Molecular design and experimental study of deep eutectic solvent extraction of keratin derived from feathers

Feather keratin has a complex structure, hard texture and must be treated to improve its bioavailability. In this paper, according to the designability of DES, some deep eutectic solvents (DESs) were prepared to degrade feathers and extract keratin. Calculations by quantum chemical methods showed that DESs were considered molecular scissors with the ability to break initial hydrogen bonds and form new bonds only when the Gibbs free energy change for the degradation process was ΔG < 0, i.e., hydrogen binding energy ΔE < -0.3038 kcal/mol. Then, the degradation mechanism was predicted to provide guidance for the molecular design of DES. Finally, experimental results showed that the same ratio of choline chloride-based DESs had higher catalytic performance, in which [ChCl][P][ZnCl₂] 1:5:2 was used with a high yield of keratin of 85.46 %. DES had a high catalytic performance after multiple recycling cycles and this method has no H₂S gas generation, which improves the atomic utilization.