Culture and nitrite uptake in immobilized Scenedesmus obliquus

Abstract

The green alga Scenedesmus obliquus was immobilized in Ca-alginate beads. The cell growth after immobilization was studied by cell counting. The nitrite uptake was not affected by immobilization, except that a longer lag phase was observed in immobilized cells than in free ones. That result could be due to a barrier effect of the matrix against nitrite diffusion inside the beads. The treatment of cells by glycerol prior to their immobilization in a batch reactor induced an increase of nitrite uptake by the cells. This effect disappeared after a few runs. The glycerol effect on specific rates seemed also to decrease when the number of immobilized cells increased. This decrease can be related to the decrease of light efficiency as well as substrate accessibility when a high cell concentration was used. Several alternating runs of Tris-HCl buffer containing nitrite growth medium depleted in combined nitrogen were tested. Cellular growth occurred inside the beads up to a maximum followed by a decrease of cell number in the beads.