Abstract:In order to screen a wild-type strain with high alkaline protease activity and good stability, and to achieve industrial-scale production of protease, a stable high-yield salt-tolerant alkaline protease-producing strain was isolated from seawater of the East China Sea in the Lin'gang region of Shanghai. The morphological characteristics, physiological characteristics, and 16S rDNA gene sequence of the strain were analyzed and sequenced, and the strain was identified as Bacillus stratosphericus and named B. stratosphericus LK-3. The enzymatic properties study revealed that the optimal conditions for enzyme action were 35 ℃, pH 8.5, and inoculation amount of 7%. Under these conditions, the enzyme activity reached （581.74±0.81） U/mL after 72 h fermentation. In addition, the enzyme showed good salt tolerance and maintained 22.03% of the relative original enzyme activity even under a high saturated salt concentration of 40 g/dL. The salt tolerance of protease is a valuable characteristic, and the alkaline protease produced by strain LK-3 could be purified and used as a biological detergent additive in industrial production.
