Abstract：Bacillus subtilis FJ-3-16 is an efficient keratinase-producing bacterium strain and its extracellular keratinase has many prospective applications in livestock wastes degradation, animal furs dehairing, detergent additive and so on. In order to increase the industrial yield of the extracellular keratinase produced by the strain, its fermentative condition was optimized using one-variable-at-a-time method, Plackett-Burman (PB) design and central composite design (CCD). The optimized medium contained corn meal 1.41%, soybean flour 3.62%, casein 2%, CaCl2 0.16%, K2HPO4 0.3%, KH2PO4 0.1% (pH 8.0) and optimized condition was 48 h cultivation at 37 ℃ and a rotate shaking of 250 r/min. The total activity of the extracellular keratinase was increased from 73.82 to 166.08 U/mL. Then, the optimized cultivation condition was further amplified in 50 L fermenter. The total activity of the extracellular keratinase was further increased to 207.6 U/mL in the amplified 50 L fermenter, and meanwhile the fermentative time was reduced from 48 to 18 h. The dehairing capacity of the ferment toward the skins of the Bama pig's (Sus scrofa) hoof and head was also evaluated using enzymatic dehairing experiments. Pieces of skins obtained from the hoof and head of the Bama pig, and the whole hoof of the Bama pig were treated by the crude extracellular keratinase at 50 ℃ for 6 h, 10 h, respectively, and dehairing effects were obvious. This study would pave the way for the application of strain FJ-3-16 in pig dehairing.
