PRODUCTION OF A THERMOPHILIC, EXTRACELLULAR ALKALINE PROTEASE BY BACILLUS-STEAROTHERMOPHILUS AP-4

A thermophilic Bacillus stearothermophilus strain AP-4 excreting a thermostable alkaline protease, was isolated from a local compost. Maximum activity of protease (250 U/ml) was after 36 h growth in broth at pH 9.0 and at 55-degrees-C. The protease was optimally active at pH 9.0 and 55-degrees-C and was stable in 5 mM CaCl2. The enzyme was completely inactivated by PMSF, EDTA and beta-mercaptoethanol. It is therefore a metal ion-dependent, alkaline, serine protease.