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Data of Thesis


Author: Laís Bessa dos Santos

Title: Effects of phosphorous concentration on growth and lipid synthesis in Ankistrodesmus sp.

Year: 2011.    Full text (in Portuguese)


Microalgae are micro-organisms promising as an alternative raw material for biodiesel production. The energy matrix is in process of change and biodegradable and renewable sources are objects of many studies nowadays. The nutritional stress is a commonly studied physiological tool to stimulate the synthesis of lipid reserves by microalgae. What is fundamental to the use of microalgae biomass for the biodiesel production. The objective of this study was to evaluate the effects of phosphorus concentration on growth and lipid synthesis by the microalgae Ankistrodesmus sp. (strain ANRF-01). For this purpose, the ASM-1 medium was manipulated relative to its initial concentration of orthophosphate. So, we obtained three different concentrations of phosphorus in the culture medium of the strain studied. Treatments appointed control, P10 and P50 started the experiment with values of 227 μM, 22.7 μM and 4.54 μM PO4 -3, respectively. The cultures were developed for 20 days at 24°C with constant aeration, light intensity of 500 μmoles photons.m-2.s- 1, photoperiod of 12 h, initial pH 8.0 and 6 L volume of culture. Analysis were developed for cell growth, varying the concentration of chlorophyll a, carbohydrates and nutrients (nitrate and phosphate). The lipids were analyzed in relation to the percentage of crude extract and its classes of fatty acids. In the results we observed more cells and biomass for the control condition. The condition with the highest nutritional limitation (P50) showed a lower amount of biomass, but the conditions P10 and P50 showed biomass values close to the 9 th day of culture (224 and 216 mg / L, respectively). The highest values of lipids produced were detected in the P50 treatment. Among the days sampled for analysis of lipids, the 9th day of culture was the most promising for the lipid content and fatty acid profile of interest. There is need for significant amount of biomass, a high content of lipids and fatty acid profile of interest to the economical production of biodiesel from microalgae. Thus, the study indicates that the condition P50 on the 9th day (stationary phase) would be more appropriate as an alternative source, in a future production of biodiesel on a large scale. Further studies should be conducted to give a better basis on the physiological conditions of cultivation of these organisms for the biotechnology purpose. Key words: microalgae, lipids, phosphorus concentration and biodiesel.