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.

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 (M_w) 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.

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.

The increase of organic wastes generated worldwide has become a global issue for the past years. Saprophagous insects including black soldier fly or Hermetia illucens have been a topic of interest among researchers due to their ability to recycle organic wastes. Once insect species mature, their biomass can be used to extract valuable biochemicals including chitin and melanin. In this study, the extraction schemes for obtaining chitin- and chitosan-melanin complexes from pupal exuviae and dead imagoes of Hermetia illucens were proposed, and their physicochemical properties were investigated. It was shown that black soldier fly can serve as a unique source of covalently bound chitosan-melanin complex with melanin content greater than 14%. In addition, the antioxidant activity of chitosan-melanin complex against DPPH activity was tested and compared to chitosan and melanin. It was revealed that chitosan-melanin complex possesses an enhanced antioxidant activity. These results suggested that black soldier fly is a promising source of chitosan-melanin complex with a high potential for cosmetic and biomedical applications.

Microorganisms are a significant cause of damage to cultural heritage, including paintings. Currently, the palette of antiseptics that are used in painting has narrowed considerably. This is due to the increased demands placed on such substances. It was shown that low molecular weight chitosan (LMWC) obtained from the king crab (Paralithodes camtschaticus) exhibits high activity against dominant fungi-destructors of paintings in the State Tretyakov Gallery. Nevertheless, the increasing market demand for chitosan has prompted the exploration of alternative sources. Insects, notably the bioconverter black soldier fly (Hermetia illucens), stand out as one of the most cultivated options. This study investigates the effectiveness of chitosan, isolated from H. illucens by a novel method developed by authors, in inhibiting fungi that damage tempera paintings. The activity of 33 and 39 kDa chitosans from H. illucens is comparable to the most active chitosans previously studied from P. camtschaticus. However, there are characteristic differences between these compounds, as shown by the results of FTIR spectroscopy, which may affect their consumer properties when used in paint materials. Our studies suggest that LMWC from H. illucens is a promising material that can expand the range of antiseptics used in painting. Graphical Abstract