| A new bacterial strain was isolated from soil in Changbai Mountain Jilin province as the thermostable protease producers. On the basis of the phylogenetic and phenotypic characteristics, the strain hould be placed in the genus Bacillus as a novel species for which we propose the name Bacillus sp. SD-05.The activity of thermostable protease was compared by culturing SD-05 in different liquid mediums. The optimal medium component for producing protease was decided.By culturing SD-05 in optimal medium, the optimum culture conditions for producing protease are decided as follows: 0.5% Casein, the initial pH 6.0, the 0.5%inoculation, 32℃, shaking at 130rpm and cultured for 24h.92.12% of the thermostable protease existed at the surface of cell and combined with cell membrane. Extraction means was studied. The optimal extraction means was that the cells was marinated in 60% of IPA for 2h then shaked in 50mmol/L PBS for 20h.A protease fraction was purified by the steps of ammonium sulfate fractionation, dialysis and Sephadex G-100 column chromatography. The protease purified from Sephadex G-100 showed a single band of protein with a molecular weight of 66000Da by SDS-PAGE.The optimum activity of protease was observed at the temperature of 60℃. The maximal hydrolysis of casein by the purified protease was observed at about pH 8.0. The protease is stable at pH6.0 -11.0 and at temperature below 60℃.
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