Extraction of keratin from sheep wool fibres using aqueous ionic liquids assisted probe sonication technology

Wool derived keratin is a potential biopolymer that can play a vital role as a cheap, sustainable, renewable source of material for designing various speciality products in the field of biomedicine. Unlike conventional methods for keratin extraction, the use of eco-friendly, a recyclable solvent like ionic liquids opens a new perspective for the processing of natural raw materials from livestock industries. In this research work, we develop a technique for rapid dissolution of keratin in ionic liquid assisted by probe sonication without any heating from an external source. The whole process of keratin extraction was optimized concerning the type of ionic liquid, sonication time, initial loading of the sample, and acoustic power of probe sonicator. The properties of regenerated keratin were studied further by using various analytical techniques such as Scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) analysis, thermogravimetric analysis (TGA), Nuclear magnetic resonance (NMR) spectroscopic analysis, Sodium dodecyl sulphate -polyacrylamide gel electrophoresis (SDS-PAGE). FTIR analysis showed the protein secondary structure and TGA analysis further revealed improved thermal properties of regenerated keratin when compared to raw untreated wool. The presence of intermediate filament derived low sulphur keratin along with some fraction of matrix protein in regenerated keratin was confirmed by SDS – PAGE analysis. Thus, further efforts are required to implement this technique at larger industrial scale to make this whole process of keratin extraction economical, quick, and environmentally friendly.