Enzymatic Synthesis of Sugar Fatty Acid Esters

Enzymatic synthesis of sugar fatty acid esters was performed in an organic solvent using an immobilized Candida antartica lipase and various sugars and oleic acid as substrates. A high solubility of the sugar in the solvent was needed for a high sugar ester yield. Among the sugars and solvents tested in this study, the highest yield (98 %) was obtained when xylitol and 2-methyl 2-butanol were used as the sugar and solvent, respectively. The optimal sugar-to-fatty acid ratio was in the range from 2:1 to 3:1 for a high conversion and minimization of the residual fatty acid concentration. The water content in the reaction medium was critical and had to be kept below 0.15 % to obtain a high sugar ester yield. The half life cycle of the enzyme used in this study was observed after 9-repeated uses. In a pilot reaction test, water formed during the reaction was effectively removed by recycling the reaction medium through a molecular sieve column outside the reactor; thus, a high sugar ester yield was obtained.