“The scavenger insect Hermetia illucens: an innovative and alternative source of chitin and chitosan”

Chitin and chitosan are two biopolymers of great interest, thanks to their versatility and potential use in various application fields. Chitin is the most abundant biopolymer on Earth, second only to cellulose; it is a structural component of the exoskeleton of arthropods and of the cell wall of fungi. However, processing chitin is complicated because it is not soluble in water and in common organic solvents. For this reason, chitin is typically converted into its more soluble derivative, chitosan, through a deacetylation process that can be either homogeneous or heterogeneous. Currently, large-scale chitin extraction is industrially carried out using fishery by-products, especially crustacean shells. However, this commercial source is no longer considered highly sustainable and renewable, as crustaceans are subject to seasonal and geographical limits. Therefore, the increasing market demand for these two biopolymers has driven science to search for alternative, more sustainable, renewable, and readily available sources. In this perspective, insects, thanks to their abundance and biodiversity, represent a valid solution to this problem. Among the insects, the bioconverter Hermetia illucens is of great interest. This fly feeds on agri-food byproducts, converting them into larval biomass, rich in numerous molecules of high biological value, including chitin. The breeding of H. illucens is crucial, for instance, for the production of feed as an alternative to soy and fishmeal. Moreover, the farms produce a vast amount of waste products, like pupal exuviae, released from molting processes and dead adults, which are rich in chitin. They are thus recovered within a fully circular, zero-waste economy process. In this way, the extraction of chitin and the production of chitosan become entirely and highly sustainable procedures. The aim of this work was to study different biomasses from H. illucens breeding, such as larvae, pupal exuviae, and dead adults, as alternative sources of chitin and chitosan. Chitin was extracted from the three different H. illucens sources with characteristics and purity similar to the commercially available crustaceanderived chitin. The highest yield (23%) was obtained from pupal exuviae. Extraction methods proved to be efficient in purifying the raw insect samples. Chitosan was produced through heterogeneous and homogeneous deacetylation, revealing unique chemical-physical properties. To validate the biopolymer use in cosmetic, biomedical and pharmaceutical fields, in this thesis work some fundamental properties of H. illucens chitosan have been tested, such as anti-inflammatory, antifungal and antimicrobial activities. The investigation yielded great results: chitosan from H. illucens had similar or, in some cases, better effects 7 than commercial chitosan. Chitosan produced from larvae, pupal exuviae, and dead adults showed excellent anti-inflammatory, antifungal and antimicrobial activity, both direct and not direct. Indeed, indirect antimicrobial activity tested on immortalized human keratinocytes treated with lipopolysaccharide yielded optimal results. The anti-inflammatory activity was found also particularly intense, with significant effects, sometimes even better than those obtained from crustaceans chitosan, the control. Revealing and identifying these biological properties of chitosan from H. illucens paves the way for its applications, especially in biomedical, pharmaceutical and personal care fields. As a result, in this study, the biopolymer has been preliminarily employed for the production of chitosan nanoparticles for drug delivery. These systems were produced from all the three biomasses of H. illucens. The results obtained from dynamic light scattering and from the scanning electron microscope analysis demonstrated the formation of nanosystems with low diameter dimensions and smooth and regular morphology, suitable for future use in encapsulating bioactive molecules. Hence, this work highlighted the potential of H. illucens as a source of chitin and chitosan, for applications in the biomedical and pharmaceutical fields. The use of insect-chitosan, therefore, can contribute to improve human health both directly, due to its biological properties, and also indirectly, because it improves the quality of food commonly consumed by humans. Therefore, from this thesis work, the validation of the use of chitosan from H. illucens, as an alternative to the crustacean-derived biopolymer, emerges clearly, as it can be used effectively in areas directly related to human health and to improving human life. Chemical-physical and biological properties of chitosan from H. illucens, for all these reasons, are also important with regard to another sector, directly related to humans and their well-being, which is the agri-food sector. Insect-chitosan has also been studied in preventing the spoilage of fresh foods mostly consumed among the population, such as tomatoes, strawberries, peaches and grapes. The biopolymer has also proven to be particularly effective in improving the nutraceutical properties of processed fruits, such as phenol and flavonoid content. Indeed, these are known for their strong antioxidant properties, as they prevent damage caused by free radicals in the body, leading to premature ageing and various chronic diseases.