Abstract:A keratinase-producing strain of Bacillus isolated from the alimentary tracts of snakes was classified as Bacillus cereus YSQ08. The alkaline protease aprA gene (1194 bp) of this strain was studied by analyzing the genome and proteinase families of Bacillus cereus ATCC 14579, and the purified keratinase from Bacillus cereus YSQ08 was characterized. The aprA from Bacillus cereus YSQ08 was cloned, optimized, and expressed in recombinant Pichia pastoris X33 for further studying its potential keratinase abilities. After 10-fold concentration, the keratinolytic activity of the recombinant Pichia pastoris X33 was found to be 122.60 U/mL. The aprA protein displayed on the cell surface of Pichia pastoris X33 showed higher keratinolytic activity of 295.78 U/g. The results of the characterization indicated that the optimum conditions for the enzymatic reaction were pH 8.0 at 55 ℃. The presence of Fe2+ significantly increased the keratinase activity of the recombinant aprA protein by 329.08%. The surface-displayed aprA protein was immobilized as a whole-cell catalyst; this had higher thermostability at a lower cost of purification and recycling.
