High-throughput optimization of the chemically defined synthetic medium for the production of erythromycin A

Erythromycin A is an important antibiotic. A chemically defined synthetic medium for erythromycin production was systematically optimized in this study. A high-throughput method was employed to reduce the number of components and optimize the concentration of each component. After two round single composition deletion experiment, only 19 components were remained in the medium, and then the concentration of each component was optimized through PB experiment. The optimal medium from the PB experiment was further optimized according to the nitrogen and phosphate metabolic consumption in 5 L bioreactor. It was observed that among the 8 amino acids concluded in the media, 4 amino acids were first consumed, when they are almost depleted, the other 4 amino acids were initiated their consumption afterwards in 5 L bioreactor. The decrease of phosphate concentration would increase q_glc and q_ery. However, when phosphate concentration was too low, the production of erythromycin was hindered. The positive correlation between intracellular metabolite pools and Y_ery/glc indicated that low phosphate concentration in the medium can promote cell metabolism especially secondary metabolism during the stationary phase; however, if it was too low (5 mmol/L), the cell metabolism and secondary metabolism would both slow down. The erythromycin titer in the optimized medium (medium V) reached 1380 mg/L, which was 17 times higher than the previously used synthetic medium in our lab. The optimized medium can facilitate the metabolomics study or metabolic flux analysis of the erythromycin fermentation process, which laid a solid foundation for further study of erythromycin fermentation process.