Keratinases are exciting proteolytic enzymes that display the capability to degrade the insoluble protein keratin. These enzymes are produced by diverse microorganisms belonging to the Eucarya, Bacteria, and Archea domains. Keratinases display a great diversity in their biochemical and biophysical properties. Most keratinases are optimally active at neutral to alkaline pH and 40-60 degrees Celsius, but examples of microbial keratinolysis at alkalophilic and thermophilic conditions have been well documented. Several keratinases have been associated to the subtilisin family of serine-type proteases by analysis of their protein sequences. Studies with specific substrates and inhibitors indicated that keratinases are often serine or metalloproteases with preference for hydrophobic and aromatic residues at the P1 position. Keratinolytic enzymes have several current and potential applications in agroindustrial, pharmaceutical, and biomedical fields. Their use in biomass conversion into biofuels may address the increasing concern on energy conservation and recycling.
A novel feather-degrading microorganism was isolated from poultry waste, producing a high keratinolytic activity when cultured on broth containing native feather. Complete feather degradation was achieved during cultivation. The bacterium presents potential use for biotechnological processes involving keratin hydrolysis. Chryseobacterium sp. strain kr6 was identified based on morphological and biochemical tests and 16S rRNA sequencing. The bacterium presented optimum growth at pH 8.0 and 30 degrees C; under these conditions, maximum feather-degrading activity was also achieved. Maximum keratinase production was reached at 25 degrees C, while concentration of soluble protein was similar at both 25 and 30 degrees C. Reduction of disulfide bridges was also observed, increasing with cultivation time. The keratinase of strain kr6 was active on azokeratin and azocasein as substrates, and presented optimum pH and temperature of 7.5 and 55 degrees C, respectively. The keratinase activity was inhibited by 1,10-phenanthroline, EDTA, Hg(2+), and Cu(2+) and stimulated by Ca(2+).
The aim of the study was to characterize feather‐degrading bacteria isolated from poultry industry waste. A Vibrio sp. strain kr2 producing a high keratinolytic activity when cultured on native feather‐containing broth was isolated. The bacterium grew with an optimum at pH 6·0 and 30 °C, where maximum feather‐degrading activity was also observed. Keratinase production was similar at both 25 and 30 °C, while the maximum concentration of soluble protein was reached at 30 °C. Reduction of disulphide bridges was also observed, increasing with cultivation time. The keratinase of strain kr2 was active on azokeratin, azocasein, benzoyl‐arginine‐p‐nitroanilide and Ala‐Ala‐p‐nitroanilide as substrates. The amino acid composition of the feather hydrolysate was determined, presenting similarities with that reported for feather lysate, feather meal and raw feathers. A novel feather‐degrading bacterium was isolated and characterized, showing high keratinolytic activity. Complete feather degradation was achieved during cultivation. Strain kr2 shows potential for use for biotechnological processes involving keratin hydrolysis.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.