Production of a fibrinolytic enzyme by thermophilic Streptomyces species

A strong fibrin-specific fibrinolytic enzyme was purified from the cell-free spent culture broth of a thermophilic organism, Streptomyces megasporus SD5. The strain could produce 150 mg crude protein per litre of spent broth, with a specific activity of 80 IU (Plough units) per milligram, within 18 h of incubation at 55 degreesC in glucose yeast/extract/peptone (GYP) medium, pH 8.0. For production of the enzyme, the strain could utilize different carbon and nitrogen sources with a C:N ratio of similar to 1:2. The enzyme was stable at a broad range of pH ranging from 5 to 9, and highly thermostable with 50% activity after storage at 60 degreesC for 6 months. The enzyme belonged to the serine endopeptidase group. In vitro clot lysis revealed that the enzyme was active at 37 degreesC.