Abstract:
Bacillus paralicheniformis T7, which exhibits high proteolytic and keratinolytic activities, was isolated
from soil in Kazakhstan. Its secreted proteases were thermostable and alkaline, demonstrating
maximum activity at 70 °C and pH 9.0. The proteases and keratinases of this strain were sensitive to
Ni2+, Co2+, Mn2+, and Cd2+, with Cu2+, Co2+ and Cd2+ negatively affecting keratinolytic activity, and
Fe3+ ions have a strong inhibitory effect on proteolytic and keratinolytic activity. Seven proteases were
identified in the enzymatic extract of B. paralicheniformis T7: four from the serine peptidase family
and three from the metallopeptidase family. The proteases hydrolyzed 1 mg of casein, hemoglobin,
gelatin, ovalbumin, bovine serum albumin, or keratin within 15 s to 30 min. The high keratinolytic
activity of this strain was confirmed through the degradation of chicken feathers, horns, hooves, wool,
and cattle hide. Chicken feathers were hydrolyzed in 4 days, and the degrees of hydrolysis for cattle
hide, wool, hoof, and horn after 7 days of cultivation were 97.2, 34.5, 29.6, and 3.6%, respectively.
During submerged fermentation with feather medium in a laboratory bioreactor, the strain secreted
enzymes with 249.20±7.88 U/mL protease activity after 24 h. Thus, B. paralicheniformis T7 can be
used to produce proteolytic and keratinolytic enzymes for application in processing proteinaceous raw
materials and keratinous animal waste.
