STUDIES ON THE BREEDING OF ALKALINE PROTEASE PRODUCING STRAIN AND ITS SUBMERGED FERMENTATION CONDITIONS

A higher yield strain Bacillus pumilus 2080 was obtained by UV mutagenesis from Bacillus pumilus 1.894 for the production of alkaline protease. Subsequently, submerged fermentation( SmF) conditions and partial characterizations of alkaline protease from the mutant strain were investigated. The optimal medium contained(%): rapeseed meal 1.5, casein 1, D-fructose 1, KH2PO4 0.1, MgSO4·7H2O 0.02, CaCl2·2H2O 0.01, pH 8.5. After inoculated and incubated at 30 ℃ for 84 h by SmF, the maximum alkaline protease yield of 4.04×106 U/L was obtained from Bacillus pumilus 2080. The highest activity of the crude enzyme from Bacillus pumilus 2080 is at pH 10 and 50 ℃ respectively. The enzyme was stable not only from pH 8 to pH 10 at 40 ℃ for 30 min, but also from 30 ℃～45 ℃ for 30 min in Na2CO3/NaHCO3 buffer(0.1 mol/L, pH10).