Keratinolytic potential of Bacillus licheniformis RG1: structural and biochemical mechanism of feather degradation

Keratinolytic Bacillus licheniformis RG1 was used to study the mechanism of keratinolysis. Scanning electron microscopy studies revealed that bacterial cells grew closely adhered to the barbules of feathers, completely degrading them within 24 h. Biochemical studies indicated that the Bacillus strain produced an extracellular protease, which had keratinolytic potential. The extracellular keratinolytic activity (425 U) was synergistically enhanced by the addition of intracellular disulfide reductases (1712 U). However, these enzymes alone (keratinase and disulfide reductase), without live bacterial cells, failed to degrade the feather. Complete feather degradation was obtained only when living bacterial cells were present, emphasizing that bacterial adhesion plays a key role during the degradation process. The bacterial cells probably provide a continuous supply of reductant to break disulfide bridges. In addition, sulfite detected in the extracellular broth during feather degradation indicated that sulfitolysis may also play a role in feather degradation by the bacterium.