Ion exchange membrane production from natural polymers for the purification of immunoglobulins

Immunoglobulins have become one of the most important products in pharmaceutical biotechnology. Chromatographic separation techniques are widely used in purification steps of immunoglobulins and hence, production cost gets increased. In this project, natural biopolymer bacterial cellulose (BC) is prepared and modified to increase ion exchange capacity to use in purification of immunoglobulin G (IgG) and immunoglobulin A (IgA). Totally, 5 modifications were performed. Hydroxyethyl acrylamide (HEA), epichlorohydrin, ammonium hydroxide (NH3), caffeic acid and propane sultone (SO3) were used for obtaining modified polymers. The membranes chosen to proceed with were, BC, BC-HEA, BC-HEA-NH3, BC-HEA-SO3; based on membrane integrity. Young's modulus values were determined. Fourier's transformation infrared spectroscopy (FT-IR) was used for observing modifications and scanning electron microscopy was used to observe surface and cross-section changes of the membranes. These observations were supported by SEM images. Hydraulic permeability, porosity and pore size of membranes were calculated. Hydraulic permeability values were very high compared to commercial membrane units. There is no protein binding at high hydraulic permeability. The porosity of BC membranes were in the range of 45–95% depending on the modification type. Effective area for protein adsorption was also calculated. Effective area of bacterial cellulose membranes were around 2cm2 and between 2–15cm2 at constant surface area (17.35cm2) respectively. Effective area directly affect adsorption yield. BC membranes were more preferable for adsorption based on physical conditions. Modifications generally increase the ion exchange capacities of membranes. Before starting to purification experiments of IgG and IgA, fetal bovine serum albumin (BSA) was used for protein affinity experiments. Using the data, feasible adsorption theory was selected for membranes. All BC membranes are fitted to Langmuir isotherm. Protein affinity was calculated using BSA, IgG and IgA proteins. BC showed low protein affinity; however, protein binding yield was higher than other membranes. BC membrane was the best for protein affinity, even it has low ion exchange capacity. BC membranes will be used to purify proteins in following studies.