Studies on the enzymatic synthesis of sugar esters in organic medium and supercritical carbon dioxide

The acylation of glucose and fructose by various fatty acids catalyzed by Rhizomucor miehei lipase in n-hexane and supercritical carbon dioxide was studied. The solvent-immiscible sugars were introduced in the reaction mixture adsorbed onto a solid support of silica gel or cellulose. The reaction parameters affecting the yield and the regioselectivity of the reaction such as the nature and the concentration of fatty acids as well as the water activity (a(w)) of the system were investigated. Typically, yields of about 50-60 % were obtained in both systems used when silica gel was used as solid support at a(w) = 0.48. However, at the same initial water activity (a(w) = 0.48), 10-15 % lower yields were obtained for the reaction with cellulose as a solid support. Sugar monoesters are the dominant products, but significant amount of sugar di- and triesters were also produced depending on the molar ratio of fatty acid to sugar used.