Structural stability of two promising keratinases in human hair degrading ionic liquids: paving the way for more efficient and sustainable keratin extraction

Keratin derived from human hair has garnered significant attention for its biomedical applications. While ionic liquids (ILs) and keratinases independently facilitate hair hydrolysis, their synergistic use remains largely unexplored. Here, we computationally investigate the possibility of combining the use of ionic liquids and keratinases. We present here the structure of kerF and kerC, two keratinases identified from literature as promising candidates for human hair degradation, predicted using AlphaFold2. Subsequently, we performed molecular dynamics simulations to investigate the stability of these keratinases in water and six ionic liquids, chosen based on their recorded human hair degradation efficiency. The stability analysis was conducted using key metrics such as root mean square deviation (RMSD), root mean square fluctuation (RMSF), radius of gyration (Rg), solvent accessible surface area (SASA), and number of intra-protein hydrogen bonds. Computational data indicate that kerF exhibits stability in both water and two ionic liquids: 1-Allyl-3-methylimidazolium chloride [AMIM]Cl, and 1-butyl-3-methylimidazolium bromide [BMIM]Br. kerC remains stable in [AMIM]Cl. The results suggest the potential utility of these two keratinases in environmentally friendly keratin extraction processes from human hair waste. This study aims to identify suitable keratinases and advances the understanding of their stability in non-conventional ionic liquid solvent systems, supporting the development of sustainable, eco-friendly strategies for the extraction of valuable human hair keratin.