Chryseobacterium aquifrigidense keratinase liberated essential and nonessential amino acids from chicken feather degradation

Thermoactive metallo-keratinase from Bacillus sp. NFH5: Characterization, structural elucidation, and potential application as detergent additive

“…The removal of metal ions by ion chelators stalled the activity of KerBAN, suggesting that inherent metal ion(s) are crucial for the catalytic integrity of the enzyme [ 69 ]. A similar inhibition pattern was observed among other bacterial keratinases [ 4 , 64 ]. All the metal ions tested did not enhance KerBAN activity, which shows that this metallo-keratinase does not require extra cofactors to attain optimal catalytic efficiency.…”

“…This property has been said to promote their application in industrial productions, like leather processing and detergent formulation [ 22 , 56 ]. The decrease in enzyme activity at neutral pH may be attributed to the orientation of catalytic cleft or side chains at this pH condition, affecting substrate binding and product formation [ 4 ]. Vieille and Zeikus [ 57 ] have defined enzymes that retain maximum activity at >80 °C as hyperthermophilic enzymes.…”

“…Keratin is a structural polypeptide with a high degree of insolubility occasioned by excess cross-linkages from hydrophobic interactions, hydrogen, and disulfide bonds [ 4 ]. Keratin-rich materials, such as avian feathers, generated in large amounts from poultry-processing farms often constitute serious environmental concerns due to their potential for litter, the generation of foul odors, and the ability to harbor pathogens [ 5 ].…”

Directed evolution driving the generation of an efficient keratinase variant to facilitate the feather degradation

“…Keratinase is a specific protease produced by microorganisms that exclusively degrades keratin waste, such as wool, feathers, bovine horn and so on. The keratinase-producing microorganisms are mainly bacteria, fungi and actinomycetes, most of which are screened from feather or hair piles (Bokveld et al 2021 ; Cao et al 2021 ). Among bacteria, the dominant keratinase-producing strain is Bacillus , such as Bacillus licheniformis PWD-1 that was firstly reported to be able to secrete keratinase to degrade feathers (Lin et al 1995 ).…”