Sulfitolysis and Alkaline Extraction of Feather Keratin

Abstract The poultry industry generates millions of tons of feathers every year, creating environmental challenges but also offering opportunities for keratin recovery. This study optimized two cost-effective keratin extraction methods, alkaline and sulfitolysis. Factorial design analysis was utilized to assess the effects of process parameters on the feather dissolution rate. For alkaline extraction, NaOH concentration, temperature, and time were varied. Optimal conditions (0.5 M NaOH, 80 °C, 30 min) achieved a dissolution rate of 99.67 ± 0.09% and a keratin yield of 53.62 ± 1.62%. In the sulfitolysis method, parameters including sulfite type and concentration, urea concentration, SDS concentration, temperature, and solid-to-liquid ratio were analyzed. The highest dissolution rates were obtained with 0.5 M Na₂SO₃, 8 M urea, 0.25 g SDS/g feathers at 100 °C for 6 h and 1:15 solid-to-liquid ratio, yielding 98.30 ± 0.30% dissolution and a keratin yield of 64.48 ± 7.72%. Characterization indicated molecular weights of 10–20 kDa, preservation of secondary protein structures, and thermal stability comparable to feathers. XRD showed greater crystallinity in alkaline keratin, while SEM confirmed complete feather dissolution. Both methods provide low-cost, effective alternatives to alternative methods. However, differences in yield and material properties suggest sulfitolysis keratin is more suitable for thermally processed biopolymers, while alkaline keratin is better for cosmetic and food applications. Graphical Abstract