Break down of plastic by superworms: analysis of their feces and gut bacteria
Plastic pollution is a global problem with the largest percentage of plastic wastes being disposed of in landfills. Innovative solutions are needed to deal with plastic wastes.
Researchers at Concordia University of Edmonton (Alberta, Canada) investigated the consumption and breakdown of a type of plastic, expanded polystyrene (EPS), by larvae of darkling beetles, often referred to as superworms (Zophobas morio or Zophobas atratus).
The study involved feeding the superworms to one of three diets; wheat bran, EPS white plastic blocks (used in packaging fragile equipment such as electronic devices), or EPS white plastic S-shaped chips (packing peanuts).
Read this open access paper on the FACETS website.
The EPS block and chips used were either exposed to ultraviolet (UV) radiation for 60 seconds or not exposed to UV radiation before being fed to superworms. The amount of original mass of plastic lost was mainly due to consumption by superworms and this was measured every week over a 28-day period.
The nitrogen and phosphorus content in the feces (or frass) of superworms, other products of plastic breakdown in the feces (or frass) of superworms, and gut bacteria composition were determined.
Over the 28-day period of the study the EPS white plastic blocks lost more than one-third of their original mass mainly due to consumption. However, S-shaped plastic chips lost approximately one-quarter of their original mass. Small quantities of nitrogen and phosphorus were found in the feces of superworms that fed on a plastic diet, but they were lower than those from wheat bran-fed superworms.
Twenty-one organic compounds were products of plastic breakdown identified in the feces of superworms, with most of them being able to dissolve in water and therefore are likely to break down further without difficulty. Some organic compounds identified contained nitrogen and phosphorus.
The study also identified a species of bacteria known as Pseudomonas aeruginosa from guts of superworms and this bacterium is known to break downplastic.
Stenotrophomonas sp. bacteria was also identified and is known to convert nitrogen in air for its use and to convert phosphorus into a form that dissolves in water easier.
Overall, the study showed that superworms have the potential to break down plastic wastes. However, more research is needed to determine the optimal conditions for superworms to degrade plastics and whether adult beetles that break down plastics stay healthy and able to reproduce.
Read the paper — Superworm (Coleoptera: Tenebrionidae, Zophobas morio) degradation of UV-pretreated expanded polystyrene by Emmanuel Mapfumo, Deborah Hemmerling, Cecilia Bukutu, Sachin Acharya, Emma Paterson, Seth Nobert, Megan MacElheren, and Makan Golizeh.
