While companies around the world continue to innovate to find solutions to our ‘plastic problem’ — from creating biodegradable plant-based plastics to compete with their conventional counterparts to developing depolymerization processes to degrade said counterparts — another solution could exist in the belly of a worm.
A team of scientists at Beihang University in China have now discovered that bacteria from the guts of a common plastic-eating moth larva — which happily already enjoys snacking on food packaging — can degrade polyethylene, the type of plastic most commonly used in bags, bottles and other types of packaging. Reported in the ACS journal Environmental Science & Technology, the scientists say the finding could lead to new ways to help get rid of the otherwise persistent waste.
Environmental engineer Jun Yang, lead researcher on the study, points out that the global plastics industry churns out about 140 million tons of polyethylene every year, most of which is eventually discarded. Scientists have been trying to figure out for years how to make this plastic trash go away. Some recent studies have tried siccing bacteria on plastic to degrade it, but this required first exposing the plastic to light or heat.
Yang says his team wanted to find bacteria that could degrade polyethylene in one step, but that they found it by accident: One day, Yang was inspecting bags of millet in his kitchen and found them riddled with tiny holes. “I observed moths flying out of the bags and their larvae crawling around inside,” he told Chemical & Engineering News. He found that the larvae of Plodia interpunctella, or the Indian mealmoth — tiny grain-eating moth munching on stored food products in kitchens and grocery stores worldwide — might be digesting the plastic film with the help of bacteria in their stomachs.
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So Yang and his team extracted gut bacteria from the moth larvae and found that at least two strains of the microbes could degrade polyethylene without a pretreatment step. The researchers incubated the isolated species on small sheets of polyethylene. After 28 days, the sheets showed significant signs of degradation, pointing toward a new, more direct way to biodegrade plastic.
“Yang and his team are the first to provide detailed chemical evidence of bacterial degradation” of polyethylene, says Kenneth H. Nealson, an environmental microbiologist at the University of Southern California. “It has been nearly impossible to find an efficient way to degrade plastic,” he says.
The findings open the door to identifying plastic-degrading microorganisms in other insects, and creates opportunities to investigate how the chemical and biological properties of insect guts might boost the metabolism of plastics, Nealson said.