Exploration of Thermophilic Keratinolytic Bacteria from Air Putih Hot Spring, Bengkulu, for Poultry Feather Bioconversion

Rapid growth of Indonesia’s poultry sector has increased the accumulation of feather waste composed of recalcitrant keratin. This study represents the first exploration of thermophilic keratinolytic bacteria from the unexplored Air Putih Hot Spring, Lebong, Bengkulu, Indonesia, and evaluates their keratinase activity for poultry feather bioconversion. Isolates AAL2, AAL3, ABL3, and SCL2 were screened on feather-based keratin agar at 50 °C for 48 h. Keratinolytic activity was evaluated qualitatively using the keratinolytic index (KI) and quantitatively using the Folin method. Morphological characterization and molecular identification using 16S rRNA sequencing, BLAST, and Neighbor-Joining phylogenetic analysis were performed. All isolates produced clear zones, with isolate AAL3 showing the highest KI value (2.8). Keratinase activities were 1.0074 U/mL (AAL3), 0.5931 U/mL (AAL2), 0.7493 U/mL (ABL3), and 0.9527 U/mL (SCL2). All isolates were identified as Gram-positive, endospore-forming bacilli belonging to the genus Bacillus. Phylogenetic analysis showed that AAL2 was closely related to Bacillus mojavensis, while AAL3, ABL3, and SCL2 were closely related to Bacillus licheniformis ATCC 14580. These findings demonstrate the potential of thermophilic keratinolytic bacteria for sustainable feather waste bioconversion, amino-acid-rich hydrolysate production, and environmentally friendly biomaterial development supporting circular economy-based waste management.