Enzymatic synthesis of mono-, or diacylglycerol in organic solvent

Abstract

In order to produce mono-, or diacylglycerols, the lipase-catalyzed synthesis of palmitic glycerids was performed with n-hexane as a model reaction system. Quantitative analysis of the reaction mixture was conducted by using gas chromatography (GC), which enabled the compositional analysis of fats and oils as well as monitoring lipase reaction. In this reaction system, lipase-catalyzed esterification was conducted in two phase system which was composed of hydrophilic glycerol and water-immiscible organic media. Therefore, increasing the interfacial area between the two phases was essential for effective esterification. For the purpose of increasing the interfacial area, various inert solid powders were added to the reaction system. Among the tested solid powders, silica gel was the most suitable for increasing the interfacial area. In order to accumulate mono-, or diacylglycerols in this reaction system, the difference of solubility in organic solvent of reaction products and specificity of various lipase sources were used. It was found that as soon as the target product was formed, the product was quickly precipitated, and accumulated in the reactor. The solubility of each reaction products was greatly influenced by reaction temperature, and optimum reaction temperature was appeared at $25\,^\circ\!C$. In this reaction condition, Lipozyme showed its specificity to produce dipalmitin, but lipase from Rhizopus delemar showed its specificity for producing monopalmitin. Optimal molar ratio of glycerol to palmitate was observed at 5:10. For the purpose of increasing the purity of reaction product, 90 wt\% of mono-, or dipalmitin were obtained through the simple purification steps.