Overproduction of extracellular protease activity by Streptomyces C5-A13 in fed-batch fermentation

Summary Streptomyces C5-A13, a non-sporulating, pleiotropic mutant of the anthracycline-producing strain, Streptomyces C5, overproduces extracellular proteolytic activity against the substrate azocasein. This extracellular protease activity was produced primarily during the stationary phase. This appears to be an effect related to growth rate rather than to glucose repression, because only very high concentrations of glucose appear to inhibit protease synthesis. Production of extracellular protease activity was stimulated by the presence of carbonate anions in the medium. The optimal concentration of soluble carbonate was 60–80 mM and the stimulation by carbonate was shown not to be due to a pH effect. Approximately 3200–3500 units of extracellular azocaseinase activity were produced per millititre of culture broth using partially optimized fed-batch fermentation processes. This value represents about ninefold greater activity than produced under shake flask conditions.