Proteolytic and non-proteolytic mechanisms of keratin degradation in Onygena corvina revealed by a proteogenomic approach

Summary

Feathers and wool from the poultry and textile industries create massive waste problems because they are very difficult to break down. Researchers discovered that a fungus called Onygena corvina can break down these tough materials using a sophisticated combination of over 70 different proteins. The fungus doesn’t just use cutting enzymes (proteases) but also uses helper proteins that weaken the structure first by removing chemical modifications and breaking certain chemical bonds. Interestingly, the fungus is even more effective when given both feather and wool together, suggesting these waste streams could be processed simultaneously.

Background

Keratin-rich byproducts from poultry, textile, and leather industries present significant waste management challenges due to their recalcitrant nature. Microbial degradation offers a promising sustainable solution, but the complex enzymatic mechanisms required remain incompletely understood. Onygena corvina is a non-pathogenic saprophytic fungus known for efficient keratin degradation.

Objective

To comprehensively characterize the keratinolytic machinery of Onygena corvina using a proteogenomic approach. This study aimed to identify both proteolytic and non-proteolytic mechanisms involved in degrading α-keratin (wool) and β-keratin (feathers).

Results

O. corvina secretes 73 putatively secreted proteins including 30 proteases (primarily serine and metalloproteases) and numerous accessory enzymes such as oxidoreductases, phosphatases, esterases, and sialidases. The fungus employs substrate-specific enzyme induction for different keratin types and achieves 95% degradation efficiency when cultivated on combined feather and wool substrates compared to 70% on individual substrates.

Conclusion

Keratin degradation by O. corvina involves both proteolytic and non-proteolytic mechanisms including mechanical keratinolysis, removal of post-translational modifications, and disulfide bond reduction. The synergistic enzyme interactions and substrate-specific responses highlight the complexity of microbial keratin degradation and inform development of improved biotechnological approaches for keratin valorization.
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