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The processing of crustaceans from the fishing industry, the production of insect protein, and mushroom cultivation generate large quantities of chitin-containing waste. The Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB has established a process chain for chitin processing to create added value from these waste streams. These technologies enable the production of high-purity chitosan, which can be used, among other things, for sustainable coatings. Transparent films made from chitosan are suitable for use as biodegradable single-use packaging and could replace petroleum-based plastics.
The biopolymer chitin is primarily produced as a structural material by crustaceans, insects, and fungi and is – after plant-based cellulose – the second most abundant biopolymer on Earth. Due to its nitrogen content, chitin is already used in agriculture as a fertilizer and soil conditioner or for the production of chitosan. However, commercial use has so far been limited mainly to chitin, which is extracted from crab shells. Yet, the food industry and biotechnology sectors worldwide are generating hundreds of thousands of additional tons of chitin-containing residues: insect exoskeletons from insect protein production, mycelium residues from fungal fermentation, and trimmings from mushroom cultivation.
Researchers at the Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB have now succeeded in utilizing insect exoskeletons as well as mycelium-containing residues from fungal fermentation as sources of chitin for producing chitosan. To this end, the institute has established a process chain for chitin processing in which residual and waste streams are treated according to the principles of a biorefinery and converted into valuable materials.
Gentle extraction of chitin from various sources
The composition of chitin-containing residues varies from organism to organism. Crab shells and insect chitin, for example, must be freed from calcium deposits and proteins, while chitin in fungal mycelium is often bound to glucans. “We have adapted our chitin extraction processes to the various waste materials and tailored the necessary separation and processing steps to the respective chemical composition,” explains Dr. Thomas Hahn, who has been researching chitin processing at Fraunhofer IGB for many years. This also involved developing or refining analytical methods to assess the success of the processing. Only by knowing the exact chemical composition of the chitin-containing biomass can the valuable raw material be processed in a tailored manner. Using newly established analytical methods, the researcher monitors the chitin content of the intermediate products after each individual purification step.
Sustainable and economical at the same time
To preserve the chemical and physical properties of chitin, it should be separated from the remaining biomass as gently as possible. Hahn therefore prefers to use aqueous media or relies on enzymes to selectively remove impurities. To ensure that the subsequent industrial implementation is also economically viable, the chemist is already evaluating and optimizing the individual process steps at the laboratory scale with a view to upscaling. “If, for example, solvents, reagents, or wash water can be reduced or recycled, this has a positive effect on the overall cost of the process,” Hahn explains.
Optimized conversion of chitin to chitosan
Chitosan, which is soluble in slightly acidic solutions and therefore highly versatile, is produced by deacetylation of chitin. However, the production of chitosan from chitin is not trivial and requires a keen sense of chemistry and experience. Typically, the process takes place at high temperatures and under harsh chemical conditions. “Over the course of our many years of research, we have been able to moderate the reaction conditions, further optimize them, and increase the yield,” says Hahn. Through appropriate purification steps, the chemist achieves chitosan with a purity of more than 90 percent – from crab shells as well as from fungal mycelium and insect exoskeletons.
The subsequent analysis of the molecular weight, degree of deacetylation, and purity of the respective chitosan product already provides initial insights into possible applications. In a specially developed solvent-casting plate test, which examines film formation and swelling capacity, Hahn also identifies any compounds incompatible with chitosan as well as suitable cross-linking agents.
Chitosan: a versatile biopolymer that can replace petroleum-based polymers
Chitosan is extremely versatile: it has antibacterial and odor-inhibiting properties, adheres well, regulates adhesion and viscosity, can form films – and is completely biodegradable. Due to its antimicrobial and hemostatic properties and excellent biocompatibility, chitosan is used in wound dressings; the cosmetics industry is already taking advantage of its ability to retain moisture – in the form of moisturizing and skin-care components in creams and lotions.
Since the biopolymer provides binding sites for additional functionalities or molecules, Hahn has also modified it in various ways through internal collaboration at the institute. Additionally, it can serve as a matrix for a fluorine-free hydrophobic finish of textiles or as a bio-based flocculant for treating complex wastewater.
The biopolymer’s ability to form films makes it ideal for coatings and films to replace petroleum-based polymers. Hahn has produced transparent films after adding bio-based crosslinkers. “Due to their balanced elasticity and transparency, chitosan films are ideally suited as sustainable, bio-based, and biodegradable single-use packaging, e.g., in the food industry,” explains Hahn. Another advantage: By utilizing locally available resources on an industrial scale, fossil raw materials can be replaced and dependencies on international supply chains reduced.
CHITIN [C8H13NO5] _shelter: textile design prototypes made from spun chitosan fibers
Inspired by the natural origin and properties of the material, the design team at SurrealLabor explored chitosan as a raw material for textile applications. In the CHITIN [C8H13NO5] _shelter project, funded by the Fraunhofer Network “Science, Art, and Design” and with scientific support from Thomas Hahn, they spun chitosan fibers on a laboratory setup built specifically for this purpose using extrusion and wet-spinning processes and processed them into a textile fabric as design prototypes. By establishing, refining, and optimizing chitosan spinning production, the team aims to tap into a new, bio-based resource for the textile industry and contribute to a vision of tomorrow’s circular economy.
Dr. Thomas Hahn thomas.hahn@igb.fraunhofer.de
https://www.igb.fraunhofer.de/chitin-biorefinery
https://www.igb.fraunhofer.de/en/press-media/press-releases/2026/bio-based-films... Press release on the Fraunhofer IGB website, featuring additional images of textile design prototypes
To produce high-purity chitosan from insect exoskeletons, chitin is isolated, purified, and converte ...
Copyright: Fraunhofer IGB
Chitosan films are well-suited for packaging applications due to their balanced elasticity and trans ...
Copyright: Fraunhofer IGB
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Biologie, Chemie, Kunst / Design, Umwelt / Ökologie, Werkstoffwissenschaften
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