SCREENING AND CHARACTERIZATION KERATINASE ENZYME FROM BACTERIA IN KERATINOUS WAST

Abstract

Microbial keratinases are keratinolytic enzymes widely used in many industrial processes and management of wastes. This study was conducted with the aim of isolation of efficient keratinase producing bacteria form the soils of chicken feather-dumping sites and human hair-dumping places, determining optimum keratinase production conditions and partially characterizing the stability and activity of keratinase with regards to some physicochemical parameters. Plating of soil sample suspensions on chicken feather and human hair modified meal agar media resulted in the growth of three keratinolytic bacterial isolates (Kf1and Kf2 from poultry farm and Kh from hair cut dumping site) that were later identified as Bacillus species on the basis of their biochemical characteristics. The optimum temperature of keratinase production for all isolates was recorded at 60 0C with activities of 16.4 U/ml/min, 15.1U/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 the activities 14.3U/ml/min, 12.3 U/ml/min and 10.1U/ml/min for isolates Kf1, Kf2, and Kh, respectively. Regarding nitrogen sources, Yeast Extract gave maximum activities corresponding to 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 pH7 for all isolates with activities of 15.2 U/ml/min, 13.2 U/ml/min, and 11U/ml/min for Kf1, Kf2 and Kh isolates, respectively. The maximum keratinase stability time for the three isolates was found to be 48 hours with keratinase activity of 8.5U/ml/min, 6.5U/ml/min and 5.9 U/ml/min for Kf1, Kf2, and Kh . These results generally indicate that the keratinase obtained in this study belong to the class of hydrolases that are active and stable at neutral pH conditions. These enzymes were also less active and less stable at 800C for all isolates. Thus identification of the three Bacillus isolates at a molecular level and the purification as well as the detailed characterization of the types of keratinase is recommended for effective utilization in animal feed processing and other industrial applications.