Ribosome engineering and fermentation optimization leads to overproduction of tiancimycin A, a new enediyne natural product from Streptomyces sp. CB03234.

Tiancimycin (TNM) A, a recently discovered enediyne natural product from Streptomyces sp. CB03234, showed rapid and complete killing of cancer cells and could be used as a payload in antibody drug conjugates. The low yield of TNM A in the wild-type strain promoted us to use ribosome engineering and fermentation optimization for its yield improvement. The Streptomyces sp. CB03234-R-16 mutant strain with a L422P mutation in RpoB, the RNA polymerase β-subunit, was obtained from the rifamycin-resistant screening. After fermentation optimization, the titers of TNM A in Streptomyces sp. CB03234-R-16 reached to 22.5 ± 3.1 mg L-1 in shaking flasks, and 13 ± 1 mg L-1 in 15 L fermentors, which were at least 40-fold higher than that in the wild-type strain (~ 0.3 mg L-1). Quantitative real-time RT-PCR revealed markedly enhanced expression of key genes encoding TNM A biosynthetic enzymes and regulators in Streptomyces sp. CB03234-R-16. Our study should greatly facilitate the future efforts to develop TNM A into a clinical anticancer drug.