Abstract: The occurrence of salting out is caused by the decrease of salt concentration to a certain value, which leads to the decrease of water activity, resulting in the surface charge of protein molecules being gradually neutralized, and the hydrated membrane being gradually destroyed, causing protein molecules to aggregate and precipitate from solution. Finally, the precipitate and the supernatant were obtained after separation by a centrifuge.
First, the principle of protein salting out separation:
The solubility of protein in a dilute salt solution increases with the increase of salt concentration (salt solution). When the salt concentration increases to a certain value, the solubility gradually decreases until the protein precipitates. The salting out occurs because the water concentration decreases when the salt concentration increases to a certain value, which causes the surface charge of the protein molecule to be gradually neutralized, and the hydrated film is gradually destroyed, causing the protein molecules to aggregate and precipitate from the solution. The precipitate and the supernatant were obtained after separation by a centrifuge.
Second, factors affecting protein salting out separation:
1. Protein concentration:
The protein concentration is too large, and the co-sinking phenomenon occurs during salting out, and the separation effect is not good. The protein concentration is too dilute, the salt consumption is too large, and the protein recovery rate is low. Generally, the protein concentration is moderate from 2.5% to 3.0%.
2. Ionic strength:
The greater the ionic strength, the lower the solubility of the protein, and the more likely the salting phenomenon occurs.
3. Ion type:
Ions with small ionic radii and high valence have a strong influence on salting out. Ions with large ionic radii and low valence have weaker effects on salting out.
4, PH value:
The more net charge the protein carries, the greater the solubility. When the net charge is zero, the solubility is the lowest. Generally, the pH is adjusted to the vicinity of the isoelectric point of the protein, which is advantageous for salting out.
5, temperature:
Low ionic strength or water, within a certain range of protein solubility increases with increasing temperature. In high-salt solutions, the solubility of proteins sometimes decreases with increasing temperature. Under normal circumstances, operate at 0 to 4 °C.
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