Effect of salt hydrate pairs for water activity control on lipase-catalyzed synthesis of lysophospholipids in a solvent-free system

Abstract

For the synthesis of biologically useful lysophospholipids with a desirable fatty acid, an easy and simple synthetic approach was developed by lipase-catalyzed esterification of the glycerophosphoryl group with free fatty acid in a solvent-free system. Among the various parameters which govern the lysophospholipid synthesis, water activity (a w) was found to be an important factor. Salt hydrate pairs could act to buffer the optimal water level during the reaction. We investigated the effect of various salt hydrate pairs which were added directly into the reaction medium or put in the headspace of the reactor on the lysophospholipid synthesis in the solvent-free system. Optimal a w values for lysophosphatidic acid (LPA), lysophosphatidylethanolamine (LPE), and lysophosphatidylcholine (LPC) were 0.18, 0.37, and 0.60, respectively, and these were controlled by the pairs of NaI (2 H 2O-anhydrous), CH 3COONa (3 H 2O-anhydrous), Na 4P 2O 7 (10 H 2O-anhydrous), respectively. Control of a w was especially critical for LPE synthesis. When the a w of the reaction system was not controlled, LPE was hardly formed. The yield of LPA, LPE, and LPC at their optimal a w values after 60 h were 45.3, 22.9, and 36.2%, respectively.