Fusion PCR-targeted tylCV gene deletion of Streptomyces fradiae for producing desmycosin, the direct precursor of tilmicosin

Tilmicosin is a semisynthetic macrolide antibiotic derived from tylosin. The disruption of tylCV gene from tylosin producer—Streptomyces fradiae would result in the accumulation of desmycosin, the direct precursor of tilmicosin. TylCV gene disruption cassette was constructed by fusion PCR. The tylCV replacement strain of S. fradiae was obtained through intergeneric conjugation between S. fradiae and E. coli. The antibiotic resistance cassette is flanked by yeast FLP recombinase target sequences for removal of the antibiotic resistance and oriTRK2 to generate unmarked, nonpolar mutation. After optimization of the culture conditions, the yield of desmycosin reached 7.3 g l−l in 5 l jar fermentor, which could be scale-up for industrial fermentation to produce large amount of desmycosin for semisynthesis of tilmicosin directly.