Membrane adsorbers (MAs) are used for protein separation in controlled
mixed-mode interaction chromatography. The strong anion- and cation-e
xchange MAs used are made either from a synthetic copolymer or from mo
dified cellulose membranes. The affinity MAs (Cibacron Blue) are also
made from the copolymer membranes. Standard protein mixtures, whey pro
teins, and biotechnological culture supernatants are separated. The in
fluence of the flow-rate, the ratio of cation- and anion-exchange MAs
inserted in the stack, and the pattern, i.e. the comparative worth of
an alternating vs. a two-consecutive-stacks arrangement, on the separa
tion is investigated. While the flow-rate shows no influence, both the
pattern of arrangement and the ratio of the two types of ion exchange
r do. Compared to single-mode MA chromatography, a broader range of pr
oteins, e.g. in terms of the isoelectric points, can be separated in a
single chromatographic procedure, Whey proteins (beta-lactoglobulin,
alpha-lactalbumin, BSA, IgG) are separated at pH 6, using a mixed-mode
ion-exchange system. Here however, a two-stack approach is used to al
low for module-uncoupling before elution, to prevent IgG and cy-lactal
bumin from coeluting. By using a mix of anion-exchange and Cibacron Bl
ue affinity MAs, recombinant human antithrombin III (rh-AT III) can be
separated in a single run from the major protein impurities present i
n the fermenter supernatant, namely transferin and BSA.