An article published in the journal “Microbial Genomics” reports the results of a study of the ability to digest polystyrene by the larvae of beetles belonging to the species Zophobas morio, commonly known as superworms, kingworms, or morio worms. A team of researchers from the Australian University of Queensland led by Chris Rinke used a metagenomic technique to analyze these larvae’s gut microbiome to find which microorganisms and in particular which genes are responsible for the digestion of polystyrene. The idea is to produce the enzymes needed to destroy the polystyrene waste in an ecological way.
The ability of superworm larvae (Photo ©André Karwath aka Aka) to digest polystyrene was discovered and described in two articles – available here and here – published in September 2015 in the journal “Environmental Science and Technology”. The superworms belong to the family of the darkling beetles (Tenebrionidae) and their larvae, as well as those of other darkling beetles, are farmed in many parts of the world as animal food and in some cases even as food for humans because their high content of protein and fat makes them very nutritious. The discovery of their peculiarity linked to the digestion of polystyrene has made the superworm larvae even more interesting.
When the first researchers realized that superworm larvae could digest polystyrene, the thought went to the possibility of eliminating the enormous amounts of this type of plastic that are thrown away every year in an environmentally clean way. In fact, recycling the various types of plastics is often difficult. However, even breeding enough superworm larvae to eat the discarded polystyrene is far more difficult than breeding the required amount as food. Some scientists conducted a targeted study to find the best solution.
The first phase of this new study focused on the feasibility of using superworm larvae to eliminate polystyrene. Tests showed that these larvae can survive on a diet based on this type of plastic but show negative changes in their gut microbiome, even with the emergence of pathogenic microorganisms. In order to hope to eliminate huge quantities of polystyrene, superworm larvae need to remain healthy. Adding other types of food to provide them with a balanced diet could help. These are assessments to be made after further targeted studies.
Another approach is given by metagenomics, which allows studying the microbiome of superworm larvae by sequencing the genome of the various microorganisms that make it up. This is a crucial step to precisely identifying the genetic origin of the digestion of polystyrene. In practice, it allows identifying which microorganism produces the enzyme or the combination of enzymes that breaks the polystyrene to pieces.
This part of the study provided some answers but still leaves questions because replicating a biochemical process that occurs in an animal’s intestinal tract is not easy. Finding out which enzyme or enzymes are needed is the first step but it’s necessary to understand under what conditions the reactions that lead to the elimination of polystyrene take place. The researchers intend to continue this type of study, and also to find solutions to eliminate other types of plastics. Achieving industrial biodegradation would be a major step forward, even more, if it were possible to generate useful compounds.