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A sulfonic group (up to 200 &mgr;mol/mL) membrane was incorporated to epoxy-activated microporous hollow fibers to obtain high-capacity convective ion exchangers. The pure water flux through the membrane decreased exponentially with sulfonic group density and protein binding capacity increased accordingly. At sulfonic group density of 70 &mgr;mol/mL, the membrane lysozyme maximum binding capacity was 84 +/- 9 mg/mL in comparison with its theoretical monolayer maximum binding capacity of 20 mg/mL, thus evidencing tentacle formation. After a cycle of adsorption in a 30 mM sodium phosphate buffer, pH 7. 0, adsorbed lysozyme could be quantitatively recovered following elution with 0.5 M NaCl in the same buffer. Dynamic capacity for lysozyme was 67% of maximum binding, and this value did not change at space velocities ranging from 10 to 40 min-1 as shown by the superimposition of the corresponding breakthrough curves. A cartridge assembled with 21 fibers showed a dynamic-to-static capacity ratio for lysozyme of 0.60 with 1 mg/mL pure lysozyme solution, and 0.42 with a particulate feed composed of 1 mg/mL lysozyme and 0.1 mg/mL yeast.

The worldwide production of whey increases by around 186 million tons each year and it is generally considered as a waste, even when several whey proteins have important economic relevance. For its valorization, inexpensive ligands and integrated chromatography methods need to be developed for specific and low-cost protein purification. Here, we describe a novel affinity process with the dye Yellow HE-4R immobilized on Sepharose for bovine lactoferrin purification. This approach based on a low-cost ligand showed an efficient performance for the recovery and purification of bovine lactoferrin directly from whey, with a yield of 71% and a purification factor of 61.

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An efficient affinity chromatographic matrix based on chitosan for wheat germ agglutinin (WGA) purification was developed. The matrices assayed consisted of chitosan mini-spheres cross-linked with epichlorhydrin 45, 250 or 500 mM. The maximum adsorption capacity of pure WGA - calculated from the corresponding isotherms - was between 43.2 and 48.9 mg/g at pH 5.0 and between 16.6 and 27.6 mg/g at pH 8.5. However, the adsorption of agglutinin from wheat germ extract was higher at pH 8.5. In addition, 0.5 g of mini-spheres cross-linked with epichlorhydrin 250 mM adsorbed 94.5% of the WGA present in 5 mL of the concentrated extract. Acetic acid was able to elute 100% of the adsorbed WGA. The purity of the WGA obtained was greater than 95% and the purification factor was 56.8. The matrix was able to maintain an efficient performance of the purification process for three consecutive cycles. A new method to monitor the purification process by RP-HPLC was developed.