Zinc ion-promoted adsorption of lysozyme to Cibacron Blue F3GA-attached microporous polyamide hollow-fiber membranes

Abstract

Dye-affinity and metal chelate affinity adsorption are increasingly used for protein separation. Synthetic hollow fiber membranes have advantages as support matrices in comparison to conventional bead supports because they are not compressible and they eliminate internal diffusion limitations. The goal of this study was to explore in detail the performance of hollow fibers composed of modified polyamide to which Cibacron Blue F3GA and Zn(II) were attached for adsorption of lysozyme. The polymer matrix was characterized by scanning electron microscopy. These dye-affinity and Zn(II) chelated hollow-fibers were used in the lysozyme adsorption-elution studies. The effects of initial concentration of lysozyme and medium pH on the adsorption efficiency of dye-attached and metal-chelated hollow-fibers were studied in a batch reactor. The effect of Zn(II) loading on lysozyme adsorption was also studied. The non-specific adsorption of lysozyme on the polyamide hollow-fibers was 1.8 mg g(-1). Cibacron Blue F3GA attachment significantly increased the lysozyme adsorption up to 63.2 mg g(-1). Lysozyme adsorption capacity of the Zn(II) chelated hollow-fibers (144.2 mg g(-1)) was greater than that of the Cibacron Blue F3GA-attached hollow-fibers. A significant amount of the adsorbed lysozyme (up to 97%) was eluted in 1 h in the elution medium containing 1.0 M NaSCN at pn 8.0 and 25 mM EDTA at pH 4.9. In order to examine the effects of separation conditions on possible conformational changes of lysozyme structure, fluorescence spectrophotometry was employed. We conclude that dye- and metal-chelate affinity chromatography with polyamide hollow-fibers can be applied for lysozyme adsorption without causing any significant conformational changes and denaturation. Repeated adsorption/elution processes showed that these novel dye-attached and Zn(II) chelated hollow-fibers are suitable for lysozyme adsorption