Methods and Compositions Involving Whey Protein Isolates

Abstract

The present invention concerns methods of isolating milk proteins. Methods of the invention include charged ultrafiltration processes that use variations in pH to further separate protein species.

1 . A method for fractionating a protein mixture comprising multiple protein species to obtain a protein of interest comprising:
 (a) adjusting the pH of said protein mixture based on the isoelectric point of said protein of interest, thereby rendering a net charge of about zero on said protein of interest,   (b) adjusting the conductivity of said protein mixture such that said multiple species other than said protein of interest are rejected by a charged ultrafiltration membrane; and   (c) contacting said mixture with said charged ultrafiltration membrane to achieve a first permeate and a first retentate, wherein said ultrafiltration membrane has a pore size at least 100 kDa above, or 10× greater than, at least one of said multiple species other than said protein of interest,   wherein said first permeate comprises an increased ratio of said protein of interest as compared to said protein mixture.   
     
     
         2 . The method of  claim 1 , wherein said protein mixture is a milk protein or a whey protein mixture. 
     
     
         3 . The method of  claim 1 , wherein said charged ultrafiltration membrane has a pore size rating of 150-500 kDa. 
     
     
         4 . The method of  claim 3 , wherein said charged ultrafiltration is affected by a ultrafiltration membrane having a pore size rating of about 300 kDa. 
     
     
         5 . The method of  claim 1 , wherein said protein mixture comprises one or more of glycomacropeptide (GMP), alpha-lactalbumin (ALA), immunoglobulin G (IgG), and/or beta-lactoglobulin (BLG). 
     
     
         6 . The method of  claim 1 , wherein said method further comprises subjecting said first permeate to a second charged ultrafiltration to achieve a second permeate and a second retentate. 
     
     
         7 . The method of  claim 1 , wherein said method further comprises subjecting said first retentate to a second charged ultrafiltration to achieve a second retentate and a second permeate. 
     
     
         8 . The method of  claim 6 , wherein said second retentate is recycled into another protein mixture for additional charged ultrafiltration. 
     
     
         9 . The method of  claim 7 , wherein said second permeate is recycled into another protein mixture for additional charged ultrafiltration. 
     
     
         10 . The method of  claim 1 , wherein said ultrafiltration achieves a purity of about 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% and 99%. 
     
     
         11 . The method of  claim 6 , wherein said ultrafiltration achieves a purity of about 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% and 99%. 
     
     
         12 . The method of  claim 7 , wherein said ultrafiltration achieves a purity of about 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% and 99%. 
     
     
         13 . The method of  claim 1 , wherein said ultrafiltration achieves a yield of about 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% and 99%. 
     
     
         14 . The method of  claim 6 , wherein said ultrafiltration achieves a yield of about 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% and 99%. 
     
     
         15 . The method of  claim 7 , wherein said ultrafiltration achieves a yield of about 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% and 99%. 
     
     
         16 . The method of  claim 3 , wherein said ultrafiltration membrane is positively-charged. 
     
     
         17 . The method of  claim 3 , wherein said ultrafiltration membrane is negatively-charged. 
     
     
         18 . The method of  claim 1 , wherein said conductivity is adjusted to 3-10 mS/cm. 
     
     
         19 . The method of  claim 1 , wherein said conductivity is adjusted to 3-6 mS/cm. 
     
     
         20 . The method of  claim 1 , wherein GMP is separated from ALA. 
     
     
         21 . The method of  claim 1 , wherein GMP is separated from IgG. 
     
     
         22 . The method of  claim 1 , wherein GMP is separated from BLG. 
     
     
         23 . The method of  claim 1 , wherein ALA is separated from IgG. 
     
     
         24 . The method of  claim 1 , wherein ALA is separated from BLG. 
     
     
         25 . The method of  claim 1 , wherein BLG is separated from IgG. 
     
     
         26 . The method of  claim 1 , wherein said charged ultrafiltration is effected by a multistage cross-flow positively-charged of ultrafiltration membrane.