Solubility of amino acids, sugars, and proteins*

The importance of biomolecules is well recognized nowadays, owing to their application in many industrial processes, particularly in the food, pharmaceutical, and cosmetic industries. Amino acids, carbohydrates, and proteins are the three types of biomolecules considered in this review. Solubilities of several amino acids and sugars have been measured in water and, more recently, in mixed solvents, both with or without salts. Experimental data on partition of proteins in aqueous two-phase systems (ATPSs), with polymers or salts, have also been reported in the literature. The experimental techniques used are briefly discussed. Regarding modeling, the complexity of these solutions is very high. Sugars form strong hydrogen bonds with one another and with water or other solvents like alcohols. Liquid solutions with amino acids or proteins present not only short-range interaction forces, but also long-range forces, owing to the appearance of charged species. The capabilities of different molecular models and group-contribution-based methods are shown.