Synthesis of mono- and diglycerides in water-in-oil microemulsions

Enzyme-catalyzed esterification was carried out in single-phase, oil-continuous microemulsions. The lipozyme was solubilized, along with glycerol and water, in the aqueous core of water/diethylhexyl sodium sulfosuccinate/hydrocarbon microemulsion system. Upon addition of fatty acid, mono- and diglycerides were formed, due to the esterification reaction taking place at the interface of the droplets in the microemulsion. The initial rate of conversion of oleic acid increases with oil chainlength of the continuous phase whereas final conversion is maximum for hexane. The conversion of stearic acid is 30% whereas conversion of oleic acid is 70%. The percent conversion of various fatty acids in the same continuous medium increases with fatty acid chainlength. The oleic acid/glycerol ratio is an important parameter for optimum conversion of oleic acid into glycerides. The yield can be increased by subsequent addition of glycerol after equilibrium is reached. High-performance liquid chromatography analysis of samples from microemulsions shows the presence of mono- and diglycerides. Possible mechanisms for the abovementioned effects are discussed.