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26 PROCEEDINGS OF INTERNATIONAL SCIENTIFIC CONFERENCE ON APPLIED BIOTECHNOLOGY3.2. Isolation and structure determination of Ecumicin from ECUM libraryOf approximately 65,000 extracts from ECUM library were tested by MABA assay, and 349 (0.54%) extracts effected a >90% inhibition of fluorescence relative to that of the untreated control cultures. Such high activity was primarily found in the organic solvent extracts of normal or rich medium. Subsequent solidphase extraction on RP-18 cartridges and bioassay profiling by MABA assay lead to the isolation of ecumicin from the extracts of strain MJM5123 (Fig. 2).Figure 2. Screening of anti-tuberculosis compounds from ECUM libraryThe structure determination identified ecumicin as a macrocyclic tridecapeptide, as shown in Fig. 3.