Study On Preparative Chromatographic Separation Of Erythromycin A And Erythromycin C By Macroporous Resin

With the continuous development of semi-synthetic erythromycin drugs and a widely uses in clinical medicine, erythromycin thiocyanate A, as an antibiotic API, has been increasingly important. Since the purity of erythromycin thiocyanate A has a great impact on the yield and quality of the semi-synthetic erythromycin drugs, it has a strict requirement. With high-yield genetically engineered bacterium applied extensively, the concentration of erythromycin in fermentation broth had been increased a lot and energy consumption was cut down, but, at the same time, erythromycin C which has low antimicrobial activity and high toxicity were accumulated. So separating erythromycin C effectively is a new challenge. However, solvent extraction as the common way for purification of erythromycin A is ineffective to separate erythromycin A and erythromycin C, and the impurity of erythromycin C can’t be removed effectively.The basic data and process of the separation of erythromycin A and erythromycin C were studied in this paper. Solution polarity were adjusted in order to increase the adsorptive selectivity of erythromycin A. Competitive adsorption equilibrium behavior in batch mode and adsorption mass transfer process on fixed-bed of erythromycin A and erythromycin C in the binary system using macro-porous resin SP825were investigated systematically. Then, an innovative process based on frontal chromatography and special eluent washing was proposed to purify and obtain erythromycin thiocyanate A from erythromycin fermentation broth with high content of impurity erythromycin C. This process is environmental friendly, economic and suitable for large-scale production.The main contents and results of this research are included below:(1) The influence of the polarity of erythromycin solution on adsorptive selectivity of erythromycin A over erythromycin C was studied in detail. The suitable solvent was phosphate buffer with3%(v/v) ethyl acetate. Washing chromatography and frontal chromatography were investigated comparatively. It showed that frontal chromatography was more suitable for the separation of erythromycin A and erythromycin C than washing chromatography in industrial application.(2) The effects of the polarity of erythromycin solution on adsorption behavior of erythromycin A and erythromycin C on SP825at different temperatures were discussed by batch adsorption equilibrium experiments. By using competitive Langmuir adsorption isotherms to fit the equilibrium data, it showed that this model could describe the competitive adsorption equilibrium of erythromycin A and erythromycin C on SP825well. Selective coefficient of erythromycin A and some thermodynamic parameters of both erythromycin A and erythromycin C were calculated.(3) The influences of feed concentration and flow rate on breakthrough behavior of erythromycin A and erythromycin C were studied on SP825in fixed bed. A general rate model was established with the consideration of all the effects including axial dispersion, film diffusion and pore diffusion. The model fitted well with the experimental breakthrough curve. The effects of axial diffusion coefficient, film diffusion and pore diffusion of both erythromycin A and erythromycin C on the penetration behavior of erythromycin A and erythromycin C were also investigated in details. It was found that axial dispersion and pore diffusion affected the adsorption behavior of both erythromycin A and erythromycin C greatly, while film diffusion did slightly.(4) An innovative purification process was proposed to separate and purify erythromycin thiocyanate A from its fermentation broth based on adsorption chromatography with macro-porous resin. It mainly includes the following steps:separating erythromycin A and erythromycin C by frontal chromatography、washing impurities in the bed、eluting erythromycin A, washing erythromycin C in the eluent and obtaining the product by reactive crystallization. In the process, two original steps could separate erythromycin C effectively, which are adsorbing erythromycin A by frontal chromatography and using phosphate buffer to wash the eluent. Content of erythromycin A and erythromycin C in erythromycin thiocyanate A obtained by this process and solvent extraction accompanied with salt precipitation method were compared, and the former could separate erythromycin C more effectively.