A fermentation process employing precursor‐directed biosynthesis is being developed for the manufacture of 6‐deoxyerythronolide B (6‐dEB) analogues. Through a plasmid‐based system in Streptomyces coelicolor, 6‐dEB synthesis is catalyzed by 6‐dEB synthase (DEBS). 6‐dEB synthesis is abolished by inactivation of the ketosynthase (KS) 1 domain of DEBS but can be restored by providing synthetic activated diketides. Because of its inherent catalytic flexibility, the KS1‐deficient DEBS is capable of utilizing unnatural diketides to form various 13‐substituted 6‐dEBs. Here we characterize process variables associated with diketide feeding in shake‐flask experiments. 13‐R‐6‐dEB production was found to depend strongly on diketide feed concentrations, on the growth phase of cultures at feeding time, and on the R‐group present in the diketide moiety. In all cases a major portion of the fed diketides was degraded by the cells.
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