Effects of Operating Conditions on the Purification of Protein in Centrifugal Filtration of Bio-Suspensions

Abstract

The purification of BSA from yeast/BSA binary suspension using batchwise centrifugal filtration under various conditions is studied. Effects of suspension pH and rotational speed on the cake properties, filtration rate and protein recovery are discussed. The experimental results indicate that the filtration rate is significantly affected by the cake growth at the initial periods of filtration, and no evident rate difference can be found among different suspension pH values under a low rotational speed. However, the effect of cake compression becomes more dominant as rotational speed increases. The compression of yeast cake is irreversible and strongly affected by the suspension pH especially under a high rotational speed. The cakes formed at pH 3.0 possess the highest compressibility due to the yeast coagulation, while the average specific resistance of cake is the lowest at pH 7.0 because of the high zeta potential of yeast cells. In addition, the recovery of BSA can be as high as 95–98% under the operating conditions of this study. Since the BSA concentration in the filtrate keeps constant during the filtration under various rotational speeds, the recovery of BSA is dependent solely on the filtration rate in spite of the little adsorbed amount on the yeast cells. To operate under higher rotational speed and pH 7.0 is optimal from the viewpoint of economic operation time and protein recovery.