Hermetia illucens larvae as microbial bioincubator for the development of innovative strategies for plastic biodegradation

Plastic pollution represents a global concern, dramatically impacting ecosystems and human health, as artificial plastic polymers are persistent and inaccessible to most natural enzymes due to their physicochemical characteristics. However, bacterial and fungal species isolated from diverse sources, such as marine ecosystems, soil, and plastic landfills, have been reported as plastic degraders, with significant research efforts dedicated to identifying and engineering enzymes involved in the process to find novel and sustainable solutions for plastic degradation. Moreover, recent years have seen a significant increase in studies demonstrating the ability of insects and their gut microbiota to degrade these recalcitrant polymers, and among the most promising species there is the dipteran Hermetia illucens. Our recent research aimed to develop protocols for the rearing of H. illucens larvae on plastics-based substrates to select for plastics-degrading microorganisms, focusing on i) monitoring the growth and development of H. illucens on plastics-based diets, ii) studying larval physiological adaptation to plastics exposure, and iii) characterizing shifts in microbial community composition associated with the presence of the polymers in different larval gut regions and mining larval gut microbiome for plastic degrading functions. The results obtained so far demonstrated that the larvae are able to tolerate the rearing on different plastic polymers, surviving up to 60 days in plastic-based diets, although with a significant impairment of the growth and development. We observed the remodeling of the larval fat body and the activation of effective responses to cope with oxidative stress induced by plastic ingestion. Moreover, we detected a shift in the microbial communities in different larval gut regions, with an increase in the relative abundance of taxa with plastic-degrading properties. These data represent a solid foundation for using H. illucens larvae as a valuable bioincubator for culturable and unculturable microorganisms carrying plastic-degrading enzymes that can be identified and optimized through engineering and synthetic biology approaches.