Process of high purity albumin production
A process is provided for the preparation of albumin which has extremely low levels of or is essentially free of colorants, metal ions, human proteins, host proteins, fragments of albumin, polymers or aggregates of albumin and viruses, and which is essentially non-glycated, relatively high in free thiol and with an intact C-terminus. The process comprises passing albumin (preferably expressed and secreted by transformed yeast) through positive mode cation exchange and then positive mode anion exchange chromatography. Other steps may also be employed, ultrafiltration, gel permeation chromatography, affinity chromatography binding the albumin by using blue dyes) and affinity chromatography binding contaminants by using an aminophenylboronic acid resin. Elution of albumin, with a compound having affinity for albumin, from a material having no specific affinity for albumin is also disclosed, as is removal of ammonium ions with a counter-ion.
1. A process for purifying albumin from a yeast culture medium obtained by culturing yeast transformed with an albumin-encoding nucleotide sequence in a fermentation medium, whereby said yeast expresses and secretes albumin, the process comprising the steps of:
(a) separating the yeast from the culture medium to yield an albumin solution;
(b) conditioning the albumin solution from step (a) by adding octanoate to a final concentration of from about 1 to about 10 mM and adjusting the pH so that it is from about 4.0 to about 5.0;
(c) subjecting the albumin solution from step (b) to cationic exchange chromatography in which the albumin is bound to a cation exchange material and eluting the bound albumin from the material by applying a solution of a compound having a specific affinity for albumin;
(d) subjecting the albumin eluted from the cation exchange material without any intervening treatment or without any intervening treatment other than dilution to anion exchange chromatography in which the albumin is bound to an anion exchange material and the albumin is eluted from the anion exchanger with a buffer containing from about 50 to about 200 mM boric acid salt;
(e) ultrafiltering the albumin-containing solution obtained thereby through an ultrafiltration membrane to obtain an ultrafiltration retentate having an albumin concentration of at least about 80 grams of albumin per liter and diafiltrating the ultrafiltration retentate against at least five retentate equivalents of a salt solution;
(f) sterilizing the albumin containing retentate resulting from the diafiltration of step (e) by sterile filtration; and
(g) filling a formulation vessel with the sterile filtered albumin product of step (f).
2. A process according to claim 1 wherein the compound having a specific affinity for albumin is a faffy acid salt.