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- Marine microalgae monosaccharide fluctuations as a stress response to nutrients inputsPublication . Fernandes, Tomásia; Fernandes, Igor; Andrade, Carlos A. P.; Ferreira, Artur; Cordeiro, NereidaThe monosaccharide patterns of the microalgae species Nannochloropsis gaditana, Rhodomonas marina and Isochrysis sp. were assessed, to verify if nutrients availability had an impact on these parameters. Isochrysis sp. and Rhodomonas marina monosaccharides content decreased 13–94% as the nutrients availability increased. The relative abundance of monosaccharides depicted that, at low nutrients availabilities, Rhodomonas marina and Isochrysis sp. had preference for glucans synthesis, accounting for up to 75% of the monosaccharides detected. Linking the monosaccharides trends with the phylogeny and glycolipid data, it was possible to establish which monosaccharides had a structural and/or storage role in the microalgae studied. Thermal analysis revealed that the microalgae submitted to low nutrient input treatments presented a reduced assimilation of the inorganic compounds. Nutrient concentrations affected microalgae monosaccharide patterns, highlighting their taxonomic differences.
- Assessing the impact of sulfur concentrations on growth and biochemical composition of three marine microalgaePublication . Fernandes, Tomásia; Fernandes, Igor; Andrade, Carlos A. P.; Cordeiro, NereidaThe elemental stoichiometry, growth and biochemical composition of Nannochloropsis gaditana, Rhodomonas marina and Isochrysis sp. were studied in batch cultures against different nitrogen and sulfur molar ratios (N:S) imposed in their surroundings. In N. gaditana, treatments with low N:S lead to an increase in carbon:sulfur (C:S) and N:S molar ratios up to 95 and 81%, respectively. This was reflected in lipid and protein contents which increased up to 67 and 55%, respectively. Moreover, polyunsaturated fatty acids, as well as its precursors, increased in low N/S treatments. In R. marina, the treatments applied promptly the decrease of both C:S and N:S ratios to 70 and 68%, respectively. Nevertheless, eicosapentaenoic:arachidonic acid ratio increased with N:S treatments by three and a half fold. In Isochrysis sp., the elemental stoichiometry was constrained against treatments until the highest sulfur input. Overall, sulfur supply highlighted microalgae taxonomic differences and suggested that biochemical control is required, even in nutrient replete conditions, to fully exploit their potential as added value biomachineries.
- Changes in fatty acid biosynthesis in marine microalgae as a response to medium nutrient availabilityPublication . Fernandes, Tomásia; Fernandes, Igor; Andrade, Carlos A. P.; Cordeiro, NereidaTo maximize and enhance the fatty acid (FA) profiles of microalgae, it is crucial to understand the metabolic path ways that lead to high levels of the desired product. Nannochloropsis gaditana, Rhodomonas marina, and Isochrysis sp. were cultivated in media with various nutrient concentrations, and the biomass was analyzed for protein and fatty acid contents. The long chain polyunsaturated fatty acid (LC-PUFA) and protein contents were maximized in media with high nutrient concentrations. Under these conditions, the reduction in the (SFA + MUFA)/PUFA ratio (by as much as 83%) indicated that R. marina and N. gaditana shifted preference towards PUFA synthesis. The ∑ω3/∑ω6 ratio indicated that R. marina preferentially synthesized ω3 FA towards high nutrient concentrations (depicted by an eightfold increase) in contrast to Isochrysis sp. (which yielded a 35% reduction). In addition, the limitations of LC-PUFA biosynthesis at the level of its precursors (e.g. C18:2ω6, C18:3ω3, C18:4ω3) and further conversion to LC-PUFA as nutrients were increased, suggesting that external variations induced changes in the sets of enzymes that maintain the desaturation and elongation pathways of FA. The present study provides novel insights into the regulation of LC-PUFA biosynthesis and facilitates the modeling of microalgal FA patterns depending on the field of application.
- Marine microalgae growth and carbon partitioning as a function of nutrient availabilityPublication . Fernandes, Tomásia; Fernandes, Igor; Andrade, Carlos A. P.; Cordeiro, NereidaTo understand in which way the structural differences of three marine microalgae (Nannochloropsis gaditana, Rhodomonas marina and Isochrysis sp.) affect their carbon partitioning, growth and applicability; a stoichiometric imbalance was imposed by steady carbon and other nutrients variation. Towards high nutrients concentrations/low carbon availability a decrease of 12-51% in C/N microalgae ratio was observed and maximum cell densities were achieved. Moreover, linear correlation between the nutrient input and microalgae protein content were observed. The macromolecular ratios pointed that carbohydrate was the main contributor for the C/N decrement. Although lipid content in R. marina remained constant throughout the experiment, a rise of 37-107% in N. gaditana and Isochrysis sp. was verified. Lipid fractions revealed high percentages of glycolipids in all microalgae (57-73% of total lipids). The present study shows an easy way to understand and modulate microalgae carbon partitioning relying on the field of application.