Effect of salt: Protein solubility increases slightly (“salting-in”) at
low salt concentrations and decreases (“salting out”) at high salt
concentrations. Salt-induced precipitation of proteins is a widely
used method for product recovery of biomolecules.
The proteins used in this work were insulin (bovine), lysozyme
(hen), and albumin (bovine). The effect of agitation on attainment
of equilibrium solubility was studied. The effect of degree of
supersaturation on solubility results was assessed. Solubility
results obtained by titration were compared with those obtained by
dialysis, which is a more conventional method for determining
protein solubility. Finally, the utility of salt titrations in selectively
precipitating a protein from a mixture of proteins was assessed.