Extraction, Processing and Applications of Wool Keratin

Keratins are proteins characterised by a high sulphur amount and by the presence of strong disulphide bonds which make keratins water insoluble and resistant to different chemical agents. Keratins with molecular weight ranging from less than 10 to 60 kDa are obtained by cleavage of the cystine bonds with reducing or oxidising agents or by sulphitolysis. Keratin oligopeptides can be obtained by cleavage of peptide bonds using strong acids or strong bases. Recently, green hydrolysis with superheated water and steam-explosion has been proposed with the aim of avoiding the use of harmful agents. Proteins extracted from wool can be processed alone, or in blend with other polymers, with crosslinking agents, or in the presence of additives (e.g. plasticisers). Keratins are biocompatible, biodegradable, hygroscopic, adsorb heavy metal ions, formaldehyde and other volatile organic compounds. So, keratin can be used in different fields in the form of films, sponges, nanofibres, microcapsules, hydrogels and powders especially for biomedical applications and filtration. In this review details on the extraction and processing of keratins from wool are reported, with some example of utilization for different practical applications.