A10255, a complex of novel growth-promoting thiopeptide antibiotics produced by a strain of Streptomyces gardneri. Taxonomy and fermentation studies.

A10255 is a complex of new thiopeptide antibiotics characterized structurally by a cyclic peptide core to which is attached a side chain composed of dehydroalanine moieties. The complex contained 80-85% factor B, 15-20% factor G, and trace amounts of factors C, D, E, F, H, and J. Taxonomic studies indicated the producing microorganism to be a strain of Streptomyces gardneri. The major portion of the antibiotic produced remained associated with the mycelial biomass, from which it was extracted with polar solvents such as aqueous methanol or aqueous acetone. Initial A10255 yields of < 2 micrograms/ml were increased to over 300 micrograms/ml in stirred reactors through strain selection, nutritional studies, and conversion of the batch fermentation to a fed-batch mode.