bombelli and colleagues from the Instituto de Biomedicina y Biotechnologia de Cantabria-CSIC-Universidad de Cantabria-SODERCAN, Santander, Spain, reported on the ability of wax moth larvae to biodegrade polyethylene (PE) into ethylene glycol. PE and the related plastic type polypropylene (PP) represent about 92% of total plastic production, and 80 million tons of PE alone are being produced every year worldwide. PE’s high stability results in its steady accumulation, polluting the environment.
The larvae of the wax moth Galleria mellonella are commonly found as parasites in bee colonies where they feed on wax. Now the authors showed that these “wax worms” are also able to produce “holes” in a PE film. Around 100 wax worms left in contact with a commercial PE shopping bag for 12 hours caused a mass loss of 92 milligrams PE. Furthermore, the scientists showed that a fresh preparation of dead worms, containing the still-functioning enzymes from their bodies or from microorganisms contained within, was also able to facilitate a reaction transforming the PE polymer into ethylene glycol chemical. The authors concluded that their findings “indicate chemical breakdown of the PE, including breakage of C-C bonds,” occurring at a “fast rate.”
Based on the preliminary results reported in Bombelli’s article, Elisabeth Pennisi, in her article published in Science magazine on April 24, 2017, concluded that this “caterpillar may be another solution” to the “[PE] recycling challenge.” The news on the “plastic-munching worms” were also widely covered in other media outlets, including ScienceDaily, Mail Online, CNN, The Guardian, EurekAlert, Plastics News, and EcoWatch, describing this discovery as a means to “save the Earth” in the “war on plastic waste.” However, an opinion article by Philip Ball, published by The Guardian on April 25, 2017, offered a less jubilant account of potential challenges to be overcome before these promises can be realized.
In particular, Ball pointed out that “you’d need an awful lot of wax moth caterpillars to make a significant dent on the plastic waste problem.” He also discussed the potential dangers to bee colonies that could result from cultivating large quantities of wax moths, their natural enemy. Further, Ball pointed out that the current breakthrough might not be as new, since already in 2014 another moth species, the Indian mealmoth (also called waxworm, Plodia interpunctella), was also found to possess an ability to break down the PE.
In that 2014 article by Jun Yang and colleagues from Beihang University, Beijing, China, the PE-degrading capacity was attributed to the bacteria residing in the gut of this caterpillar. Thus, PE degradation by wax moth larvae could also be due to bacteria. The same group showed that gut bacteria also play an essential role in the capacity to degrade another type of plastic, polystyrene, demonstrated by the larvae of mealworms Tenebrio molitor. Ball concluded that “those bacteria could provide the ideal solution,” as “they could be brewed up in fermentation vats that would dissolve plastics.” However, the practical implementation of this idea may still be years ahead.
Elizabeth Pennisi (April 24, 2017). “Could this caterpillar solve the world’s plastic bag problem?” Science Magazine
ScienceDaily (April 24, 2017). “Wax worm caterpillar will eat plastic shopping bags: New solution to plastic waste?”
Phoebe Weston (April 24, 2017). “A solution to plastic pollution? Amazing caterpillar could EAT its way through our waste bottles and bags.” Mail Online
AJ Willingham (April 24, 2017). “How a plastic-munching caterpillar could help save the earth.” CNN
EurekAlert! (April 24, 2017). “A plastic-eating caterpillar.”
Stern (April 24, 2017). “Diese Motte sagt dem größten Umweltproblem der heutigen Zeit den Kampf an.” (in German)
Ian Sample (April 25, 2017). “Plastic-eating worms could help wage war on waste.” The Guardian
Lorraine Chow (April 25, 2017). “This tiny caterpillar could help solve the world’s plastic crisis.” EcoWatch
James Vincent (April 26, 2017). “Plastic-eating caterpillars could help get rid of the world’s waste.” The Verge
Michael Lauzon (April 26, 2017). “Researchers study if caterpillar holds key to plastic litter.” Plastics News
Philip Ball (April 25, 2017). “Plastic-eating bugs? It’s a great story – but there’s a sting in the tail.” The Guardian
Bombelli, P., et al. (2017). “Polyethylene bio-degradation by caterpillars of the wax moth Galleria mellonella.” Current Biology 8:292-293.
Yang, J., et al. (2014). “Evidence of polyethylene biodegradation by bacterial strains from the guts of plastic-eating waxworms.” Environmental Science & Technology 48: 13776-13784.
Yang, Y., et al. (2015). “Biodegradation and mineralization of polystyrene by plastic-eating mealworms: Part 2. Role of gut microorganisms.” Environmental Science & Technology 49: 12087-12093.