Abstract:

The optimal fermentation conditions for producing low-temperature alkaline protease by a marine bacterium (Pseudoalteromonas flavipulchra HH407) from Lianyungang sea area and some enzymatic properties of this enzyme are reported in this article. The highest enzyme production was achieved at the conditions of fermentation temperature of 20 ℃, pH 8.0, NaCl concentration of 20 g/L, inoculum amount of 2.5% and medium volume in fermentation tank of 20%. Meanwhile, enzyme production was improved by adding mannitol, fructose, lactose, sucrose, maltose, fishmeal and yeast extract. The optimal reaction temperature for this protease was 35 ℃. The relative enzyme activity was 21.7% at 0 ℃ and 80% after incubation at 45 ℃ for 60 min. The optimal pH for this protease was pH 10.0. A high level of relative activity could be remained in the pH range of 7.0 to 11.0. This protease was stable in the range of pH 8.0 to 11.0. Therefore, it is a low-temperature alkaline protease. Moreover, its activity was stimulated in the presence of Mn2+, Cu2+ and Ca2+, and inhibited in the presence of Hg2+ and PMSF, but was not affected by EDTA. These investigations suggest that this protease might be a serine protease.

Key words: Pseudoalteromonas flavipulchra HH407, low-temperature protease, enzymatic property, protease production condition