Insects have an external skeleton composed mainly of chitin. Chitin is a long-chain polysaccharide with functional groups that make it a valuable biopolymer for a broad range of applications. Chitin is an almost inexhaustible resource, as it is constantly produced in huge quantities throughout nature. At present, chitin is mainly produced from fish industry waste. The extraction of insect chitin has not yet been considered. Researchers from the Fraunhofer Institute for Interfacial Engineering and Biotechnology (IGB) and six cooperation partners are working on developing a biotechnological method for making insect chitin usable for coating textiles.
Chitin is a biopolymer composed of long acetylglucosamine chains that is produced by many organisms. For example, it is a characteristic component of the external skeleton of insects, crustaceans and the cell walls of fungi. This makes chitin one of the most abundant polymers on earth. Several billion tons of chitin are produced naturally every year. Theoretically, chitin is an almost inexhaustible raw material. However, it is still largely seen as waste, rather than a raw material. While attempts to process shrimp shells for use as raw materials in the polymer industry have been quite successful, with insect chitin, the situation is different as methods for sustainably refining the polymer are currently unavailable. Neither has any economically viable chitin resource been available until recently.
Dr.-Ing. Susanne Zibek, Dr.-Ing. Thomas Hahn and their team of researchers from the Fraunhofer Institute for Interfacial Engineering and Biotechnology (IGB) in Stuttgart are working with six national and international partner institutions on a project called ChitoTex. The project began in 2015 and is coordinated by Dr. Zibek. The researchers are looking into ways of refining insect chitin and using it as functional coating for yarn and fabrics in the textile industry. They use chitin produced by Hermetia illucens, the black soldier fly, which is bred by a Dutch company called Protix. The company breeds the insects on GMP+-certified plant residues from the food and feed industry to produce high-quality protein for animal feed. The same high-quality protein is also being considered for use as a component of human food,” says Hahn. “As soon as we can be sure that no contaminants or microorganisms are present in the final product, this type of protein food will also be suitable as human food.”
At the start of the project, the chemists from Stuttgart received a variety of chitin samples from the Dutch insect company in which they determined the quantity of chitin. Samples with the largest quantities were then selected for further processing. “In an earlier project, the researchers had isolated two microorganisms with chitinolytic capacities,” said Hahn. “In addition to coordinating the ChitoTex project, our group is also focused on developing methods for refining insect chitin, as well as enzymatically degrading chitosan and chemically modifying it. We are working on this with our project partners. We are also carrying out chitin analyses.” The IGB researchers also plan to create decentralised chitin resources where chitin is needed, especially in view of its future use in human food. “Two kilogrammes of insects can be produced from one kilogramme of food waste. This is much more sustainable than beef or pork production,” says the scientist. “Insect chitin will be a by-product.“
The project is now halfway through, and a large part of it has already been successfully completed: the researchers’ Norwegian project partner, the Norwegian University of Life Sciences, has identified several chitinolytic genes, which are now being expressed by the group’s Austrian project partner, an enzyme specialist called EUCODIS Bioscience GmbH. “At the IGB, we will later focus on processing insect chitin into chitosan using a special enzyme cocktail,” says Hahn. Chitosan is a versatile raw material for producing many different biopolymers. At present, the IGB researchers and their partners from the textile industry, Reutlingen-based Dr. Petry GmbH and Lauchringen-based Lauffenmühle GmbH & Co KG, are studying ways of functionalising chitosan and using it for coating textiles. The researchers hope that natural chitosan will contribute to greater sustainability in the textile industry, which is currently very chemical-based.
“Our aim is to create better and more environmentally friendly products for the textile industry,” says the chemist. Insect chitin-based products can be used for textile sizing1 which, amongst other things, changes the wear resistance of textiles. Coating textiles with chitosan protects them and prevents damage.” In addition, the researchers want to establish a method for functionalising chitosan amine groups; the amine groups could then be used as an anchor for other molecules, such as those that increase the wash resistance of textiles, thus introducing another functionality. A first type of coating with promising characteristics has already been produced, but the researchers are not yet happy with the results. Further optimisation work is therefore needed. Once the desired properties have been achieved, the researchers will increase the production scale and transfer the positive characteristics of chitosan such as its antimicrobial effect to textiles. In contrast to other substances such as silver threads, which are incorporated into functional socks, chitosan is non-toxic and biodegradable.
Dr. Hahn is convinced that in future, there will be a wide range of products involving the use of insect chitin, in both the textile and other industries. Hahn’s project partners from the textile industry are extremely open-minded as far as the use of biotechnologically produced substances is concerned. However, at present 90 percent of all substances used are still of petrochemical origin. Although cellulose fibres are already widely used in the textile industry, they are coated with substances that are not sustainably produced.
1 Sizing: In the textile industry, sizing liquor is applied to yarn in order to make the threads smoother and more resistant to mechanical stress, thus making it less liable to break.