The Optimization And Regulation Of Fermentation Process For Erythromycin Production By Recombinant Saccharopolyspora Erythraea And The Preliminary Analysis Of Metabolic Flux

The great increase of market requirement for erythromycin derivatives expanded the production of pharmaceutical product erythromycin A. However, the relatively low erythromycin titer together with the relatively high impurity components and the high broth viscosity greatly decreased the competitiveness power of erythromycin in international market. Hence, in this paper, the erythromycin A was increased greatly and the broth viscosity was dramatically decreased through optimizing the medium components and the fermentation process.Firstly, industrial feather peptone was selected from several organic nitrogen sources as the optimal easily-metabolized organic nitrogen source for erythromycin fermentation. Furthermore, erythromycin titer was increased by 1.98% through regulating the concentration ratio of industrial feather peptone to soybean flour. Owing to the relatively high broth viscosity resulting from industrial feather peptone, the increase of fermentation temperature was investigated for decreasing the broth viscosity. When the fermentation temperature was controlled at 35?, the broth viscosity was decreased by 70.1%. Then the optimal medium and fermentation process was scaled up to 25 M3 fermenter, and the erythromycin titer was as high as 11434U/ml, which was nearly equvalent to that in 50L fermenter.Secondly, the substitution of soybean flour with soybean hydrate was proposed to decrease the broth viscosity since the cell was disrupted with high fermentation temperature and decreased the membrane transmission flux. By this strategy, the broth viscosity was decreased by 60% while erythromycin titer was little affected. Then a further research of substitution of soybean flour with (NH4)2SO4 was done and it was found that the phosphorus in soybean flour was the main factor causing high viscosity. Considered that high phosphorus could stimulate the strain growth and then lead to a high broth viscosity, we designed different media with different total phosphorus. The broth viscosity with the relatively low phosphorus content was effectively decreased and the erythromycin titer and the erythromycin A reached 12077 U/ml and 9040 U/ml respectively by feeding inorganic phosphate with the relatively low-phosphorus-content medium. The extracellular amino acids and organic acids revealed that high consumption of the amino acids for erythromycin biosynthesis and the relatively low organic acids content excreted into the broth were beneficial for the high erythromycin production.Finally, in order to decrease the glucose feeding rate of the fermentation by recombinant strain on industrial scale, a strategy of controlling culture pH after sterilization and feeding relatively low pH liquid sugar solution was proposed and the results showed that the average glucose feeding rate was decreased by 53%.The macro-metabolic analysis revealed that more glucose did not flow into the erythromycin flux, but was oxidized into CO2 in TCA cycle when high glucose feeding rate was employed in erythromycin fermentation.