English abstract
Chicken feathers are one of the greatest sources of keratin. These wastes, on the other
hand, can be converted into valuable resources. This current study was conducted to
valorize these keratinized wastes to produce microbial keratinase, using the microbes
present on feathers. 15 keratinolytic bacterial strains and 15 keratinolytic fungal strains
were isolated. Among the isolates from the feathers, Aeromonas caviae was identified as
an efficient keratinase producer. This bacterium showed high efficiency in feather
degradation (23 %) with a high enzyme activity of 42.59 U/mL at 72 h of cultivation. At
168 h of cultivation, A. caviae produced 182.5 µg/mL of soluble protein. This soluble
protein contained 18 amino acids with their derivatives including; histidine, glycine,
tryptophan, tyrosine, valine, and β-alanine, alanine, arginine, asparagine, creatine,
glutamine, glutathione, isoleucine, leucine, lysine, methionine, cystine, taurine, ornithine,
proline, and threonine. The keratinase production conditions were optimized using the
Response Surface Method. The obtained enzyme was partially purified using ammonium
sulfate precipitation and dialysis. Under optimum conditions of PH 9 and 80 °C a
keratinase activity of 48.54 U/mL was obtained. The partially purified keratinase was
characterized as a serine protease. It was activated by K+
, Mg2+, Zn2+, and Na+
, salts, and
solvents including, SDS, Triton X-100, DMSO, Isopropanol, and TWEEN 80 with a
notable increase in activity of 6-10%. H2O2, 2-Mercaptoethanol, and acetonitrile slightly
inhibited the activity of keratinase. Moreover, the results revealed the ability of obtainable
keratinase to degrade other substrates including casein, gelatin and skim milk with higher
relative activity than the control. This study showed that keratinase produced by A. caviea
isolated from chicken feathers is a promising tool for different industrial applications.
