Characterization of the Keratinolytic Activity of Three Streptomyces Strains and Impact of Their Co-Cultivation on This Activity

In this study, we describe the characterization of three efficient chicken feather-degrading Streptomyces bacteria isolated from honeybee samples and assess the impact of their co-cultivation on this activity and antistaphylococcal activity. Streptomyces griseoaurantiacus AD2 was the strain showing the highest keratinolytic activity (4000 U x mL(-1)), followed by Streptomyces albidoflavus AN1 and Streptomyces drozdowiczii AD1, which both generated approximately 3000 U x mL(-1). Moreover, a consortium constituted of these three strains was able to use chicken feathers as its sole nutrient source and growth in such conditions led to a significant increase in antibiotic production. S. griseoaurantiacus AD2 was the only strain that exhibited weak antimicrobial activity against Staphylococcus aureus. UPLC analyses revealed that a significant number of peaks detected in the extracts of co-cultures of the three strains were missing in the extracts of individual cultures. In addition, the production of specialized metabolites, such as undecylprodigiosin and manumycin A, was clearly enhanced in co-culture conditions, in agreement with the results of the antimicrobial bioassays against S. aureus. Our results revealed the benefits of co-cultivation of these bacterial species in terms of metabolic wealth and antibiotic production. Our work could thus contribute to the development of novel microbial-based strategies to valorize keratin waste.