Enzymatic Synthesis of Esters of Polyethylene Glycol-400

Abstract

Esters of fatty acids (FA) and polyethylene glycol-400 (PEG) are valuable surface-active compounds usually produced by chemical methods. This study shows the possibility of replacing the chemical synthesis of polyethylene glycol esters by the enzymatic synthesis, which is implemented under milder conditions and via a simpler and more environmentally friendly technology. The main obstacles for the enzymatic synthesis of PEG and higher fatty acids are the high viscosity of PEG and a low solubility of FA in water. These problems were solved by the selection of an organic solvent and by the choice of other conditions of the process carried out by pancreatic lipase. The optimal conditions for the synthesis of esters of PEG and FA were determined as follows: the reaction medium was benzene/hexane in the ratio of 2/3; a temperature was 25 °C; the water content was not above 0,2 %; the molar ratio of FA/PEG was equal 1/1,8; and the reaction time was 48 h. The product yield under these conditions was: 80 % for the synthesis of PEG ester and capric acid, 78 % for the synthesis of PEG ester and lauric acid, and 44 % for the synthesis of PEG ester and palmitic acid.