Extractive Synthesis of Ethyl-Oleate Using Alginate Gel Co-Entrapped Yeast Cells and Lipase Enzyme

To synthesize ethyl‐oleate ester, a complex Ca‐alginate gel co‐entrapped system was prepared. The gel beads contained two kinds of biocatalysts (living yeast cells and a lipase enzyme) and various amounts of glucose (100–400 g/L). These alginate beads dispersed directly in pure oleic acid. To follow the bioconversion of the cell growth, the glucose uptake of yeast cells, the concentration of ethanol inside the gel beads and the ethyl‐oleate concentration in oleic acid phase was monitored. The glucose was quantitatively taken up by yeast cells during 24–72 h, depending on the concentration of glucose. After this 24–72‐hour period, the glucose uptake was stopped. In accordance with changes in glucose concentration, the concentration of ethanol and ethyl‐oleate increased rapidly during the first day of fermentation and thereafter slowed down. It is supposed that the inhibitory effect of produced ethanol would be resolved by co‐immobilization of lipase in the same gel particles. Using lipase, one is able to transform ethanol to ethyl‐oleate, which is soluble in oleic acid. According to the data obtained a minimum of 4 U/mL lipase is required to increase ethyl‐oleate production significantly. Summing up it can be concluded that by means of this system a maximum yield of ethanol and ethyl‐oleate was achieved when gel beads containing 100 g/L glucose and 4 U/mL lipase enzyme were used. The bioflavors are an important group within natural food additives. The production of flavor ester via extraction from plants is subject to various problems, and, therefore, the biocatalytic way of production becomes more and more important. Natural ethyl esters can be formed by enzymatic esterification of ethanol produced from glucose by yeasts. In this paper an enzymatic and a microbiological process both applying the same immobilized microorganism are combined. Such an approach could also have innovative potential for the production of fatty acid ethyl‐esters.