August 14, 2022

Fibroin is an insoluble protein produced by spiders, the larvae of the Bombyx mori (silkworm), organisms belonging to other moth genera (Antheraea, Cricula, Samia, Gonometa, etc.), and also many other insects. The two main components of silk are a protein called sericin and fibroin, here fibroin is the central substance, surrounded by the sticky sericin. Fibroin proteins consist of layers of beta sheets in opposite directions, and the amino acid (Gly-Ser-Gly-Ala-Gly-Ala) repeats in its primary structure. The high glycine (and some alanine) content allows the sheets to be compacted into a small space, which gives the silk its rigid structure and tensile strength. Due to the combination of stiffness and stretchability, it is used in countless fields, including pharmaceuticals and the textile industry. Three types of fibroin structures are known, and they are called silk-I, -II and -III. Silk-I is the natural form of fibroin secreted by the silk glands of Bombyx mori. Silk-II refers to the arrangement of the fibroin molecules in spun silk, which is a very strong material and is used in a variety of ways in commerce. Silk-III is a newly discovered structure of fibroin. Silk-III is mainly formed at the surface of fibroin solutions (ie at the air-water or water-oil interface, etc.).


Numerous species of Amycolatopsis and Saccharothrix bacteria are able to break down polylactic acid and fibroin in silk into monomers.


This article is based in part or on a translation of this version of the English Wikipedia article Fibroin. The editors of the original article are listed in its page history. This indication only indicates the origin of the wording, it does not serve as a reference to the source of the information in the article.