Nutritional regulation of protease production by the feather-degrading bacterium Chryseobacterium sp. kr6

The effects of nutritional conditions on growth and protease production by the feather-degrading Chryseobacterium sp. kr6 were investigated. Higher growth was observed on feather-containing or tryptone (TR) medium when compared to casein (CA) or glucose-nitrogen (GN) base medium. Protease production occurred during growth on feather-containing and TR media, whereas no protease activity was detected on CA or GN medium, indicating that protease production is not constitutive, depending on the presence of specific complex nitrogen sources. Supplementation of whole feathers (WF) medium with glucose (WFG) or NH(4)Cl (WFN) did not result in major differences in growth and protease production, whereas soluble protein was lower in supplemented media. Glucose consumption and growth were higher on WFG than on GN medium, suggesting that the absence of a specific complex nitrogen source limited bacterial growth. On WF medium, this strain grew closely attached to the feather structures, initially on the barbules and subsequently on the feather rachis. It was observed, through zymogram analysis, that strain kr6 produced diverse proteolytic enzymes in response to different growth substrates. These results were confirmed by the differential behaviors of crude proteases towards protease inhibitors.