Bioinspired Processing of Keratin into Upcycled Fibers through pH-Induced Coacervation

Abstract

Keratin is an important byproduct of the animal industry, but almost all of it ends up in landfills due to a lack of efficient recycling methods. To make better use of keratin-based natural resources, the current extraction and processing strategies need to be improved or replaced by more sustainable and cost-effective processes. Here, we developed a simple and environmentally benign method to process extracted keratin, using HCl to induce the formation of a coacervate, a separate aqueous phase with a very high protein concentration. Remarkably, this pH-induced coacervation did not result in the denaturation of keratin, and we could even observe an increase in the amount of ordered secondary structures. The low-pH coacervates could be extruded and wet-spun into high-performance keratin fibers, without requiring heating or any organic solvents. The secondary structure of keratin was largely conserved in these regenerated fibers, which exhibited excellent mechanical performance. The process developed in this study represents a simple and environmentally friendly strategy to upcycle waste keratin into high-performance materials.

Effect of Dynamically Arrested Domains on the Phase Behavior, Linear Viscoelasticity and Microstructure of Hyaluronic Acid – Chitosan Complex Coacervates

“…Complex coacervation is a liquid–liquid phase separation formed through electrostatic interactions between oppositely charged polyelectrolytes and the subsequent release of the originally bound counterions and water molecules. , The resulting system consists of a polymer-rich viscoelastic phase, the complex coacervate, in thermodynamic equilibrium with a polymer-poor liquid phase. Complex coacervate materials have found use in a growing number of applications ranging from underwater glues, filtration membranes, fibers, structural materials, 3D printable inks, drug carriers, particulate emulsifiers, and many more. − …”

Upcycling of Keratin Wastes in Sustainable Textile Fiber Applications

“…As a result, regenerated wool fibers typically exhibit poor mechanical performance with a tensile stress of less than 100 MPa. 36,37 A recent investigation introduced an approach for revitalizing the disulfide linkage through the application of dithiothreitol (DTT) as a chain extension agent. This method yielded keratin fibers exhibiting a remarkable tensile strength of 180 MPa.…”

“…In addition, the secondary structure of keratin is stabilized by a range of noncovalent interactions, including electrostatic forces, hydrogen bonds, and hydrophobic forces and covalent disulfide bonds. , However, during the dissolution process, the fiber structure is deconstructed, and the protein constituents undergo denaturation, and it is challenging to rebuild this structure during the regeneration process. As a result, regenerated wool fibers typically exhibit poor mechanical performance with a tensile stress of less than 100 MPa. , A recent investigation introduced an approach for revitalizing the disulfide linkage through the application of dithiothreitol (DTT) as a chain extension agent. This method yielded keratin fibers exhibiting a remarkable tensile strength of 180 MPa.…”

Valorization of waste wool to keratin with a green solvent based on a deep eutectic mixture of choline chloride and lactic acid

“…The amide I peak at 1630 cm −1 and 1625 cm −1 arises from carbonyl stretching of the v(C=O) vibration in untreated wool and recovered keratins, respectively. The red-shift of the amide I peak to lower wavenumbers can be attributed to conformational changes in the keratin structure and increases in the proportions of beta sheets and disordered random coil structures [29,35]. The amide II peak arises from the in-plane N-H bending mode, dip(NH).…”