Regenerated Hoof Keratin from 1‐Ethyl‐3‐Methylimidazolium Acetate and Insights into Disulfide‐Ionic Liquid Interactions from MD Simulation

Abstract

Regeneration of the hoof keratin from ionic liquids was never successful in the past because the ionic liquids were not strong enough. However, this biomaterial starts to play a central role for the preparation of biofilms in the future. In the present study, hoof keratin was regenerated for the first time from an ionic liquid by experiment and characterized by FTIR spectroscopy, Differential Scanning Calorimetry (DSC) and Scanning Electron Microscopy (SEM). As 1‐Ethyl‐3‐methylimidazolium acetate is strong enough to dissolve hooves, which have a lot of disulfide bonds, a Molecular Dynamics (MD) simulation was performed with this ionic liquid and diphenyl disulfide. The MD simulation reveals that not only the cation as postulated after experiments were carried out, but also the anion is very important for the dissolution process. This complete picture was and is not accessible via experiments and is therefore valuable for future investigations. The anion always interacts with the disulfide bond, whereas the cation prefers in some situations a strong H−O interaction with the anion. If the cations and the anions are separated from each other so that the cation can not interact with the anion, both interact with the disulfide bond. The high solvation power of this solvent is shown by the fact that the cation interacts from the left and right side and the anion from above and below the disulfide bond.

Valorization of chicken feathers using aqueous solutions of ionic liquids

“…The ILs selected comprise a combination of different cations and anions, taking into consideration the ILs that have been reported in the literature for the effective dissolution of different biopolymers from biomass. 29,31,[34][35][36][37] Nevertheless, to the best of our knowledge, the selected ILs have so far not been evaluated for chicken feather dissolution. The dissolution assays were carried out at 100 °C for 4 h in a solid : liquid (chicken feathers : solvent) ratio of 1 : 20 w/w in a carrousel (Carousel Tech, Radleys).…”

“…In 2005, 1-butyl-3-methylimidazolium chloride ([C 4 C 1 im]Cl) was used to dissolve wool and regenerate wool keratin for the first time, 25 and since then ILs have demonstrated excellent results with this type of biomass when properly selected. 20,23,29,30 Due to the wide variety of ILs and the complexity of keratin (which does not have regular repeating units), it is not easy to identify the best IL for keratin dissolution. To illustrate this, Liu et al 10 screened 621 ILs for the dissolution of three keratin models using COSMO-RS and validated it with experimental results.…”

“…Traditionally, when conventional dissolution (e.g., using urea and sodium metabisulfite) is carried out, either dialysis 28 or an adjustment of the isoelectric point using hydrochloric acid along with sodium sulfate 6,12 is necessary to recover keratin. When using ILs for biopolymer recovery, coagulant solvents, such as water 22 or ethanol, 29 can be used.…”

Characteristics of regenerated keratin and keratin-based film

“…The intense weight loss of the native kera tin sample in the temperature range of 206-276 °C (19.48 %) corresponds to the simulta neous processes of thermal denaturation of a-helices of intermediate filaments of native keratin and pyrolysis of the matrix [27]. This process is accompanied by a clear endothermic effect on the DTA curve and a deep extremum on the DTG curve.…”

Multiscale Conceptual Design of a Scalable and Sustainable Process to Dissolve and Regenerate Keratin from Chicken Feathers

“…Ionic liquids (ILs) have also been considered in the search of more specific solvents to dissolve the keratin contained in different raw materials. – They are excellent candidates because their properties can be tuned by selecting or modifying properly the constituent cations and anions . Remarkably, ILs can selectively break disulfide bonds, preserving the protein backbone.…”