Biological activity of peptides isolated from feather keratin waste through microbial and enzymatic hydrolysis

Abstract

Background: A major portion of poultry feather waste is constituted by keratin, which is recalcitrant to degradation by common proteases. Feather waste contributes to a significant volume of biowaste load to the environment. Valorization of these wastes into various products has been attempted by many researchers. The present study aimed to produce peptides (molecular weight < 10 kDa) from feather waste by the action of keratinolytic bacteria or keratinase enzyme and to screen the peptides for pharmaceutical and therapeutic properties. The feathers were subjected to hydrolysis by using locally isolated keratinolytic microorganisms, namely Streptomyces tanashiensis-RCM-SSR-6, Bacillus sp. RCM-SSR-102, and purified keratinase enzyme KER-102.

Results: The feather keratin hydrolysate obtained by hydrolysis with different bacterial species/enzymes showed different protein profiles in SDS-PAGE. As indicated by Fourier Transform Infrared Spectroscopy (FTIR) analysis, a difference was observed in the composition of α-helix and β-sheet in the peptides produced by different microbial/enzymatic methods. The peptides were screened for antioxidant potential, antityrosinase property, and inhibitory activity against angiotensin-converting enzyme (ACE), lipoxygenase, and xanthine oxidase. The peptides showed promising results in all the assays, except peptide-102 that did not show ACE inhibitory activity. Interestingly, the crude peptide-6 (4.06 µg/mL) and peptide-102 (10.21 µg/mL) showed a lower EC₅₀ value than the standard Kojic acid (27.04 µg/mL) in antityrosinase assay.

Conclusions: Degradation of chicken feather waste with microbial or enzymatic method is an eco-friendly approach to yield diverse bioactive peptides. Hence, the present study established that feather keratin could be a potential source of many health-beneficial peptides.