Nutritional improvement of feather protein by treatment with microbial keratinase

Chicken feather hydrolysate was produced by proteolysis with a keratinolytic bacterium. Feather hydrolysate was produced by using the whole culture on 60 g feathers/l (WCH), or alternatively, using only the culture supernatant of cultivation on 10 g feathers/l (CSH). The amino acid composition of the resulting hydrolysates was determined, indicating deficiency in methionine, lysine and histidine. CSH showed higher amounts of sulfur-containing amino acids than WCH. In vitro digestibility with pepsin plus pancreatin was evaluated. WCH had lower digestibility than soy protein, but higher than feather meal and milled raw feathers. CSH had similar digestibility than casein and soy protein. Predicted nutritional parameters for WCH, CSH and feather meal were calculated. WCH showed higher predicted values of protein efficiency ratio (PER) and biological value (BV) than CSH, which presented higher protein digestibility-corrected amino acid scoring (PDCAAS). These bacterial feather hydrolysates showed potential for utilization as ingredients in animal feed.