Upcycling Byproducts from Insect (Fly Larvae and Mealworm) Farming into Chitin Nanofibers and Films

Nowadays, environmental concerns make us rethink the way that we live and eat. In this regard, alternative protein sources are emerging; among them, insects are some of the most promising alternatives. Insect farming is still an infant industry, and to improve its profitability and environmental footprint, valorization of the byproducts will be a key step. Chitin as the main polysaccharide in the exoskeleton of insects has a great potential in this regard and can be processed into high value-added materials. In this study, we extracted and fibrillated chitin fibers from fly larvae (Hermetia illucens) and compared them with commercial chitin from shrimp shells. A mix of chitin and cellulose fibers was also extracted from mealworm farming waste. The purified chitinous fibers from different sources had similar chemical structures as shown by Fourier transform infrared and nuclear magnetic resonance spectroscopies. After mechanical fibrillation, the nanostructures of the different nanofibers were similar with heights between 9 and 11 nm. Chitin nanofibers (ChNFs) from fly larvae presented less nonfibrillated fiber bundles than the shrimp-derived analogue, pointing toward a lower recalcitrance of the fly larvae. ChNF suspensions underwent different film-forming protocols leading to films with tensile strengths of 83 +/- 7 and 71 +/- 4 MPa for ChNFs from shrimp and fly, respectively. While the effect of the chitin source on the mechanical properties of the films was demonstrated to be negligible, the presence of cellulose nanofibers closely mixed with ChNFs in the case of mealworm led to films twice as tough. Our results show for the first time the feasibility of producing ChNFs from insect industry byproducts with high potential for valorization and integral use of biomass.