Production of Bacterial Keratinase from Keratinous Waste

Abstract

This study was conducted with the aim of isolation of efficient keratinase producing bacteria from the soils of chicken feather and human hair-dumping places, determining optimum keratinase production conditions and partially characterizing the stability of keratinase interms of keratinase activity assay with regards to some physicochemical parameters. Inoculation of soil sample suspensions on chicken feather and human hair modified meal agar plate resulted in the growth of three keratinolytic bacterial isolates (Kf₁and Kf₂ from chicken feather and Kh from hair cut dumping sites). These isolates were identified as Bacillus species on the basis of their biochemical characteristics. The optimum temperature of keratinase production for all isolates was recorded at 60°C with activities of 16.2 U/ml/min, 15.5U/ml/min and 12.3 U/ml/min for isolates Kf₁, Kf₂ and Kh, respectively. In all cases, pH 7 was optimum for keratinase production resulting in activities corresponding to 16.4 U/ml/min, 15.1U/ml/min and 12.4/ml/min for Kf₁, Kf₂ and Kh, respectively. Among the various carbon sources tested, potato gave 14.3 U/ml/min, 11.3 U/ml/min and 10.1U/ml/min for isolates Kf₁, Kf₂, and Kh, respectively. Regarding nitrogen sources, yeast extract gave 25.2 U/ml/min, 20.5 U/ml/min and 16.37 U/ml/min for Kf₁, Kf₂, and Kh, respectively. Studies on the effect of pH on the activity and stability of keratinase enzyme revealed that the crude enzyme had a maximum stability at pH 7.The maximum keratinase stability time for the three isolates was found to be 48 hr with keratinase activity of 8.5 U/ml/min, 6.5 U/ml/min and 5.9 U/ml/min for Kf₁, Kf₂, and Kh, respectively. These results generally indicate that the keratinase obtained in this study belongs to the class of hydrolases that are active and stable at pH 7. Thus, identification of the three Bacillus isolates at a molecular level and separation and identification of the types of keratinase produced by molecular techniques is recommended.