The Regulation And Optimization Of Erythromycin Fermentation By Recombinant Saccharopolyspora Erythraea And The Application Of Biomass Monitor To Its On-line Process Control

Erythromycin is a macrolide antibiotic. The researchers have done a lot of studies to improve the industrial level of erythromycin fermentation and optimize the component as well, with the global increasing demand of erythromycin. In this paper, the regulation of nitrogen and phosphorus and the process optimization of feeding strategy on glucose and propanol were carried out by erythromycin fermentation in 50 L fermentor. First of all, according to the problem of high viscosity and high glucose consumption encountered by ZL1004 strain in the late fermentation process, we combined ammonium sulfate and soybean powder as nitrogen source to solve it successfully. The viscosity had a 40% reduction compared with the control group and the glucose consumption was nearly 40% lower than the control. The glucose consumption of fermentation process could be controlled by increasing the concentration of the physiological acidic substances of ammonium sulfate. It was found that the viscosity of experimental group was lower in the whole fermentation process and the decrease of glucose consumption was also very obvious by reducing the concentration of soybean powder and controlling the late release of phosphorus from it. In addition, it was feasible to replace the 6 g/L yeast powder with 0.5 g/L inorganic phosphorus KH2PO4 at 1 g/(L·h) flow rate under the concentration of 10 g/L KH2PO4.In this paper, for the first time on-line viable biomass monitor was applied in the erythromycin production to assist in dynamic optimizing the ratio of glucose and propanol. It was found that the capacitance values were sensitive to the variation of biomass and microbial morphology as well as the true state of cell growth. The experimental results showed that the high residual propanol concentration (more than 1.52 g/L) had an inhibition on the cell growth. It was most favorable to both cell growth and secondary metabolism to keep the ratio of glucose to propanol at 4.3. The specific growth rate calculated by the capacitance measurement correctly and accurately reflected the cell physiological state, clearly distinguished cell growth phase from erythromycin synthesis phase. An appropriate feed rate of propanol was crucial for cell growth and secondary metabolism, as well as to improve the quantity of erythromycin-A. When the propanol feed rate was at 0.125 g/(L·h) with a ratio of glucose and propanol at 4.3, the titer of erythromycin was 10500 U/ml with Ery-A:Ery of 0.85. In addition, the erythromycin production was further enhanced by 4%(10950 U/ml) when the propanol feed was regulated by stages based on both OUR and the on-line monitoring capacitance.Finally, a new recombinant strain HL7 was investigated. The experiment found that the amylase and protease activity of HL7 were weaker than that in ZL1004 with poor glucose utilization and more mycelia were found. The viscosity of HL7 fermentation was high with high requirements for oxygen supply. According to the easy-to-autolysis characteristics of HL7, the optimization of fermentation process was carried out. It was summarized from the experiment results that adding organic nitrogen source was beneficial to prolong the cell growth and increase the yield of erythromycin. The technique with less feeding frequency was more conducive to bacteria in the mid-late phase of erythromycin production. The Ery-C was reduced by feeding ammonium sulfate in yeast powder formula while the erythromycin titer was still close to the original level. The concentration of soybean powder could not be reduced too much in order to keep enough amino acids to be utilized in the late phase of fermentation.