Higher antibody binding capacity and lower non-specific protein adsorption enable one-step purification of antibodies from serum samples with purity exceeding 90%. Protein G, a cell wall protein derived from G Streptococci, binds mammalian IgG via its Fc region. The recombinant form of Protein G contains high-affinity binding sites and demonstrates reduced non-specific adsorption. Compared to Protein A, Protein G exhibits distinct IgG binding profiles: it shows stronger binding toward polyclonal antibodies from species such as cattle, sheep, and horses, and effectively binds rat IgG, human IgG3, and mouse IgG1—subtypes that often display weak affinity to Protein A