Process of high purity albumin production

Abstract

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, for example ultrafiltration, gel permeation chromatography, affinity chromatography binding the albumin (for example using blue dyes) and affinity chromatography binding contaminants (for example 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, the process comprising the steps of applying a relatively impure albumin solution to a chromatographic material for which the albumin has no specific affinity such that albumin binds to the material, and eluting the bound albumin from the material by applying a solution of a compound having a specific affinity for albumin.  
     
     
         2 . A process according to  claim 1  in which the chromatographic material is a cation exchanger resin.  
     
     
         3 . A process according to  claim 2  wherein the compound is a fatty acid salt such as octanoate.  
     
     
         4 . A process for purifying albumin according to  claim 2 , the process further comprising anion exchange chromatography in which the albumin is bound to an anion exchange material.  
     
     
         5 . A process according to  claim 4  in which albumin eluted from the cation exchange material is subsequently treated by one or more of affinity chromatography, ultrafiltration and gel permeation before being subjected to the said anion exchange chromatography.  
     
     
         6 . A process according to  claim 4  in which albumin eluted from the cation exchange material is applied to the said anion exchange material without any intervening treatment other than dilution.  
     
     
         7 . A process for purifying albumin according to  claim 1 , comprising the steps of: 
 (a) passing an albumin solution through a cation exchange matrix under conditions such that the albumin will bind to the matrix;    (b) eluting from said matrix an albumin-containing cation exchange eluate;    (c) passing said eluate through an affinity matrix comprising an albumin-binding compound;    (d) eluting from said matrix an albumin-containing affinity matrix eluate;    (e) passing said eluate through a gel permeation matrix to obtain a fraction enriched in albumin;    (f) passing said albumin-enriched fraction through an anion exchange matrix under conditions such that albumin will bind to the matrix; and    (g) eluting from said anion exchange matrix a purified albumin-containing product.    
     
     
         8 . A process for purifying albumin according to  claim 1 , comprising the steps of: 
 (a) passing an albumin solution through a cation exchange matrix under conditions such that the albumin will bind to the matrix;    (b) eluting from the matrix an albumin-containing cation exchange eluate;    (c) passing the cation exchange eluate through an anion exchange matrix under conditions such that the albumin will bind to the matrix;    (d) eluting from the anion exchange matrix an albumin-containing anion exchange eluate;    (e) passing the anion exchange eluate through an affinity matrix comprising an albumin-binding compound;    (f) eluting from the affinity matrix an albumin-containing affinity matrix eluate;    (g) passing the affinity matrix eluate through a gel permeation matrix to obtain a fraction enriched in albumin.    
     
     
         9 . A process according to  claim 6  wherein the albumin is eluted in the cation exchange step using a buffer containing a compound having a specific affinity for albumin.  
     
     
         10 . A process according to  claim 9  wherein the compound is an octanoate salt.  
     
     
         11 . A process according to  claim 9  wherein the albumin in the cation exchange step is washed with a high salt solution before being eluted.  
     
     
         12 . A process according to  claim 4  wherein the albumin is eluted from the anion exchanger with a buffer containing 50-200 mM boric acid salt.  
     
     
         13 . A process according to  claim 1  wherein albumin obtained thereby is then, with or without intervening process steps, subjected to chromatography on a resin containing an immobilized compound which will selectively bind glycoconjugates and saccharides.  
     
     
         14 . A process according to  claim 13  wherein the compound is aminophenylboronic acid (PBA).  
     
     
         15 . A process according to  claim 5  wherein the affinity chromatography uses a resin comprising an immobilized albumin-specific dye.  
     
     
         16 . A process according to  claim 15  wherein the dye is a Cibacron Blue type of dye.  
     
     
         17 . A process according to  claim 16  wherein the dye is immobilised on the resin via a spacer.  
     
     
         18 . A process according to  claim 17  wherein the spacer is an α,ω-diamino-(C 1-6 -straight chain alkyl) group.  
     
     
         19 . A process according to  claim 2  wherein, prior to the cation exchange step, the albumin solution is conditioned by adding octanoate thereto to a final concentration of from about 1-10 mM and adjusting the pH to about 4.0-5.0.  
     
     
         20 . A process according to  claim 1  wherein the final albumin-containing solution obtained thereby is then ultrafiltered through an ultrafiltration membrane to obtain an ultrafiltration retentate having an albumin concentration of at least about 80 g albumin per litre and the ultrafiltration retentate is diafiltered against at least 5 retentate equivalents of water.  
     
     
         21 . A process according to  claim 1  wherein the initial albumin solution is 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.