Production of flavour esters by immobilized Staphylococcus simulans lipase in a solvent-free system

Ethyl valerate (green apple flavour) and hexyl acetate (pear flavour) are short-chain esters with fruity notes that are widely used in food, cosmetic and pharmaceutical industries. Crude Staphylococcus simulans lipase was immobilized on different supports. The CaCO 3 was selected as the most suitable support offering maximum adsorption capacity. Different reaction parameters for enhancing ester formation were investigated. In fact, higher conversion of ethyl valerate (51%) was achieved by the addition of 20% (w/w) of water to the reaction mixture, using 200 IU of immobilized lipase, a molar ratio valeric acid to ethanol of 1 and at 37 °C. No decrease of the synthesis activity was observed for 10 cycles of use of the immobilized lipase. In the case of the hexyl acetate, the optimum conditions, giving 41% of conversion, are obtained with 10% (w/w) of initially added water, 100 IU of immobilized lipase, a molar ratio acetic acid to hexanol of 1 and at 37 °C. Immobilized lipase could be repeatedly used for five cycles without a decrease of synthesis activity.