The marine Alteromonas sp. B-10-31 has been found to produce a very strong extracellular subtilisin inhibitor. We named this inhibitor “Marinostatin” and the optimal medium of strain B-10-31 for the production of Marinostatin was studied. Among various different nitrogen and carbon sources, 0.6% (w/v) polypepton (Daigo) proved to be the most effective nitrogen source and 0.05% (w/v) glucose stimulated the bacterial growth and production of Marinostatin. The maximum production (22.0 Unit/ml) was obtained at pH 6.0 in full strength seawater at 20°C and shaking for 24-33 hrs. The production of Marinostatin was almost parallel to the growth of the strain used. Unlike other protease inhibitors reported so far, Marinostatin was unstable in the stationary phase of growth due to the production of a proteolytic enzyme by the strain.
The crude Marinostatin was thermostable and showed a wide range of pH stability. It also exhibited inhibitory activity against a wide variety of proteases.