Como a manipulação da temperatura e dos nutrientes pode influenciar no teor de lipídios produzidos em culturas de microalgas de água doce?

Abstract

Currently, there is a growing need for the search of viable alternative energy, affordable and sustainable substitute for fossil fuels. One option is the production of energetic biomass by microalgae, which is considered a clean alternative compared to others that require large areas for cultivation and that generate environmental impacts. In this context, the research aimed to evaluate the influence of temperature and nutrients on lipid content of cultured species of freshwater microalgae, in order to use these lipids for biodiesel production. For this purpose, two strains of Monoraphidium contortum, a strain containing Chlorella vulgaris and Desmodesmus quadricauda and other of Microcystis aeruginosa, were maintained in the laboratory for six days, in five culture media, modified ASM-1 (control, with high concentrations of phosphate and nitrate; Pdeficient; non-limiting concentration of phosphate; N-deficient; non-limiting nitrate). Later, they were exposed to temperatures of 13 ° C, 25 ° C (control) and 37 ° C for eight days (n = 3). The lipid extraction was performed on the 1st, 4th and 8th day of the experiment following the method commonly used with cold solvent (a mixture of methanol and chloroform). There was no significant lipid variation among strains (p> 0.05). On average, the highest total lipid yields were observed when the strains were maintained at 13 ° C and in the medium with intermediate concentration and nonlimiting nitrate. We found significant variation in total lipid percentage in relation to day that the extraction was performed (p<0,05). The lipid percentage varied depending on the concentration of algal biomass (p<0,05). The strain of Microcystis aeruginosa showed high total lipid content, when maintained in culture medium with abnormal concentrations of nitrate and phosphate, contrary to the literature data. The strains can be considered as potential lipid producers since the culture medium, the temperature and the time for extraction of lipids are correctly established. This study showed that manipulations of determining factors might induce higher lipid concentration, optimizing the total production in order to use this raw material for biodiesel.