Synthesis of Flavours using Supercritical Carbon Dioxide

Environmentally friendly synthesis of flavours and fragrances by enzyme catalyzed production processes using supercritical carbon dioxide as process medium A lot of natural flavours and fragrances used in the food and beverage, cosmetic and pharmaceutical industries are fatty acid esters synthesized in plants by enzymes. The conventional extraction out of the plants is often expensive and the products vary in quality. So large-scale production of these esters is normally done by chemical processes requiring purification steps and sometimes involving high temperatures, which leads to decomposition of heat sensitive components. Furthermore these products have to be labeled -artificial- for the market. Lipases, enzymes which normally catalyze hydrolysis of triglycerides in human, animal or microbial metabolism, can be used as biocatalysts in non-aqueous organic solvents to produce flavours (fatty acid esters f. e. terpenyl esters). Because of the biocatalyst the reaction can be performed under mild reaction conditions and the products can be labeled as - natural aroma-. An interesting alternative to organic solvents, which are injurious to health, flammable and expensive, is the non-aqueous solvent supercritical carbon dioxide. This reaction medium is cheap, non toxic, non flammable, has higher diffusivities than conventional organic solvents and permits a facilitated, energy saving separation process from the product by depressurization. In addition because of its tuneable solvent power the supercritical carbon dioxide can be used also for downstream processing, which makes an integrated production process possible using only one unique process medium. The goal of the project is to develop and model a complete continuous process for the biocatalytic production of the terpenyl esters geranylbutyrate and geranylcaprylate in supercritical carbon dioxide. This includes following steps: determination of reaction kinetics in batch reactor, determination of phase equilibria, continuous reaction process, continuous separation process, integrated production process and economical evaluation.

A lot of natural flavours and fragrances used in the food and beverage, cosmetic and pharmaceutical industries are fatty acid esters synthesized in plants by enzymes. The conventional extraction out of the plants is often expensive and the products vary in quality. So large-scale production of these esters is normally done by chemical processes requiring purification steps and sometimes involving high temperatures, which lead to decomposition of heat sensitive components. Furthermore these products have to be labeled "artificial" for the market. Lipases, enzymes which normally catalyze hydrolysis of triglycerides in human, animal or microbial metabolism, can be used as biocatalysts in non-aqueous organic solvents to produce flavours (fatty acid esters like terpenyl esters). Because of the biocatalyst the reaction can be performed under mild reaction conditions and the products can be labeled as "natural aroma". An interesting alternative to organic solvents, which are injurious to health, flammable and expensive, is the non- aqueous solvent supercritical carbon dioxide (SC-CO 2 ). This reaction medium is cheap, non toxic, non flammable, has higher diffusivities than conventional organic solvents and permits a facilitated, energy saving separation process from the product by depressurization. In addition because of its tuneable solvent power the supercritical carbon dioxide can be used also for downstream processing, which makes an integrated production process possible using only one unique process medium. The goal of the project was to develop a complete continuous process for the biocatalytic production of a terpenyl ester in supercritical carbon dioxide. This had been performed for geranyl butyrate including following steps: determination of reaction kinetics in batch reactor, determination of phase equilibria, continuous reaction process, continuous separation process, integrated production process and economical evaluation.