E. Nuutinen: Keratin building blocks from feathers for material applications

Abstract:

Feathers, a byproduct of the poultry industry, are a rich source of keratin. Thus, the valourization of feathers is highly relevant, considering the aspects of resource sufficiency and the circular economy. This doctoral thesis aimed to convert feathers into keratin building blocks and evaluate their utilization in material applications. Keratin as a structural protein has interesting properties, considering applications in the medical, cosmetics, electronics, agriculture, textile and composite industries. To produce molecular keratin, feathers were dissolved in an aqueous deep eutectic solvent (DES). It was found that the DES used was able to disturb the interactions within the feather keratin, cleave the disulfide bonds, alter the conformation and partially break down the polypeptide backbone, and that the molecular weight of the keratin played an important role in its solubility. Film structures were prepared from molecular keratin to study the physical properties and reactivity of keratin. The conformation and molecular weight of keratin, as well as the addition of plasticizers and cross-linkers, had determinant roles in the mechanical properties and water sensitivity of the films. To compare the used DES process to a mechanical treatment, a simpler alkaline pre-treatment combined with milling was carried out to produce fibrous keratin. A comparison of films made of molecular and fibrous keratin showed that fibrous keratin is suitable in applications such as composites, in which transparency, good barrier properties or reactivity are not required, while molecular keratin is suitable in various applications. To evaluate the possibility to combine keratin with other bio-based materials, the adsorption of keratin peptides obtained from the used DES process on cellulose and lignin substrates was studied. The interactions between cellulose and keratin peptides were found to be weak, while on lignin substrates, keratin peptides had high adsorption. The structural properties of keratin—including the amino acid content, molecular weight, and random coil conformation together with the negative net charge of lignin surfaces—were demonstrated to be the determinanting factors in for the adsorption behaviour. In particular, the combination of colloidal lignin particles and keratin is interesting, as the spherical morphology of the nanoparticles is beneficial in many practical applications. Overall, the thesis furthers our understanding of how the choice of the processing method affects the structural and physical properties of the feather keratin as well as its interactions with lignocellulosics. These are important for the utilization of keratin in macro- and nanoscale material applications.

Follow the remote defence: TBA

Opponent: Dr. Koon-Yang Lee, Imperial College London, United Kingdom

Supervisor: Professor Monika Österberg,  Aalto University, School of Chemical Engineering, Department of Bioproducts and Biosystems

Link to electronic thesis: Keratin building blocks from feathers for material applications