An intrinsically shielded hydrogel for the adsorptive recovery of lysozyme

The present paper addresses the selective recovery of lysozyme from egg white using CM-dextran (carboxymethyldextran)-based hydrogels contg. Cibacron Blue as an affinity ligand and co-immobilized BSA intended to act as a shielding agent to reduce non-specific adsorption. Initial studies using pure lysozyme were conducted that indicated that the adsorption capacity increased with ligand d. and that adsorption was well described by a Langmuir-type isotherm. The inclusion of BSA as a putative shielding agent did not decrease the adsorption capacity for lysozyme in single-adsorbate expts. To assess the effectiveness of the shielding strategy, subsequent expts. were conducted with both defined lysozyme/ovalbumin mixts. and hen's-egg white. From these studies, the optimal operating conditions for lysozyme recovery have been detd. These include: optimal initial egg-white concn. [a 10% (vol./vol.) soln. of native egg white in the chosen buffer], affinity-ligand d. (1.86 mM) and ligand-to-shielding-agent ratio (4:1). The purity of lysozyme obtained from egg white was improved from 69% with a non-shielded hydrogel to 94% with an intrinsically shielded hydrogel. Finally, the possibility of using a protein, rather than dextran-backbone-based, hydrogel was investigated. It was found that BSA could take the place of CM-dextran as the gel backbone in a simplified synthesis, producing a gel which also proved effective for lysozyme recovery with a 30% lysozyme in egg-white soln. purified to approx. 92% in a single adsorption-desorption cycle. [on SciFinder (R)]