INFLUENCE OF INORGANIC NUTRIENTS ON PARAMETERS OF BIOMASS PRODUCTION IN A LOCAL STRAIN OF THE MICROALGA SCENEDESMUS ACUMINATUS

Biotechnologies based on microalgal cell cultures have multiple applications in aquaculture, the food industry, health care, environmental management, and production of alternative energy sources. In the present study we investigated the influence of nutritional conditions on bioproductive properties of a local strain of the green microalga Scenedesmus acuminatus, grown in axenic laboratory cultures, in Bold's basal nutrient medium. Increment of nitrate concentration enhanced the biomass production, and increased protein content of the alga. Simultaneous supplement of reduced and oxidized form of inorganic nitrogen (as ammonium nitrate) did not result in an increased dry biomass, but the protein content of algal cells was significantly higher, while the carotenoid content decreased. Nitrogen deprivation increased the carotenoid pigment content of the dry algal biomass. 10 mM KHCO3 as inorganic carbon source increased biomass production, decreased protein content and did not modify significantly the carotenoid content of the alga. A higher phosphate concentration in the medium induced an increment of dry biomass and carotenoid content, but had no relevant influence on protein content. Sulphate enrichment did not modify dry biomass and carotenoid content, but caused a moderate increment of protein amount. Photosynthetic light use efficiency and vitality index of photosynthetic apparatus, evaluated with the method of induced chlorophyll fluorescence, revealed a positive influence of ammonium nitrate and of elevated nitrate content, while nitrate starvation and an excessive phosphate and sulphate supply moderately decreased the functional efficiency of light reactions of photosynthesis.