Protease production by Streptomyces thermovulgaris grown on rapemeal-derived media

A range of actinomycete species was tested for their ability to grow on particulate and particle-free rapeseed meal-derived media. Streptomycetes grew on both types of medium and produced a number of extracellular enzymes. Highest activities of protease were produced by Streptomyces thermovulgaris and reflected the high available protein content of rapemeal. Enzyme production and growth were analysed in fermentor-grown batch cultures of S. thermovulgaris using the particle-free rapemeal broth termed medium B. Growth was biphasic and the majority of the protease was produced during the second slower phase. Analysis of the protease as azocaseinase activity revealed a high degree of thermostability in the presence of calcium such that approximately 20% of the activity remained after incubation at 70°C for 24 h. Gel filtration suggested that S. thermovulgaris synthesized more than one kind of protease and this was confirmed by using specific peptide substrates and inhibitors which revealed the presence of distinct serine and metallo-type enzymes.