A comprehensive comparative study of ultrasound-alkaline and thermal-alkaline hydrolysis of duck feather
Nidal Del Valle Raydan, Antoine Loquet, Birgit Habenstein, Brice Kauffmann, Bertrand Charrier, Grégory Châtel, Eduardo Robles
Abstract
Feathers, as a byproduct of the poultry industry, present a significant source of keratinous waste. Conventional methods have been widely used to extract keratin from feathers; however, they are associated with limitations such as high operational costs and environmental concerns. It is, therefore, crucial to develop cost-effective and time-efficient methods for extracting keratin on a large scale. In recent years, ultrasound-assisted alkaline hydrolysis has emerged as a promising and sustainable approach for efficient keratin recovery. This study compares the hydrolysis time, yield, and chemical properties of keratin extracted from feathers using ultrasound-assisted alkaline hydrolysis and thermal alkaline hydrolysis (hot plate method). The influence of factors such as particle size, alkali concentration, liquid-to-solid ratio, reactor geometry, temperature of keratin colloid upon precipitation, precipitation pH, and precipitating acid was investigated. Favorable conditions for ultrasound-assisted alkaline hydrolysis were found to be 3% NaOH, a 10:100 (w/v) solid-to-liquid ratio, using a cylindrical vessel, and an ultrasonic energy density of 360 kJ/L, with pH adjustment to 4.5 using citric acid after cooling to room temperature. This method outperformed the thermal approach, yielding 70% keratin in 25 min, compared to 23% in 90 min using a hot plate, due to the exothermic effect of cavitation. The results provide valuable insights into the potential of ultrasound-assisted alkaline hydrolysis as an eco-friendly and cost-effective approach to address the management of keratinous waste and enhance the overall recovery of keratin.