Optimization of antibiotic production by the cyanobacteriumScytonema sp. TISTR 8208 immobilized on polyurethane foam

The cyanobacteriumScytonema sp. TISTR 8208 was cultivated under illumination with a polyurethane foam sheet as the biomass-supporting material. The cyanobacterium produced an antibiotic with a broad spectrum in the post-exponential phase of growth. Modification of the composition of the BGA medium by adding 1.5 g 1^?1 NaNO₃, increasing the Fe₂(SO₄)₃.6H₂O concentration to 0.025 g 1^?1 not adding NaCl, using an initial pH of 7.0, incubated at 35 °C, and at the light intensity of 90 µmol photon m^?2 s^?1, enabled a 28-fold increase in antibiotic production. The antibiotic was stable when treated at 70 °C for 2 h and unstable at 100 °C for 75 min. Since the activity was completely lost with protease treatment and the positive result was shown toward ninhydrin test, and the UV and IR spectrum were characterized at 210 nm and 1547 cm^?1, respectively, this antibiotic appears to be a peptide with aromatic amino acid. Analysis by double-focusing mass spectrometry showed the molecular weight of the antibiotic to be 1490.