Characterization of feather-degrading bacterial populations from birds’ nests – Potential strains for biomass production for animal feed

Feather degrading bacteria from birds’ nests were characterized to find safe bacterial strains that could be utilized to convert feathers into soluble form and bacterial biomass for feed purposes. Of all tested 571 isolates 122 were keratinolytic. Partial sequencing of the 16S rRNA gene revealed that the keratinolytic isolates represented Proteobacteria (genera Pseudomonas and Stenotrophomonas) and Firmicutes (genera Bacillus, Exiguobacterium, Paenibacillus, Rummeliibacillus, and Sporosarcina). Bacillus cereus group and gram-negative bacterial isolates were not further characterized due to safety concerns related to potential pathogenicity or potential exposure of animals or workers to endotoxins (lipopolysaccharide part of the gram-negative cell wall). Keratinolytic strains showed clear differences in their ability to solubilize feathers with feather weight losses up to 30%. Amino acid composition of feather hydrolysates shifted from feather composition towards more bacterial-like composition. Especially the levels of lysine could be increased in the feather hydrolysate with bacterial fermentation. Feathers can be effectively hydrolyzed with non-pathogenic bacteria without any additional nutrients. The resulting feather hydrolysate is easier to digest than feather material and it has an improved amino acid composition regarding some limiting amino acids. The amino acid content of the final product can be tailored by varying the fermentation time and thus the ratio of bacterial cells to the feather hydrolysate.