Experts from St. Petersburg State Electrotechnical University LETI discovered that Zophobas morio larvae are able to completely break down the benzene rings that make up expanded polystyrene (foam). LETI told socialbites.ca about this.
One of the most promising ways to get rid of plastic is its destruction as a result of the activity of living organisms. Scientists wanted to check how effectively the larvae of Zophobas morio beetles cope with this task, but during experiments they discovered that they can not only absorb plastic, but also recycle it.
When members of Zophobas morio are in close contact with each other, they do not pupate, which is an evolutionary defense mechanism against cannibalism. So, if the population density is high enough, you can work with them for a relatively long time – Zophobas morio can remain in the caterpillar stage for 3-4 months until its natural end.
During the experiment, insects were divided into three groups. The first group was the control group; larvae ate grains, fruits and vegetables; their diet contained all the substances they needed to maintain normal life functions. The second group ate only polystyrene foam, and the third group received no food at all. Then, over the course of a month, the researchers regularly counted the number of surviving individuals in each group and also weighed polystyrene foam samples.
“In the well-fed control group, both dead individuals and exuviae (that is, the chitin membrane that caterpillars shed when moulting) remained virtually intact. The second group, Zophobas morio, resorted to cannibalism when it could not get all the nutrients it needed to survive from plastic. In the third group, cases of cannibalism occurred twice as often as in the second group,” the author of the study, Natalya Bereznikova, told socialbites.ca.
Next, the authors examined the plastic itself and the caterpillar feces using Fourier transform infrared spectroscopy. Since the main component of this material is the benzene ring, when obtaining the spectrum of the starting material, the researchers found distinct peaks that are characteristic of the benzene ring. However, such peaks were not found in the fecal spectrum of these plastic-fed larvae.
“So Zophobas morio not only transforms polystyrene foam, but also breaks down the benzene ring. It should be understood that the enzymes secreted by the bacteria in their digestive tract, not the larvae, are responsible for the digestion of plastic. The interest is in understanding what this group of bacteria is, isolating them and recreating the environment in which they will settle, i.e. is to create a bioreactor,” Bereznikova concluded.
In the future, scientists plan to continue their research with other types of plastic, especially polyethylene and ethylene vinyl acetate.
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