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- Metabolic relationships between macro- and micronutrients, and the eicosapentaenoic acid and docosahexaenoic acid contents of Pavlova LutheriPublication . Carvalho, Ana P.; Pontes, Isabel; Gaspar, Hugo; Malcata, F. XavierThe use of specific microalgae as sources of polyunsaturated fatty acids (PUFA), for incorporation in either aquaculture or human diets, has been receiving increasing interest. The fatty acid profile of intracellular fats in a given species can, within certain limits, be modulated via manipulation of the culture growth conditions, namely nutrient availability. In attempts to shed further light on the effects of chemical parameters upon microalgal metabolism, correlations between the components of a medium and the resulting biomass yield, as well as the eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) contents are presented, using Pavlova lutheri as model system. Although several studies of individual nutrients have been published previously, the effects of variation of all medium components upon fatty acid production are systematically presented here, apparently for the first time. The optimum formulation to optimise EPA and DHA contents should consider the buffering agent, since some of them are toxic to the cells; P. lutheri was able to use several nitrogen sources, yielding equivalent amounts of EPA and DHA; synthesis of EPA was induced in culture media under low salinity, whereas a trend could be noticed between decreasing yields of EPA and increasing concentrations of N, at 0.15 g L−1 of P. Regarding the micronutrient composition, a culture medium lacking sulphur was unable to sustain cellular growth, whereas cultures deprived of either calcium, iron or manganese revealed a statistically significant decrease in cellular yields relative to those possessing such minerals; conversely, those cultures without boron produced higher cell numbers than those containing this element. Media deprived of boron, molybdenum or copper led to increases of the relative amounts of both EPA and DHA, whereas calcium deficiency decreased the levels of those PUFA.
- Effect of culture media on production of polyunsaturated fatty acids by pavlova lutheriPublication . Carvalho, Ana P.; Malcata, F. XavierUse of microscopic algae as sources of polyunsaturated fatty acids for incorporation as feed additive in aquaculture has received increasing interest owing to beneficial effects upon growth rates of zooplankton. However, the biochemical composition of marine algae is a function of the composition of the culture medium. Pavlova lutheri is particularly interesting because it is able to modulate the fatty acid profile of its lipidic fraction when cultured with various nutrient media. Three enriched seawater media (i.e. GPM, f/2 and MN) and one synthetic medium (i.e. ASW), covering considerable quantitative and qualitative ranges of nutrients, were tested in order to determine the medium compositions that stimulate production of such polyunsaturated fatty acids as EPA and DHA, and the biochemical compositions of the algae grown in each were monitored accordingly. Relationships between the mineral components of the medium and the resulting biomass yield, as well as the biochemical profile and the polyunsaturated fatty acid productivity, are tentatively presented in attempts to shed further light on the effects of the processing environment upon microalgae. Statistical analyses of the experimental results have indicated that GPM provides the best compromise in terms of cell yield (12.1 × 106 cell mL−1) and polyunsaturated fatty acid productivities (0.502 mg l−1 d−1 and 0.228 mg l−1 d−1 in EPA and DHA, respectively). In addition, GPM is a simple medium, mainly composed of seawater, nitrogen and phosphorus, thus having a low production cost and being easy to prepare in industrial settings, so it is suitable for general use in aquaculture of marine species.
- Optimization of ω-3 fatty acid production by microalgae: Crossover effects of CO2 and light intensity under batch and continuous cultivation modesPublication . Carvalho, Ana P.; Malcata, F. XavierThe microalga Pavlova lutheri is a potential source of economically valuable docosahexaenoic and eicosapentaenoic acids. Specific chemical and physical culture conditions may enhance their biochemical synthesis. There are studies relating the effect of CO2 on growth; however, this parameter should not be assessed independently, as its effect strongly depends on the light intensity available. In this research, the combined effects of light intensity and CO2 content on growth and fatty acid profile in P. lutheri were ascertained, in order to optimize polyunsaturated fatty acid production. The influence of the operation mode was also tested via growing the cultures by batch and by continuous cultivation. Higher light intensities associated with lower dilution rates promoted increases in both cell population and weight per cell. Increased levels of CO2 favored the total lipid content, but decreased the amounts of polyunsaturated fatty acids. Mass productivities of eicosapentaenoic acid (3.61 ± 0.04 mg . L⁻¹ . d⁻¹) and docosahexaenoic acid (1.29 ± 0.01 mg . L⁻¹. d⁻¹) were obtained in cultures supplied with 0.5% (v/v) CO2, at a dilution rate of 0.297 d)1 and a light intensity of 120 µE . m-2 . s-1.
- Metabolic relationships between mineral composition of medium and polyunsaturated fatty acid profile of Pavlova lutheriPublication . Carvalho, Ana P.; Malcata, F. Xavier