Adsorption of glutamicum onto polysulphone membrane

Abstract

A systematic study on the influence of solution chemistry (pH, ionic strength) and bulk cell concentration on static and dynamic glutamicum adsorption onto polysulphone membrane, cell adsorption isotherms, and the rate of adsorption was performed. The interaction between cells and membrane surface in the absence of salt was dominated by electrostatic interaction due to the charges on the cell surface. The maximum adsorption occurred at isoelectric point (IEP) of cells, suggesting complementary electrostatically driven adsorption. At pH values below the IEP, adsorption increased as pH increased, but above the IEP, adsorption decreased as pH increased. Increased salt concentration reduces electrostatic repulsion between like-charged material (increasing adsorption) and decreases electrostatic attraction between oppositely charged material (decreased adsorption). Isotherms were performed to determine equilibrium adsorption behavior. Adsorption isotherms follow Langmuir laws, the parameters of which were determined. By taking into account electrostatic interactions, it has been possible to explain the evolution in the adsorption isotherms of the cell on the membrane surface with the solution chemical conditions. Rate of adsorption was determined by measuring adsorbed mass as a function of time at different pH values, ionic strength, and bulk feed concentration. In order to determine the effect of convective flow and electrostatic interactions on the cell adsorption behavior, static and dynamic adsorption were compared. Although convective forces tend to increase the amount of cell accumulated near the membrane surface, electrostatic interactions played a stronger role, as evident in the irreversible adsorption results for the static and dynamic cases. Controlling electrostatic interactions could reduce adsorption of cells onto the membrane, consequently reducing long-term membrane fouling.