Integrating DFT-guided design and green natural deep eutectic solvent chemistry for efficient keratin dissolution and recovery from wool waste

Keratin, a structurally resilient protein abundant in wool, remains underutilized due to challenges in its efficient extraction and regeneration. In this study, density functional theory (DFT) calculations were employed to investigate four molar ratios of lactic acid (LA) to sodium acetate (NaOAc) in a natural deep eutectic solvent (NADES) system. Computational descriptors, including interaction energies, topological, and electron localization analyses, indicated that the 2:1 LA:NaOAc ratio provides the most favorable environment for disrupting keratin disulfide bonds through cooperative hydrogen and chalcogen bonding. Guided by these predictions, experimental extractions conducted at 110 °C for 4 h with a fiber-to-liquid ratio of 2.5 % yielded the highest keratin recovery (21.83 %), significantly surpassing other formulations. Spectroscopic (FTIR, EDX), thermal (TGA/DSC), morphological (SEM), and crystallographic (XRD) analyses confirmed that the regenerated keratin retained its structural integrity and characteristic features. Furthermore, the NADES exhibited excellent recyclability over five extraction cycles with only a 15 % decrease in performance. This integrated computational-experimental approach establishes a cost-effective and environmentally benign strategy for keratin valorization, highlighting the potential of NADES-based systems for sustainable biopolymer processing.