PHOTOSYNTHETIC CHARACTERISTICS AND GROWTH OF ALGINATE-IMMOBILIZED Scenedesmus obliquus

摘要

The microalgae Scenedesmus obliquus was immobilized in Ca-alginate beads at two stocking cell densities (6.7 x 10(5) and 1.5 x 10(6) cell bead(-1)). The photosynthetic rate (P), the initial slope of the photosynthesis (alpha), and the threshold for irradiance-saturated photosynthesis (E-k) were determined; later, the growth and protein content for S. obliquus immobilized in beads-alginate under two light intensities (135 and 200 mu E m(2) S-1) was evaluated using stocking cell densities that had previously presented the largest photosynthetic rate. Results showed than photosynthetic rates (P) and alpha of cells immobilized in beads at low stocking density (0.14 mu mol O-2 h(-1) 10(-6) cells and 0.00056) were greater than in beads with high stocking density (0.02 mu mol O-2 h(-1) 10(-6) cells and 5x10(-5)). Therefore, the beads at low stocking density were selected to be cultured under two light intensities (135 and 200 mu E m(-2) s(-1)). Both irradiances showed no significant differences on growth rates (0.157 d(-1) and 0.172 d(-1)) and protein content (15-16 % of dry-weight biomass), which represents only around 5.14-4.73 mg L-1 as N-protein of the total nitrogen removed from medium. This suggests that the light intensity within the limitation area described in the waves P-I did not affect the growth and content of protein when low cells stocking density beads are used. Therefore, it was concluded that the light intensities selected in the present study not had significant effects in the growth and protein content in beads with low cells stocking.