VARIATIONS IN THE BIOCHEMICAL PROFILE OF THE MARINE MICROALGA DUNALIELLA-TERTIOLECTA (BUTCHER) CULTURED WITH DIFFERENT NUTRIENT CONCENTRATIONS AND UREA AS A NITROGEN-SOURCE

Variations in the biochemical profile of the marine microalga Dunaliel la tertiolecta (Butcher) cultured with different nutrient concentratio ns and urea as a nitrogen source. Cultures of the marine microalga Dun aliella tertiolecta were grown in a urea-based medium, using four nutr ient concentrations following a geometrical progression of order 2, ex pressed as x1, x2, x4 and x8, in order to obtain a maximum biomass pro duction and to find out its biochemical variability. The nutrient conc entration had little effect on the growth rate in the logarithmic phas e, with values between 0.40 and 0.44 doublings.day-1. Maximum cellular densities of 7.53 x 10(6) and 7.96x10(6) cells.ml-1 were obtained in x2 and x4 cultures (corresponding to 2 and 4 mM of urea). Differences in biochemical composition were found in function of the nutrient conc entration. Protein content reached maximum values in the stationary ph ase in x4 and x8 cultures, with 29.56 and 29.28 pg.cell-1. The maximum value of carbohydrates was obtained in x1 cultures, with 14.38 pg.cel l-1. Maximum lipids per cell were obtained in the stationary phase in cultures with the higher nutrient concentration assayed (x8), with 23. 12 pg.cell-1. Cultures at the lower nutrient concentration assayed (x1 ) showed a nitrogen deficiency, with cells with low protein and high c arbohydrate content at the stationary phase.