Preparation and Characterization of Macroporous Carrageenan Beads for Enhanced Gel Filtration

Abstract

Macroporous K-carrageenan beads were prepared by two–step emulsion method, chemically cross-linked characterized, and then employed for gel filtration. It has recently been recognized that convection (i.e. bulk fluid movement) through large pores (i.e. macropores ) is an effective way of enhancing the performance of chromatographic separation by improving mass transfer. The aim of our study was to determine if this concept was true for macroporous and carrageenan beads. The pore structure of the beads was analyzed by environmental scanning electronic microscopy and characterized by measuring the total surface area and packing density. An increasing toluene content in the first emulsion was found to play an important role in creating more pores and in determining the pore structure. In addition, heat treatment of the beads was very effective for increasing the cross linking density and reducing the bead volume swelling in saline. However, treatment with steam reduced the bead surface area suggesting a change in pore structure. The cross linked hydrogel beads were stable in the pH range 1-13 and in KCI solutions at a concentration over 0.07 M. The bead size increased with a decrease in ionic strength. At low ionic strength, two of the proteins studied, cytochrome C and lysozyme, were found to adsorb to the carrageenan beads. The ionic stength also affected the fractionation range of the beads for gel filtration. The elution volume of various non-adsorbed proteins was reduced with a decrease in ionic stength. The efficiency (i.e. resolution and reduced plate heights) of carrageenanbeads in chromatographic separation was better than that of commercial Sepharose CL-6B beads , especially at high flow rates.