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 (0.04-0.5mM) 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.
Aires-Barros
M R
MR
Laboratorio de Engenharia Bioquimica, Institute Superior Tecnico, 1000 Lisboa, Portugal.
Cabral
J M
JM
Willson
R C
RC
Hamel
J F
JF
Cooney
C L
CL