For purification of antibodies from Milk see Purification of antibodies

Separation of Casein from Whey (for separation of specific proteins in Whey see outline)

The supernantant fluid generated during cheese manufacturing is commonly referred to as whey. Proteins contained in whey, which are soluble proteins including lactoferrin, lactoperoxidase, immunoglobulins, albumin, alpha-lactalbumin and beta-lactoglobulin are referred to as “whey proteins”. Whey has long been the predominant source of milk proteins and significant effecrts have been devloted to separation and isolation of various whey proteins.

Although whey is discarded during cheesemaking (the “curd” which is formed when milk is acidified (becomes sour) is used to make cheese) it has significant value as a source of nutrition. It is used in andies and special cheese products. In addition large quantities of dry and concentrated forms are mixed with food and feeds.

The separation of Casein from Whey involves separation of casein, an insoluble protein contained in whole milk, from other components by precipitation. The two predominant precipitation techniques are rennet precipitation and acid precipitation, which are ulternatively utilized, depending on the specific type of cheese to be produced. 

Rennet precipitation (Sweet Whey): is produced when the caseins are enzymatically coagulated using rennet type enzymes at a pH of 5.9 to 6.3. rennin is added to warm milke caseins which are precipitated leaving the whey proteins in solution. Whey produced by this method is referred to as “sweet whey”. By far of the whey produced as a cheese manufacturing by product, nearly all of it was sweet whey. (Gerberding, J. Chromatography A 808 (1998) 141-151)

Acid precipitaiton (Acid Whey): is carried out at the isoelectric point of milk (i.e., 4.7) through the use of acid to precipitate out casein and leave the whey in solution. Whey produced by this method is referred to as “acid whey”. (US 6096870).

Filtration: 

Multi-filters

Couto (US2004/0167320) teaches a process that employess three filtration unit operations that clarify, concentrate and fractionate a product such as an antibody from a transgenic milk volume contianing the molcule of interest. 

Koph (US 2003/0059512) teaches a method of separation of a casein-rich fraction and a casein-depleted fraction of milk by (a) providing a source of milk, (b) optionally flowing the milk through a cream separator to remove all or at least a portion of the fatty component of the milk, (c) optionally pastuerizing the milk, (d) flowing the milk through a cross-flow filtration module to separate the milk into a casein rich retentate fraction and a casein depleted permeate fraction and (e) recovering both the casen rich fraction and the casein depleted fraction. 

Microfiltration

Milk serium protein can be made by MF of milt to remove the caseins. Etzel (WO 2012/012237)

Charged Ultrafiltration

–AEX Membranes (positively charged membranes):

Etzel (WO 2012/012237) discloses a method for fractionating a protein mixture that includes multiple protein species such as milk by (a) adjusting the pH of the mixture to an isoelectric point just below the pI of the protein of interest, thereby rendering a net charge of about zero on the protein of interest and also adjusting the conductivity of the mixture such that shielding of the multiple species other than the protein of itnerest is limited to the extent that the other species are rejected by the charged UF. The charged UF may have a pore size rating 150-500kDa and the protein of interest includes glycomacropeptide (GMP*, alpha-lactalbumin (ALA), IgG and/or beta-lactoglobulin (BLG). For example, milk serum proteins can be made by MF of milk to remove the caseins. Alpha-lactalbumin is smaller and more acidic  (14.4 kDa; pI 4.4) than beta-lactoglobulin (18.67 kDa pI 5.1). By adjusting the milk serum protein to about pH 4.0-4.5, the alpha lactalbumin has little to no net charge while the beta lactoglobulin has a net positive charge. The alrge beta lactoglobulin will be subject to electrostatic repulsion by a positivley charged UF while the smaller alpha-lactalbumin that has little to no net charge can permeat the charged UF. Howev, increasing the conducitvity of the protein mixture increases shielding of the charges on the proteins. As conductivity increases to above about 100 mS/cm, charge shielding is great enough to negate the effect of electrostatic repulsion. Thus there is a blance between pH and conductivity.