Identification and characterization of feather-degrading bacteria from keratin-rich wastes

In this study we aimed to isolate and identify bacteria showing high keratinolytic activity from different sources of decomposed poultry waste and soil in Shiraz, Iran. Initial screening identified 30 bacteria showing high proteolytic activity, which were selected for transfer to basal feather medium using feathers as the sole source of carbon, nitrogen and sulfur. The keratinolytic activity of the 13 isolates growing well on this medium was assayed using keratin azure as substrate. All isolates were identified based on 16S rDNA as a molecular marker. Of these, Bacillus sp. MKR5 exhibited the highest keratinolytic activity (225 U/ml), and was selected for further characterization. MKR5 demonstrated growth over a wide range of temperature (20–50°C). Complete feather degradation was achieved within 24 h at 40°C. This strain produced a thermostable keratinase with optimum activity at 70°C and pH 8.0. Enzyme activity was increased significantly by using 2-mercaptoethanol as a reducing agent. The keratinase was activated substantially in the presence of Co 2+ , Mg 2+ , TritonX-100, Tween-80 and EDTA, whereas SDS had a negative effect on enzyme activity. The thermostability of this enzyme makes it feasible to take advantage of this bacterium in biotechnological processes.