Question

A water immiscible solvent can be used for liquid-liquid extraction. However, solvents can denature proteins. What is the alternative chemical for liquid-liquid extraction? Very short answer is enough.

Answer 1

The 2 well established systems of liquid-liquid extraction; one is the ATPS utilizing two immiscible aqueous phases of simple electrolytes and water soluble polymers or of two incompatible water soluble polymers, while the other is the reverse micellar extraction (RME) using the water in oil microemulsion .

Using reversed micelle in liquid liquid extraction proteins can be extracted.It has been proven that proteins can be solubilized within these reverse micelles in active form . This method is more suitable for separating proteins than conventional liquid–liquid extraction or other methods that were used in the past because the transfer of proteins into solvents often results in irreversible denaturation and loss of biological activity .The distribution of proteins between the micellar phase and aqueous phase is largely determined by the environments of bulk aqueous phase, i.e., pH, ionic strength and type of salt. Parameters which are related to the organic phase also affect the distribution of protein , such as type and concentration of surfactant, presence of co-surfactant and type of solvent . By controlling parameters via the variations of protein-micelle electrostatic, hydrophobic and steric interactions etc extraction efficiency of proteins can be increased.The water-containing microemulsion droplets can selectively extract protein molecules from water-in some cases removing nearly 100 % of the protein-depending on the pH and salt concentration of the system. Microemulsions are extensively explored for their potential in effecting a liquid-liquid separation of a target protein from other components in the cell broth with potential for continuous purification .

There is an assured correlation between between pH, surfactant charge and extraction yield .Generally speaking a negatively charged surfactant such as AOT extracts favourably a protein with positively charged surface intimating a solution pH below it's pI whereas a cationic surfactant could be utilized at a pH higher than its As the hydrophobicity is increased there is a concomitant increase in ease of extraction .At low phase volume ratio, sufficient surfactant concentration was not available in the reaction mixture to form the required amount of reverse micelles which ultimately results in less protein extraction.