Propriétés de transport de membranes échangeuses d'anions en présence d'ions organiques. Partie II. Influence de la taille de la chaı̂ne aromatique

International audienc

Propriétés de transport de membranes échangeuses d'anions en présence d'ions organiques. Partie I. Influence de la longueur de la chaı̂ne aliphatique

International audienc

Potential use of Cu2+, K+ and Na+ for the destruction of Caulerpa taxifolia: differential effects on photosynthetic parameters

Chemical techniques were investigated in order to eradicate Caulerpa taxifolia, a green alga spreading at a remarkable rate in the Mediterranean Sea. The action of copper, potassium and sodium ions on survival rates and photosynthetic parameters was compared, in order to optimise the conditions of further in situ treatments. The lethal doses were determined and the impact of the studied cations on photosynthesis and respiration rates and PSII photochemistry was analysed from measurements of net oxygen exchanges and chlorophyll fluorescence. The Cu 2+ concentrations required to obtain 100% mortality were 15 x 10 to the second to 10 to the fourth times lower than those of K+ and Na+. Respiration was slightly affected whatever the salt concentration, while photosynthesis could be totally inhibited depending on the applied treatment. Changes in the structure of the Ribulose-1,5-biphosphate carboxylase/oxygenase (RubisCO, EC: 4.1.1.39) were also detected when C. taxifolia underwent cation treatments (10 mg/L CU 2+, 1 h; 20 g/L K+, 3 h; 20 g/L Na+, 1 h). Given the high concentration and long incubation periods required with K+ and Na+ ions, these cations are not suitable to be used in situ. Our results make possible the utilisation of copper cations following technical approaches such as ion-exchange textile covers, which allows a controlled release of cupric ions without dissemination in the marine environment. (Résumé d'auteur

Deacidification of clarified passion fruit juice using different configuratons of electrodialysis

The deacidification of clarified passion fruit juice (P edulis v flavicarpa) was investigated using the electrodialysis process (ED). Different stack configurations like conventional electrodialysis (ED2C), three compartments electrodialysis (ED3C) and electrodialysis with bipolar membranes (EDBM3C, EDBM2C) were tested. The conventional electrodialysis did not allow the deacidification of the clarified juice, whilst with the other configurations the pH of juice was increased from 2.9 (initial value) to 4.0 (target level). The ED performances were evaluated as a function of the nature of the anion exchange membrane (AEM), flow rate and current density. The physico-chemical and sensorial properties of the deacidified juices were similar: the titrable acidity was reduced from 4.3 to 1.14% w/w, the dry soluble extract varied from 13.2 to 11% w/w, the anion concentration was significantly decreased (60% of organic and 85% of inorganic anions were eliminated), the cation concentration remained inchanged, except for the sodium concentration that increased by using ED3C and EDBM3C configurations. The aroma of the passion fruit juice was preserved after treatment whatever the ED configuration used. The EDBM2C configuration deserves a special attention because the consumption of chemicals is totally eliminated and a valuable solution of citric acid with 89% of purity can be produced. (Résumé d'auteur