No abstract

Black soldier fly allows to efficiently convert residual biomasses into a valuable source of biomolecules, such as proteins, lipids and chitin. In this study, a new method for obtaining amorphous chitin from the black soldier fly larvae was developed with a further deacetylation step. Amorphous chitin was obtained by direct extraction using concentrated phosphoric acid. The purity of the resulting chitin was confirmed by physicochemical methods (elemental analysis, IR spectroscopy, measurement of primary amines, amino acid analysis). Crystalline chitin and high molecular weight chitosan were obtained by the standard procedure including demineralisation, deproteinisation and deacetylation steps. This method allows to extract chitosan, suitable for a wide range of applications.

Chitosan, obtained by deacetylation reaction of chitin, is a regular biopolymer with unique properties, including high biological and sorption activities. Melanin is considered as a natural photo and radio protector. Depending on the source and the isolation method, melanin possesses various physicochemical properties that can complement the radioprotective activity of chitosan and be used to solve important scientific and practical issues. Insects are relatively understudied natural sources of chitin-melanin complexes, whereas these components are linked by strong covalent bonds. This study developed a technology for the production of this natural conjugate, based on which its deacetylated derivative, the chitosan-melanin complex, was obtained, taking the black soldier fly as an example.

This study shows the research on the depolymerisation of insect and crab chitosans using novel enzymes. Enzyme preparations containing recombinant chitinase Chi 418 from Trichoderma harzianum, chitinase Chi 403, and chitosanase Chi 402 from Myceliophthora thermophila, all belonging to the family GH18 of glycosyl hydrolases, were used to depolymerise a biopolymer, resulting in a range of chitosans with average molecular weights (Mw) of 6–21 kDa. The depolymerised chitosans obtained from crustaceans and insects were studied, and their antibacterial and antifungal properties were evaluated. The results proved the significance of the chitosan’s origin, showing the potential of Hermetia illucens as a new source of low molecular weight chitosan with an improved biological activity.