Insect holobionts as a valuable tool for the valorisation of waste biomass rich in recalcitrant polymers

Abstract Some insect species represent sustainable tools for the bioconversion of organic waste into valuable products, supporting the development of circular economy supply chains. However, their bioconversion efficiency is significantly reduced in the presence of recalcitrant polymers, such as plastics and lignocellulose. Although conventional pretreatment methods — chemical or thermal — are useful for degrading these compounds, they are often expensive and environmentally harmful. In contrast, insect holobionts (i.e. the host and associated gut microbiota) reared on recalcitrant polymers may offer a nature-based alternative. Indeed, microbial strains and enzymes capable of breaking down these polymers can be isolated from their gut, and their activity can be improved through biotechnology and synthetic biology. In this setting, highly efficient bioconversion agents, such as black soldier fly larvae, and wood-decomposing insects like termites and their symbionts, represent a rich and underexplored resource for tackling persistent waste challenges through microbial biotechnologies.