10452 2013 9454 MOESM1 Esm

Journal of Applied Phycology, 2012

Since the fatty acid ester profile of a given biofuel is relatively consistent with the source's fatty acid profile, the properties of the biodiesel produced from a particular feedstock exhibit predictable quality. Thus, lipid fractions and the fatty acid composition of stationary growth-phase cultures of the local strains of the diatoms Skeletonema costatum and Navicula gregaria were analysed to evaluate their suitability as biodiesel feedstock. Total lipid content was 20.83 pg cell −1 in S. costatum and 19.17 pg cell −1 in N. gregaria. Neutral lipids were the main fraction of total lipids in both species, accounting for ca. 65% and 76%, respectively. S. costatum was predominant in saturated fatty acids (SFAs; 43.48 %) and monounsaturated fatty acids (MUFAs; 40.11%), while N. gregaria was predominant in MUFAs (54.85%), followed by SFAs (33.42%). In S. costatum, the main fatty acids in neutral lipid fraction were myristic, palmitic, palmitoleic and oleic acids, while the main ones in N. gregaria were palmitic and palmitoleic acids. The oils extracted from these species presented linolenic acid contents within biodiesel's quality specifications. However, in neutral lipid fraction both species showed eicosapentaenoic acid levels higher than the required limit. The lipid quality analysed in both species suggests that a biodiesel derived from these oils may present an acceptable cetane number, but likely poor coldflow properties. This baseline information is useful for future research tending to find more suitable conditions in order to improve oil yield. In addition, both estuarine species neither compete with agriculture for food nor require farmland nor fresh water.

The effect of growth phase and environmental factors on growth, fatty acid composition and DHA/EPA ratio of Phaeodactylum tricornutum Bohlin was studied. Microalgae were grown in laboratory batch cultures in f/2 medium. Cultures were grown at different salinities (15, 20, 28, and 35 ppt), nitrogen (N) concentrations (1.24, 12.35, 24.70 and 49.40 mg L −1), light intensities (50, 100 and 150 μmol m −2 s −1 ; 14:10 h light:dark cycle) and temperatures (15, 20 and 25 °C), and sampled at different points of the respective growth phases (inoculums, early-linear, middle-linear and late-linear phases). Samples were analyzed for biomass weight, fatty acid composition and total fatty acid content (TFAC). The main fatty acids in all culture conditions were C14:0 (5.25%-6.04%), C16:0.01%) and eicosapentaenoic acid (EPA, 22.81%-30.72%). The percentage of polyunsaturated fatty acids (PUFAs) was reduced while that of monounsaturated fatty acid acids (MUFAs) and TFACs increased with culture time. Salinity had no serious effect on fatty acid composition, however, a significant decline of TFAC was observed at the lowest salinity (p b 0.05). Significant (p b 0.05) increases of the relative contents of SFAs and MUFAs and a decrease of PUFAs were observed under N-limitation condition. The percentage of docosahexaenoic acid (DHA) was significantly enhanced with increasing light intensity (p b 0.05), while that of DHA, EPA and PUFA decreased significantly with increasing temperature (p b 0.05). DHA/EPA ratio tended to rise initially and fall later with increasing growth time, and reached the highest level with the lowest salinity, and the lowest temperature and initial N concentration, revealing a possible cell response to the stress brought from the unfavorable conditions. In conclusion, this study demonstrates the variation of growth, fatty acid composition and DHA/EPA ratio with growth phase and environmental factors in P. tricornutum, benefiting the production of PUFA-rich microalgae, with a DHA/EPA ratio optimal for aquaculture live food. Statement of relevance We conducted detailed analysis on the effect of the culture conditions on growth, fatty acid composition and DHA/EPA ratio in Phaeodactylum tricornutum, a widely used microalga for aquaculture feedstuff in China. We found that the environmental stress conditions increased DHA/EPA ratio. The research will benefit the production of PUFA-rich and DHA/EPA-ratio-optimal microalgae for aquaculture feedstuff.

The marine diatom, Phaeodactylum tricornutum had a high lipid content accumulation under photoautotrophically nitrogen-deficient cultivation. The lipid content (Y P/X ; 53.04 ± 3.26%) was highest with a specific rate of lipid production (q P ; 1.50 ± 0.12 Â 10 À3 mg/mg h), attained at the minimized specific growth rate (m; 0.87 ± 0.13 Â 10 À2 /h) after 504 h of cultivation. When the specific growth rate (m; 2.47 ± 0.02 Â 10 À2 /h) was maximized in nitrogen-sufficient culture (32.09 mg/L NaNO 3 ), the specific rate of lipid production (q P ; 0.42 ± 0.19 Â 10 À3 mg/mg h) was lowered. In this work, the nitrogen concentration with fixed phosphorus concentration was used to monitor the lipid accumulation, as the lower nitrogen concentration favored a higher lipid content percentage, compared with a higher nitrogen concentration. Under nitrogen-deficient conditions, P. tricornutum produced a large amount of saturated fatty acids, mainly as palmitic acid (C16:0), while palmitoleic acid (C16:1c) was found to be the sole unsaturated fatty acid. On the other hand, eicosapentaenoic acid (C20:5u3c) was produced in large amounts when there was sufficient nitrogen. Since the biodiesel was qualified based on the fatty acid methyl ester composition, the oil from algae cultured under nitrogen-deficient conditions were considered to meet the biodiesel standard. Thus, P. tricornutum optimally cultivated under nitrogendeficient conditions can accumulate a high oil content, which demonstrates its potential as a biodiesel feedstock.

