The ultrafiltration process is used widely to eliminate impurities during the downstream processing from recombinant proteins. Two ultrafiltration buffers (citrate and phosphate) are commonly used in the industrial production of recombinant erythropoietin. The aim of this study was to investigate the effect of these two buffers on the purity and structure of purified recombinant erythropoietin. In this study, seven harvests were purified by gel filtration and ion-exchange chromatography. Then, the ultrafiltration process was performed. So, half volume of each sample was washed with phosphate buffer and the rest with citrate buffer under different conditions. Purified protein content was measured using the HPLC method. The progeny, CHO protein contamination, ds-DNA impurity, and endotoxin level tests were performed. Finally, the structure was investigated by a capillary zone electrophoresis method. The results showed that the amount of obtained proteins were 0.51, 0.46, 0.38, 0.27, 0.39, 0.29, 0.38 mg/ml, and 0.46, 0.38, 0.35, 0.23, 0.36, 0.25, 0.34 mg/ml by washing with phosphate and citrate buffers, respectively. Qualitative and structural tests were in acceptable range for all proteins. The results of the study demonstrated that buffer conditions can have a noticeable effect on the efficacy of ultrafiltration process.
