Ammonium Sulfate precipitation

Aim

To precipitate out dissolved egg white protein by ammonium sulfate precipitation

salting out

Principle

Salts such as ammonium sulphate and sodium sulphate ae used for the recovery and fractionation of proteins. As the salt concentration of a solution increases, more of the bulk water become associated with salt ions. The salts remove water from the surface of the protein revealing hydrophobic patches which come together causing the proteins to precipitate. Proteins which exhibit hydrophobic interactions aggregate and precipitate from the solution, which is also called salting out. This is a vital step in downstream processing of proteins. Precipitation relies on the principle that when compounds of higher affinity are added to the protein solution in a solvent, the protein get separated as a precipitate.

 Materials Required

Egg white solution, 20% ammonium sulphate solution, glass rod, routine microbiological facilities

Procedure

1. 20 % ammonium sulphate solution was gently added to the solution of egg white with constant stirring, till precipitation was maximum.

2. The mixture was filtered and washed with ammonium sulphate solution in a funnel over filter paper

Result

The egg white protein was precipitated.