Marine Biology, 2008

We measured development, growth and juvenile mortality of the common copepod Temora longicornis on 11 diVerent monospeciWc diatom diets in order to estimate (1) how common the negative eVects of diatoms are on the development of this copepod and (2) whether the arrested development is connected to deleterious polyunsaturated aldehydes (PUA) or food nutritional quality. Four diatom species (Thalassiosira weissXogii, Thalassiosira rotula CCMP1647, Leptocylindricus danicus CCPM469 and Skeletonema costatum CCMP1281) supported complete development, whereas development failed in or before metamorphosis on seven diatom species/strains (Chaetoceros aYnis CCMP158, C. decipiens CCMP173, C. socialis, T. rotula CCMP1018, Thalassiosira pseudonana CCMP1010 and CCMP1335). However, four out of these seven species were not ingested by nauplii, either due to morphology (Chaetoceros spp.) or large size (T. pseudonana CCMP1010). The growth rate did not correlate with the ingestion rate of PUA, neither with ingestion of food mineral (nitrogen) nor with biochemical (polyunsaturated fatty acids, sterols) components. We show that, although some diatoms are of inferior food quality, this is unlikely to be connected to toxicity or due to a direct limitation by a single food nutritional compound.

International Journal of Fisheries and Aquaculture, 2012

Five native species of marine microalgae were batch cultured and their chemical composition was measured in different growth phases. The highest cell yield was recorded in Chlorella sp. Chlorella sp. and Bellerochea sp. showed a reduction of the mean cell volume throughout growth. All microalgae showed protein as the main chemical component, with peaks in the exponential growth phase. The same was found for chlorophyll. Carbohydrates (Chlorella sp.), ash (Bellerochea sp. and Chlorella sp.), and lipids (Rhodomonas sp. and Thalassiosira sp.) were relatively high in some of the species, at least in one of the growth phases. The carbohydrate content increased throughout growth, but no clear relationship among growth, total lipid and ash content was identified. Total saturated fatty acids were higher in the exponential growth phase of all species, decreasing throughout growth. Rhodomonas sp. showed high levels of polyunsaturated fatty acid (PUFA), but low percentages of some essential fatty acids. Bellerochea sp., Chaetoceros sp. and Chlorella sp. showed low percentages of total PUFA, but all essential fatty acids were present, except for the green alga. Current results may contribute to selecting strains that possess suitable chemical composition and fast growth, useful characteristics for the sustainable use of native species in aquaculture.

Nitrogen deficiency can increase the lipid content in certain microalgae species, including diatoms. However, the molecular and metabolic basis of such changes remains rather unclear. We analyzed strains of freshwater Nitzschia palea collected from a eutrophic pond and from an artificial rock. The habitats, differing in light and nutrient availability, lead to two metabolically distinct strains, BR006 and BR022. Differential accumulation of primary compounds, membrane lipid composition and fatty acid saturation were observed. Metabolic and biophysical analysis demonstrated differential sensitivity to N regimes: depleted, replete and saturated. Whereas N depletion leads to typical stress-related responses in both strains, including reduction of protein and photosyn-thesis, the response observed in BR006 is far more severe. Our results demonstrated that these strains developed distinct metabolic responses to N conditions. BR022 is able to maintain cellular homeostasis and slows down growth according to N availability. In contrast, BR006 maximizes growth rate even under N limitation, by triggering stress response, relocating carbon pool to lipid compounds and quickly reaching growth arrest after N exhaustion. We identified a relationship between habitat characteristics and metabolic responses, providing a metabolic perspective on ecological plasticity of N. palea, which helps it to survive a wide range of habitats.

