Mining the Hermetia illucens larval gut microbiome to find novel plastic-degrading enzymes

Plastic pollution poses a major global challenge, driven by the persistence and widespread use of these synthetic polymers. Considerable scientific efforts have been directed toward developing innovative strategies for plastic waste valorisation, with enzymatic plastic biodegradation emerging as a promising and environmentally sustainable approach. Several plastic-degrading bacterial species have been isolated from disparate sources, such as marine ecosystems, soil, plastic landfills, and even and even the gut microbiota of invertebrates. In recent years, significant breakthroughs have been achieved in plastic biodegradation through the synergistic action of insects and their associated microbiota. Among promising insects, Hermetia illucens (Black Solder Fly, BSF) larvae displays the ability to grow on different plastics, such as polyethylene (PE), polystyrene (PS) and polyethylene terephthalate (PET). The intestinal microbiome of the larvae is significantly shaped by plastics ingestion and, at least for PE, it is involved in its biodegradation. Our research aims to: i) characterizing the shifts in the taxonomic composition of the intestinal microbial community caused by the ingestion of different plastics, and ii) reconstructing an in-silico functional profile of the gut community, focusing on enzymes that are putatively involved in plastics biodegradation. The results obtained provide a solid foundation for using H. illucens larvae as a bioincubator for both culturable and unculturable microorganisms carrying plastic-degrading enzymes which can subsequently be identified and optimized through protein engineering and synthetic biology approaches. In addition, the potential of the colonization of the intestinal microbiome with recombinant bacteria expressing such improved enzymes is discussed.