Twenty-seven of one hundred thirty-five marine actinomycete …….isolates were producers. Analysis of the 16S rRNA gene of the most potent bioactive isolate showed a strong similarity with Saccharomonospora viridis AHK190. For the production of antimicrobial metabolites, nutritional and environmental conditions have been optimized. Maximum antibiotic production was obtained when galactose was used as a sole carbon source at a concentration of 4.5% (w/v) in the presence of 7% (w/v) aspartic acid with salinity level 3% (w/v) and K₂HPO₄ at 0.011%. Similarly, initial medium pH of 8.0, incubation temperature of 55°C and incubation period of 72 hr were found to be the optimum. The chemical structure of this compound was elucidated on the basis of its spectroscopy data, elemental analysis, and its molecular formula was found to be  C₃₁H₃₄O₄S₃. The minimum inhibitory concentration of the pure compound against the tested bacteria was found to be in the range of 125-250 μg/ml and the minimum bacteriocidal concentration of the purified antibiotic was ranged between 250 and 500 μg/ml. For fungi, the minimum inhibitory concentration was ranged between250-500µg/ml. The pure compound also found to have cytotoxic activity against human colon carcinoma with lethal concentration 50 of 24.2µg/ml.