Biosynthesis Coupled to the Extraction of Geranyl Acetate in a Liquid-Gas System: Optimization of the Transesterification Reaction and Modeling of the Transfer

The objective of this paper was to study the production and the mass transfer of geranyl acetate known for its interesting green odor properties. Lipase-catalyzed geranyl acetate production via transesterification reaction with ethyl acetate in organic solvent was investigated. The production was catalyzed by using immobilized lipase from Rhizomucor miehei, and the recovery was achieved by using solid phase microextraction (SPME) fiber system (50/30 μm DVB/Carboxen/PDMS Coating). The effects of different reaction parameters on transesterification including the enzyme concentration, the substrate molar ratio, the added water, and the reaction time were firstly optimized. A higher yield of 82 % was achieved under near-anhydrous conditions at 55 °C by using an enzyme concentration of 6 % (w/w reactants), a molar ratio of geraniol to ethyl acetate of 1:5, and a reaction time of 6 h. Immobilized lipase was repeatedly used for four cycles with no decrease in reaction yield. The mass transfer of geranyl acetate from the organic to gas phase was studied theoretically and experimentally, and a transfer yield of 52.3 % was obtained. The simulation showed that the Fuller-Schettler-Giddings model exhibited good correlation with the experimental data

Voie de la lipoxygénase : valorisation d’huiles végétales et biosynthèse de flaveurs

Lipoxygenase pathway: valorization of plant oils and aroma biosynthesis. This article is a review on the lipoxygenase pathway in plants, and its application in aroma compound synthesis from plant oils. Raw material used by this pathway is plant oils rich in poly-unsaturated fatty acids. Then, lipase-catalyzed hydrolysis followed by lipoxygenation, hydroperoxyde-lyase and alcohol-dehydrogenase act successively producing respectively aldehyde and alcohol. Several papers and patents described the production of aroma as hexenal(s), nonenal(s) and nonadienal(s) as well as their corresponding alcohols using enzymes of this pathway from different sources. The reaction sequence uses enzymatic systems of different characteristics, as well as raw material and intermediary and final products having specific properties. In order to improve the efficiency of the application of the lipoxygenase pathway, different studies used multi-enzymatic systems in compartimentalized media for the bioconversion