Keratin hydrolysate from chicken feather using alkaline-enzyme hydrolysis

Abstract

Background: Chicken feathers are a major byproduct of the poultry industry, containing 91% keratin protein. The protein’s
structure, with its hydrophobic interactions and disulfide bonds, makes it difficult to break down using conventional
methods. However, these structural properties make chicken feather keratin a valuable resource for product development.

Objectives: This study aims to develop and evaluate a combined alkaline-enzyme hydrolysis method for keratin extraction
from chicken feathers. The research examines molecular weight distribution and ionic characteristics of both soluble (SKAH) and precipitate (P-KAH) keratin fractions.

Methods: The alkaline-enzyme hydrolysis process used 0.5 M NaOH with 1% alcalase at 60°C for 22 hours. Subsequent
fractionation at pH 4.5 produced soluble (S-KAH) and precipitate (P-KAH) fractions. Characterization involved ultrafiltration
using 3 and 10 kDa membranes and ion-exchange chromatography.

Results: The combined alkaline-enzyme hydrolysis method yielding 87% total keratin. Analysis revealed two distinct
fractions: soluble keratin hydrolysate (S-KAH) constituted 72% of the yield, while precipitate keratin hydrolysate (P-KAH)
comprised 17%. Ultrafiltration analysis showed that S-KAH predominantly contained peptide fragments under 3 kDa
(58%), whereas P-KAH exhibited primarily larger fragments exceeding 10 kDa (81%). Ion-exchange chromatographic analysis
at pH 7.0 revealed that both S-KAH and P-KAH displayed anionic characteristics with neutral peptide components.

Conclusion: The alkaline-enzyme hydrolysis method demonstrated high efficiency in keratin extraction from chicken
feathers, yielding high extraction rates and distinct protein fractions characterized by specific molecular weights and ionic
characteristics. The results indicate potential for large-scale industrial application.