An innovative, highly efficient and sustainable approach to wool keratin regeneration using reductive deep eutectic solvent

Purpose Protein fibers, such as wool, silk and rabbit hair, are commonly used in the textile industry, but millions of tons of them are discarded, resulting in environmental pollution and resource waste. Therefore, it is significant to explore an eco-friendly and highly efficient method for regenerating protein. Design/methodology/approach Cysteine is a natural and the only reductive amino acid that makes up natural protein; thus, in this study, a novel and eco-friendly choline/cysteine deep eutectic solvent was synthesized and introduced for the first time in protein regeneration. Findings The results showed that it can dissolve keratin faster with a higher solubility than other traditional methods. Based on Scanning Electron Microscope (SEM) and amino acid analysis, the cortex layer was split and dissolved earlier than the scale layer, accompanied by disulfide bonds partly broken by the Raman result. The next analyses revealed that regenerated keratin retained its high macromolecular chain and main secondary structure of natural wool. Moreover, the solvent could be recycled more than 10 times. The sustainability evaluation results show it is a green, highly efficient and low-cost approach for regenerating keratin with intact macromolecular chain structure. Originality/value This study has broadened the scope of clean application of Deep Eutectic Solvent (DES) in protein regeneration and contributes to interaction studies between DES and proteins.