Reassembly mechanism of keratin structures for the valorization of keratinous wastes

Reassembly mechanism of unique keratin structures has been elucidated in this study. Recently, there has been a growing focus on keratin attributed to its remarkable biocompatibility, biodegradability, renewability, and abundant availability. However, the advancement of high-quality keratin products has been constrained by their insufficient mechanical properties. While extensive research has been devoted to the extraction of high molecular weight keratin, relatively limited attention has been given to the reassembly mechanisms of unique keratin structures. In this study, we have demonstrated that unfolded keratin backbones can be readily refolded into ordered structures, provided that no branching of keratin chains occurs. However, the hydrolysis of SS bonds induces branching in keratin polypeptides and sulfur loss, which hinders the efficient reassembly of ordered structures and sulfide crosslinkages, consequently results in suboptimal mechanical properties. Conversely, regenerated keratin products with minimal hydrolysis of SS bonds exhibit crystallinity and sulfide crosslinking comparable to that of their natural counterparts, yielding unexpectedly favorable mechanical properties. Clarifying the reassembly mechanism of unique keratin structures is crucial for the valorization of waste keratin materials and the production of keratin products with high-quality.