Keratin recovery from sheep's wool: development and optimization of a membrane ultrafiltration process

Keratin recovery from wool industry waste is a key circular economy strategy for biomedical and cosmetic applications. However, industrial implementation is often hindered by purification complexities: removing extraction agents (chaotropic salts and surfactants) can compromise protein stability and solubility. This thesis optimizes a purification process based on hollow fiber ultrafiltration (UF-HF) using constant volume diafiltration (CVDF) to preserve keratin’s native water-soluble conformation. Trials were conducted at laboratory scale using MediSulfone (PSU) and PUREMA (PES) 15 kDa MWCO membranes. The study analyzed the impact of salt concentration (urea, SDS) and fluid dynamics parameters such as wall shear stress and lumen cross-flow velocity. Feed dilution was applied to mitigate concentration polarization and fouling. In parallel, a Piping and Flow Diagram (PFD) for a pilot unit was developed, integrating a feedback control loop to modulate the retentate valve based on Transmembrane Pressure (TMP). Results demonstrated high efficiency; gravimetric analysis confirmed a solid residue within the 1.1–1.3 wt. % range. ATR-FTIR spectroscopy verified the removal of SDS and salts while confirming protein structure preservation. Permeate flux modeling identified the prevalent fouling mechanisms, providing the basis for an industrial scale-up that confirms the technical feasibility of high-purity soluble keratin production.