Bioresource Technology, 2013

h i g h l i g h t s " Three marine microalgae species were analyzed as a potential biodiesel feedstock. " The chosen harvesting technique has important influences on biomass composition. " Three solvent lipid extraction techniques were analyzed. " Direct transesterification method found as a promising technique to produce FAME.

izlazi u samo …, 2011

The relationship between changes in lipid classes and phytoplankton composition and abundance in the northern Adriatic was studied during spring and summer 2008 at two stations with different nutrient levels, i.e. at the western mesotrophic and eastern oligotrophic areas. Changes in the phytoplankton community depended on temporal surface nutrient depletion and bottom accumulation; that is, microphytoplankton, mainly diatoms Pseudo-nitzschia sp., developed at nutrient richer surface layers of the mesotrophic area in spring and at deeper layers of the oligotrophic site in late summer. In other periods nanophytoplankton dominated. Dissolved organic carbon (DOC) and lipid content were comparable for the two stations, while particulate organic carbon (POC) was richer at the mesotrophic side. Total lipid concentrations varied in the range from 8.0 to 92.2 mg l À1 and from 16.9 to 76.9 mg l À1 in the dissolved and particulate fractions, respectively. DOC and POC contents were in the ranges from 0.77 to 1.58 mg l À1 and from 0.06 to 0.56 mg l À1 , respectively. Lipid and organic carbon distribution did not follow phytoplankton progression, indicating decoupling between organic matter production and decomposition throughout the investigation period. The main sources of lipids were marine phyto-plankton and bacteria. Low nutrient conditions caused increased biosynthesis of lipids. Also, increasing oligotrophy led to an increasing number of phytoplankton taxa. The synthesis and accumulation of glycolipids by the developed taxa were enhanced during nutrient exhaustion, contributing in late summer, on average, 20.2 and 22.0% at the mesotrophic and oligotrophic stations, respectively, in the particulate fraction. The distribution of bacterial lipids and lipid breakdown products implies that bacterial lipid degradation was significant in spring, while very probably lipid abiotic degradation took place during summer.

AMB Express, 2013

Long chain polyunsaturated fatty acids (LC-PUFAs) such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are considered essential omega-3 fatty acids in human nutrition. In marine microalgae EPA and/or DHA are allegedly involved in the regulation of membrane fluidity and thylakoid membrane functioning. The cellular content of EPA and DHA may therefore be enhanced at low temperature and irradiance conditions. As a result, polar and cold temperate marine microalgal species might potentially be suitable candidates for commercial EPA and DHA production, given their adaptation to low temperature and irradiance habitats. In the present study we investigated inter-and intraspecific EPA and DHA variability in five polar and (cold) temperate microalgae. Intraspecific EPA and DHA content did not vary significantly in an Antarctic (Chaetoceros brevis) and a temperate (Thalassiosira weissflogii) centric diatom after acclimation to a range of irradiance levels at two temperatures. Interspecific variability was investigated for two Antarctic (Chaetoceros brevis and Pyramimonas sp. (Prasinophyceae)) and three cold-temperate species (Thalassiosira weissflogii, Emiliania huxleyi (Prymnesiophyceae) and Fibrocapsa japonica (Raphidophyceae)) during exponential growth. Interspecific variability was shown to be much more important than intraspecific variability. Highest relative and absolute levels of DHA were measured in the prymnesiophyte E. huxleyi and the prasinophyte Pyramimonas sp., while levels of EPA were high in the raphidophyte F. japonica and the diatoms C. brevis and T. weissflogii. Yet, no significant differences in LC-PUFA content were found between polar and cold-temperate species. Also, EPA and DHA production rates varied strongly between species. Highest EPA production rate (174 μg L -1 day -1 ) was found in the Antarctic diatom Chaetoceros brevis, while DHA production was highest in the cold-temperate prymnesiophyte Emiliania huxleyi (164 μg L -1 day -1 ). We show that, following careful species selection, effective mass cultivation of marine microalgae for EPA and DHA production may be possible under low temperature and irradiance conditions.

The increasing interest for biotechnological use of microalgae demands a methodology for selection of species suitable to support the development of technologies based on the use of such non-conventional renewable raw material, i.e., green industrial applications. The vast and expanding collection of experimental data on both cell growth and biomass composition available in the literature can be used to reduce the cost of the experimental investigations required to support process engineering and optimization. Selecting the appropriate organism requires extracting useful information from such data, a cumbersome task since various multidisciplinary factors must be considered. This paper presents a computeraided methodology for selecting appropriate algal species given an energy or green chemical process application employing microalgae as a renewable raw material. The approach is ''system oriented'', based on biomass composition and chemical processing of the biomass downstream of the CO 2 biofixation and harvesting operations. Quantitative performance results are supported by professional process simulation. Besides comparison of a set of species performances, the proposed methodology also allows the discrimination among distinct algal compositions resulting from different growth conditions for a given species. Furthermore, three categories of screening metrics are proposed to be maximized by the decision making procedure in order to elicit the relevant information. To demonstrate the potential of the proposed methodology, a databank of both biochemical and elemental compositions of microalgal biomass was used in three green applications: Assessment of biomass heating value; production of syngas by gasification of the biomass; and production of Bio-H 2 . Within the accuracy of the databank employed to illustrate the procedure, the methodology selected Botryococcus braunii and Isochrysis galbana as potential promising candidates, for the three examined applications.