TAR cloning and integrated overexpression of 6-demethylchlortetracycline biosynthetic gene cluster in <italic>Streptomyces aureofaciens</italic>

6-Demethylchlortetracycline (6-DCT), a tetracycline antibiotic produced by Streptomyces aureofaciens, is a crucial precursor employed for the semi-synthesis of tigecycline, minocycline, and amadacyclin (PTK 0796). In this study, the 6-DCT biosynthetic gene cluster (BGC) was cloned from genomic DNA of a high 6-DCT-producing strain, S. aureofaciens DM-1, using the transformation-associated recombination method. An extra copy of the 6-DCT BGC was introduced and integrated into the chromosome of S. aureofaciens DM-1. Duplication of the 6-DCT BGC resulted in a maximum increase of the 6-DCT titer by 34%.