Structural and functional assessment of keratin extracted from chicken feathers using microwave-assisted l-cysteine method

Abstract

Extracting and applying waste feather keratin are important environmental challenges. This study utilized microwave-assisted l-cysteine treatment on chicken feathers, pH adjustments varied reducing capacity of l-cysteine, while modulated microwave power explored synergistic extraction effects on properties of keratin. The highest yield of regenerated keratin was achieved at an l-cysteine concentration of 15 g/L, pH 12, and a microwave power of 400 W. Micromorphological and particle size results revealed that the keratin particle size increased with pH dependency, the highest proportion of particle size values in keratin increasing from 164 nm in L1 (extracted at pH 11) to 220 nm in L5 (extracted at pH 13). Increasing the intensity of both treatments led to a transition of the secondary structure of regenerated keratin from α-helix to β-sheet, but the increasing reducibility of the system resulted in a decrease in the content of tryptophan residues in keratin, whereas the increase in microwave power led to the masking of some fluorescent chromophores within the keratin. The regenerated keratin demonstrated low crystallinity, and it may have undergone refolding and aggregation under microwave-assisted highly reducing extraction conditions. The foaming properties indicated that the highly reducing extraction system significantly decreased foam stability from 95.4% for L1 to 19.8% for L5 (p < 0.05) and improved foaming ability to keratin. Considering the widespread applications of keratin, this study provides a comprehensive characterization of regenerated keratin under different extraction conditions, aiming to offer experimental materials and extraction conditions tailored to specific requirements in the field of biomaterials.