Flocculation and characterization of protein by anionic copolymer containing reactive functional groups

Two types of anionic copolymers with reactive functional groups of amido, carboxyl and sulfonate were prepared and used to study the flocculation and characterization of lysozyme in aqueous solution. Initial increase of the ionic strength promotes flocculation, but no flocculation occurs with further increase of ionic strength. High ionic strength in solution also makes the aggregates of protein–copolymer sensitive to shear. The two types of flocculants require high pH to achieve high charge density for interacting with lysozyme effectively. Adsorption of lysozyme to the anionic copolymers was influenced strongly by pH and ionic strength. The results reveal an understanding of the types of zeta (ζ) potential when lysozyme aggregates with copolymers. The performances of the anionic copolymers are related to their compositions when they are used as flocculants. The results confirm the mechanism of charge neutralization that prevails for highly charged polymers.