Applied Microbiology and Biotechnology, Vol.104, No.10, 4359-4369, 2020
Genome shuffling based on different types of ribosome engineering mutants for enhanced production of 10-membered enediyne tiancimycin-A
Tiancimycin-A (TNM-A) is an anthraquinone-fused ten-membered enediyne produced by Streptomyces sp. CB03234, which is very promising for the development of anticancer antibody-drug conjugates (ADCs). To improve the titer of TNM-A, we have generated high-producing mutants CB03234-S and CB03234-R through ribosome engineering, but still not sufficient for pilot production of TNM-A. As the follow-up work, gentamycin-induced ribosome engineering was further adopted here to generate the mutant CB03234-G, which produced similar level of TNM-A as in CB03234-S and CB03234-R. Benefiting from the distinct antibiotic resistances of three ribosome engineering mutants, genome shuffling between any two of them was respectively carried out, and finally obtained the recombinant CB03234-GS26. Under optimal conditions, CB03234-GS26 produced 40.6 +/- 1.0 mg/L TNM-A in shaking flasks and 20.8 +/- 0.4 mg/L in a scaled-up 30-L fermentor. Comparing with the parental high-producing mutants, the over 1.6-fold titer improvement of CB03234-GS26 in fermentor was more promising for pilot production of TNM-A. Besides the distinctive morphological features, genetic characterization revealed that CB03234-GS26 possessed 1.8 kb rsmG related deletion just the same as CB03234-S, but no mutation was found in rpsL. Subsequent knockouts proved that rsmG was unrelated to titer improvement of TNM-A, which implied other genomic variations and mechanisms rather than ribosome engineering to enhance the biosynthesis of TNM-A. Therefore, CB03234-GS26 provided a basis to locate potential novel genetic targets, and explore the interactions between complex metabolic network and TNM biosynthetic pathway, which shall promote future construction of high-yielding systems for TNM-A and other anthraquinone-fused enediynes.
Keywords:Anthraquinone-fused enediyne;Ribosome engineering;Genome shuffling;Titer improvement;Scaled-up fermentation