The larval gut microbiota of Hermetia illucens can contribute to the development of promising strategies to solve plastic pandemics

Plastic accumulation in the environment represents a global concern, dramatically impacting ecosystems, as the physicochemical characteristics of plastic polymers make them exceptionally persistent and inaccessible to most natural enzymes. However, bacterial and fungal species isolated from disparate sources, such as marine ecosystems, soil, plastic landfills, and even invertebrate hosts, have been reported as plastic degraders. The interaction between microbial species and invertebrate hosts often results in a profitable functional interplay, as for the biodegradation of plastics by insect-microbiota synergistic action. Among promising insects, Hermetia illucens larvae have been shown to effectively degrade two plastic polymers (i.e., polyethylene and polystyrene) thanks to bacterial communities inhabiting their midgut. Our research aimed to unveil the potential of H. illucens larvae and their gut microbiota in the biodegradation of polyethylene terephthalate (PET), commonly used in the manufacturing of products such as water bottles, food packaging, and textiles. Efforts were devoted to i) monitoring the growth and development of H. illucens on PET, ii) studying larval physiological responses to oxidative stress and damage triggered by PET exposure, and iii) characterizing shifts in microbial community composition in different larval gut regions caused by PET ingestion. Our results demonstrate that H. illucens larvae can survive up to 60 days on PET-based diets, although with substantial growth and development impairment. We detected a remodeling of the larval fat body and the activation of an effective response to cope with oxidative stress induced by PET ingestion. Moreover, we observed shifts in microbial communities in the larval gut regions after the ingestion of PET. Results herein presented demonstrate that H. illucens larvae are able to resist to consistent PET exposure and give first evidence of the possibility of using this insect as a bioincubator for the isolation of PET-degrading microorganisms or enzymes.