Alkaline keratinase from sp. DRS4 efficiently biodegrades chicken feathers to synthesize improved keratin/bacterial nanocellulose-based bioplastics.

Chicken feathers represent an abundant and sustainable resource that can be harnessed for multiple value-added products. Bioplastic reinforced with bacterial nanocellulose was synthesized using enzymatically digested chicken feathers. A highly efficient keratinolytic bacterium, identified as sp. DRS4 through biochemical characterization and 16S rRNA gene sequence analysis, was isolated from deposit soils of Lake Chitu in Ethiopia. sp. DRS4 was able to completely degrade chicken feathers within 48 h. Optimization of the physicochemical parameters increased the enzyme yield from sp. DRS4 by 30%. The enzyme showed optimal keratinolytic activity at 37 °C and pH 11, hydrolyzing white chicken feathers in 72 h and providing hydrolysates with a total protein content of 251.145 mg/mL. Further, the mechanical and thermal properties of a bioplastic made from hydrolysates and reinforced with bacterial nanocellulose were assessed. The bioplastic exhibited a remarkable tensile strength of 5.769 MPa and reached a melting temperature of 127.5 °C, suggesting that bacterial nanocellulose acts as an effective stabilizer. Fourier Transform Infrared spectroscopy (FTIR) analysis revealed additional peaks in BNC-reinforced plastic films, indicating a binding interaction that enhanced the bioplastic properties. Overall, sp. DRS4 is a potential strain for alkaline keratinase production and a promising candidate for upgrading chicken feathers into high-value-added products.