Enzymatic synthesis of carbohydrate esters in 2-pyrrolidone

Abstract

The lipase-mediated esterification of sorbitol and fatty acid was investigated in a two-phase system with 2-pyrrolidone as cosolvent for sorbitol. The lipase from Chromobacterium viscosum showed an initial esterification rate of 1.4 mmol g −1h −1, and after 74 h, 80% of the initial sorbitol content was converted into sorbitol esters. With fructose or glucose as a substrate, initial esterification rates were 0.2 and 0.04 mmol g −1h −1, respectively; disaccharides were not reactive at all. The effects of the sorbitol, fatty acid, water, and 2-pyrrolidone concentrations on esterification activity were studied. An excess of fatty acid and a water concentration around 1 m were found to be necessary for optimum ester production. The polar organic cosolvent 2-pyrrolidone can inactivate the lipase. It is a suitable cosolvent for carbohydrates, provided that its concentration is low. Esterification was also studied in a two-phase membrane reactor. The value of the enzyme-based initial reaction rate was half of the reaction rate in an emulsion system. The water activity in the membrane system was relatively high, which resulted in low product yields.