From various soil and water samples collected from Do Son - Hai Phong the bacteria producing keratinase were isolated and screened. Among them, the best keratinase producer designated as DS23 showed a great growth rate, a strong keratinase activity and be able to develop in a great numbers of growing media. The strain DS23 was first identified as Bacillus branch using the API 50CHB kit whereas its 16s rRNA gene sequence similarities were 99 percent with B. licheniformis. The optimum conditions for keratinase activity of this train DS23 were pHS, 37°C, in the medium containing per litre: glucose 10.0
peptone 10.0
K2HPO4 1.0
MgSO4.7H2O 0.2
Na2CO3 3.0 with 0.3 percent keratin solube as keratinase inductor and the initial bacteria concentration of 2 percent. The best keratinase activity of 63.8 U/ml was obtained after 72 hours of incubation. The crude enzyme from culture medium incubated was able to hydrolyze the native feather.