Dissolution and regeneration of wool keratin in the deep eutectic solvent of choline chloride-urea

Wool keratin is a kind of renewable protein which has great potential in environment-friendly materials. In this paper, the dissolution of wool fiber and the regeneration of wool keratin in the deep eutectic solvent (DES) of choline chloride-urea was detailed studied. The results showed that 35.1 mg wool completely dissolved in 1 g DES at 130 °C in 5 h. The polarizing microscope, scanning electron microscope (SEM) images along with the amino acid analysis suggested that the DES mainly dissolved the wool cortex layer. Compared with the raw wool, the regenerated wool keratin contained much more fragments of low molecular weight polypeptide chains from SDS-PAGE results. And the percentage of α-helix dramatically decreased, while the content of β-sheet and disordered structure increased. All the results indicated that the DES can be used as a kind of green solvent for the regeneration of wool keratin without losing the long peptide chains. The method also offered a possibility of large-scale for wasted wool reuse.