Aqueous media, thermodynamic behavior

Over the last twenty years, biocatalysis in organic solvents has emerged as an important area of research and has led to the widespread industrial use of enzymes. In an aqueous medium, with which enzymes are naturally associated, most substrates are poorly soluble, and this leads to low reaction rates and high reaction volumes. In addition, in water, undesired side reactions and degradation of organic compounds often occur. Also, the thermodynamic equilibrium is unfavorable and product recovery can be difficult. Working in organic solvent avoids these problems, and enzymes often show beneficial behavior in such systems [12-14]. 

In fact this kind of behavior is very general between species of poor entropy of mixing in a common solvent. It was described between attractive polymers in organic medium and between polyanionic polymer and cationic surfactants in aqueous medium. The general shape of the phase diagram can be predicted from thermodynamic calculations but various difficulties, which are discussed, occur to take into account the attractive effects. 

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