Ultrasound-Assisted alkaline hydrolysis of feather keratin using a cup horn sonoreactor

This study explores the potential of ultrasound-assisted alkaline hydrolysis, employing a cup horn sonoreactor, for the sustainable extraction of keratin from duck feather waste. Unprecedented in its approach, this research evaluates the system's efficacy in maintaining the structural integrity of cystine-a crucial amino acid-through controlled hydrolysis processes, or promoting disulfide bond rupture and regeneration upon precipitation. By using the unique advantages of the cup horn system, including homogeneous energy distribution and gentle processing, this investigation aims to overcome the limitations of hydrothermal treatments. The obtained keratins were analyzed using advanced spectroscopic, microscopic, and thermal analysis techniques (ATR-IR, Raman, SDS-PAGE, SEM, 13C CP-MAS NMR, XRD, and TGA). These analyses allowed the unveiling of the reaction pathways and structural changes in keratin under various temperatures in alkaline conditions. Lower temperatures (35 °C) favored the preservation of native disulfide linkages, while higher temperatures (75 °C) enhanced disulfide bond rupture and reformation. An intermediate temperature (55-65 °C) offered a balance between structural integrity and yield. This innovative method represents a significant advancement in feather waste valorization, providing a scalable and adaptable platform to tailor keratin properties such as yield, thermal stability, or disulfide bond regeneration, according to specific application needs.