Esterification‐coupled extraction of organic acids: Partition enhancement and underlying reaction and distribution equilibria

A novel means of extracting carboxylic acids from aqueous solutions is described which involves the use of a lipolytic enzyme to convert the acid to a more hydrophobic ester. A water‐immiscible long‐chain alcohol serves both as a reactant in esterifying the acid, and as a solvent for extraction of the ester. Radiochemical tracer studies of the underlying reaction and extraction equilibria established that a low equilibrium concentration of ester (0.04–0.5m M ) in the presence of water is counterbalanced by the high distribution coefficient of the ester (220–3380, wt. basis). The net result is a substantial (4‐ to 15‐fold) increase in the apparent distribution coefficient of the acid; 80%–95% of the extracted acid is in the esterified form. The method is applicable to a variety of alcohols and acids.