In this paper the enzymatic manufacture of glycerol monostearate was studied in high polar organic solvents. Water produced during the reaction has a disadvantageous effect on the reaction rate and enzyme activity. This by-product water was removed and the water content was kept constant using a pervaporation unit which could be integrated on-line with the reaction system. The best yield (90%) after 6 h reaction time was achieved at 40 C, at seven-fold glycerol excess using dioxane as solvent. The enzymatic esterification reaction could be described by the Random Bi-Bi mechanism. A mathematical model have been estimated and experimentally verified by a set of experiments with varying and constant water contents. The experiments both in batch and integrated system (esterification-pervaporation) could be described with good accuracy by the proposed model.