Abstract :
[en] FOTOBIOMAT is a project funded by the Région Wallonne (Greenomat programme), Belgium. Its main goal is the conception of a photobioreactor using immobilized biomass (Dunaliella sp.) in which the microalgae are entrapped in a hybrid material (beads in suspension). Those beads are synthetized by coacervation process of a mixture containing alginate, silica and microalgae. The cells will stay photosynthetically active during long periods (> 6 months) and able to produce -carotene in (nearly) continuous way.
One of the crucial points of the research concerns the metabolites extraction out of the beads. In order to study this phenomenon, commercial -carotene (purchased from TCI Europe) has been entrapped in beads which are immerged in different solvents commonly used for pigment extraction out of microalgae. These are: acetone, methylethylcetone (MEC), diethylether, hexane, iso-octane, dodecane, dichloroethane, methanol, ethanol, octanol, methylterbutylether (MTBE), dimethylsuloxyde (DMSO). The extraction rate of -carotene is followed by a spectrophometer (UVmini 1240 Shimadzu). The experiment lasts one week with solvent replacement on days 4 and 5. Five of the twelve tested solvents allow the -carotene extraction out of the beads: acetone, methanol, ethanol, MTBE and DMSO. Besides -carotene extraction, part of the material is altered. When tested on beads containing Dunaliella sp. (the duration of the contact beads-solvent is 15 minutes and repeated three times) both chlorophylls and carotenoids were extracted. The experiment has been repeated three times in ten days. After this period, it has been noticed that the entrapped cells were dead.
One biocompatible solvent, the sunflower oil, has been tested successfully on free cells (carotenoid extraction without killing the algae) but the first tests on beads containing -carotene (without algae) are not relevant for the moment. Other green solvents should be tested in the future steps of the research: corn oil, ethyl lactate, ethyl acetate, d-limonene, -pinene and p-cymene possibly combined with mechanical or physico-chemical methods (e.g. ultra-sounds, electroporation, ...).
