Sustainable Valorization of Poultry Slaughterhouse Waste Using <i>Bacillus</i> Strains Isolated from Poultry Manure

Traditional methods for managing poultry slaughterhouse waste, such as landfilling or incineration, are often costly and unsustainable. Therefore, identifying microbial strains capable of producing specific compounds that facilitate waste degradation has become essential. Bacillus strains were isolated from poultry manure and selected based on their enzymatic production capacity. Following molecular identification, <i>Bacillus</i> sp. B5J22-F and <i>Bacillus paramycoides</i> B4J22-F were selected for keratinolytic activity quantification and the evaluation of antibacterial activity under varying fermentation parameters. The studied strains exhibited optimal keratinolytic activity at pH 8 (33.0 U/mL for <i>B. paramycoides</i> B4J22-F and 24.9 U/mL for <i>Bacillus</i> sp. B5J22-F) and at a temperature of 45°C (43.6 U/mL for <i>B. paramycoides</i> B4J22-F). <i>Bacillus</i> sp. B5J22-F also achieved its peak activity at the same temperature (28.8 U/mL), demonstrating their effectiveness at elevated temperatures a critical factor in composting processes. Regarding antimicrobial assays, <i>B. paramycoides</i> B4J22-F exhibited the highest inhibition zone against <i>E. coli</i> at 30°C (10.2 mm) and pH 8 (9.1 mm). It also showed notable activity against <i>S. aureus</i> at 30°C (10.6 mm) and against B. cereus at pH 5 (12.9 mm), whereas Bacillus sp. B5J22-F displayed significant activity against <i>S. aureus</i> at pH 10 (14.5 mm). The <i>Bacillus</i> strains selected in this study demonstrated strong potential not only in keratin degradation but also in inhibiting the growth of certain pathogenic microorganisms. These findings support their potential use in the valorization of poultry slaughterhouse waste.