Effects of light and nitrogen availability on photosynthetic efficiency and fatty acid content of three original benthic diatom strains

Microalgal biotechnology has gained considerable importance in recent decades. Applications range from simple biomass production for food and animal feed to valuable products for fuel, pharmaceuticals, health, biomolecules and materials relevant to nanotechnology. There are few reports of the exploration of wider microalgae biodiversity in the literature on high value microalgal compounds, however, because it is believed that there is little to be gained in terms of biomass productivity by examining new strains. Still, without diversity, innovation in biotechnology applications is currently limited. Using microalgal diversity is a very promising way to match species and processes for a specific biotechnological application. In this context, three benthic marine diatom strains (Entomoneis paludosa NCC18.2, Nitzschia alexandrina NCC33, and Staurosira sp NCC182) were selected for their lipid production and growth capacities. Using PAM fluorometry and FTIR spectroscopy, this study investigated the impact of nitrogen repletion and depletion as well as light intensity (30, 100, and 400 μmol.photons.m-2.s-1) on their growth, photosynthetic performance and macromolecular content, with the aim of improving the quality of their lipid composition. Results suggest that under high light and nitrogen limitation, the photosynthetic machinery is negatively impacted, leading cells to reduce their growth and accumulate lipids and/or carbohydrates. However, increasing lipid content under stressful conditions does not increase the production of lipids of interest: PUFA, ARA and EPA production decreases. Culture conditions to optimize production of such fatty acids in these three original strains led to a balance between economic and ecophysiological constraints: low light and no nitrogen limitation led to better photosynthetic capacities associated with energy savings, and hence a more profitable approach

New 17-Methyl-13-Octadecenoic and 3,16-Docosadienoic Acids from the Sponge Polymastia penicillus

The phospholipid fatty acid composition of the NorthEast Atlantic sponge Polymastia penicillus (South Brittany, France) was investigated. Sixty fatty acids (FA) were identified as methyl esters (FAME) and N-acyl pyrrolidides (NAP) by gas chromatography-mass spectrometry (GC/MS), including eight D5,9 unsaturated FA and three long-chain 2-hydroxylated FA. The major phospholipid FA were palmitic (14.3% of the total FA mixture), vaccenic (12.7%), 15(Z)-docosenoic (13.4%) and 5(Z),9(Z)-hexacosadienoic (13.3%) acids. In addition to the iso-and anteiso-branched saturated FA, several unusual short-chain branched saturated FA were identified. In addition to the known D5,9 FA, and interestingly regarding their identification by GC-MS as N-acyl pyrrolidides, was the co-occurrence of unusual FA possessing a D3, D4 and D5 double bond such as iso-4-pentadecenoic, iso-5-heptadecenoic, anteiso-5-heptadecenoic and two new compounds, not hitherto found in nature, namely 17methyl-13-octadecenoic (0.8%) and 3,16-docosadienoic (1.1%) acids

New 2-methyl-13-icosenoic acid from the temperate calcisponge Leuconia johnstoni.

International audienceThe fatty acid composition of the temperate calcareous marine sponge Leuconia johnstoni Carter 1871 (Calcaronea, Calcarea) was characterized for the first time in specimens collected off the Brittany coast of France over four years from October 2005 to September 2008. Forty-one fatty acids (FA) with chain lengths ranging from C₁₄ to C₂₂ were identified as fatty methyl esters (FAME) and N-acyl pyrrolidide (NAP) derivatives by gas chromatography-mass spectrometry (GC-MS). Twenty-two saturated fatty acids (SFA) were identified accounting for 52.1-59.0% of the total FA and dimethylacetals (DMA). In addition, among the SFA, we noticed the presence of numerous methyl-branched iso and anteiso FA, suggesting a large number of associated bacteria within L. johnstoni. Thirteen monounsaturated fatty acids (MUFA, 28.0-36.0% of total FA + DMA) were also identified as well as six polyunsaturated fatty acids (PUFA, 4.0-8.2%). A noticeable DMA was detected at a high level, particularly in September 2008 (11.8%), indicating the presence of plasmalogens in this sponge species. This calcareous sponge lacked the non-methylene-interrupted FA (NMI FA) with a Δ5,9 system typical of siliceous Demosponges and Hexactinellids. The occurrence of the unusual 8,13-octadecadienoic acid was reported for the first time as a minor PUFA in a calcareous sponge. The major FA, representing 20-25% of this sponge FA, was identified as the new 2-methyl-13-icosenoic acid from mass spectra of its methyl ester and its corresponding N-acyl pyrrolidide derivatives as well as a dimethyl disulfide adduct

Multiple Beneficial Lipids Including Lecithin Detected in the Edible Invasive Mollusk Crepidula fornicata from the French Northeastern Atlantic Coast

The invasive mollusk Crepidula fornicata, occurring in large amounts in bays along the French Northeastern Atlantic coasts, may have huge environmental effects in highly productive ecosystems where shellfish are exploited. The present study aims at determining the potential economic value of this marine species in terms of exploitable substances with high added value. Lipid content and phospholipid (PL) composition of this mollusk collected on the Bourgneuf Bay were studied through four seasons. Winter specimens contained the highest lipid levels (5.3% dry weight), including 69% of PLs. Phosphatidylcholine (PC) was the major PL class all year, accounting for 63.9% to 88.9% of total PLs. Consequently, the winter specimens were then investigated for PL fatty acids (FAs), and free sterols. Dimethylacetals (DMAs) were present (10.7% of PL FA + DMA mixture) revealing the occurrence of plasmalogens. More than forty FAs were identified, including 20:5n-3 (9.4%) and 22:6n-3 (7.3%) acids. Fourteen free sterols were present, including cholesterol at 31.3% of the sterol mixture and about 40% of phytosterols. These data on lipids of C. fornicata demonstrate their positive attributes for human nutrition and health. The PL mixture, rich in PC and polyunsaturated FAs, offers an interesting alternative source of high value-added marine lecithin

Exploitable Lipids and Fatty Acids in the Invasive Oyster Crassostrea gigas on the French Atlantic Coast

Economic exploitation is one means to offset the cost of controlling invasive species, such as the introduced Pacific oyster (Crassostrea gigas Thunberg) on the French Atlantic coast. Total lipid and phospholipid (PL) fatty acids (FAs) and sterols were examined in an invasive population of C. gigas in Bourgneuf Bay, France, over four successive seasons, with a view to identify possible sources of exploitable substances. The total lipid level (% dry weight) varied from 7.1% (winter) to 8.6% (spring). Of this, PLs accounted for 28.1% (spring) to 50.4% (winter). Phosphatidylcholine was the dominant PL throughout the year (up to 74% of total PLs in winter). Plasmalogens were identified throughout the year as a series of eleven dimethylacetals (DMAs) with chain lengths between C16 and C20 (up to 14.5% of PL FAs + DMAs in winter). Thirty-seven FAs were identified in the PL FAs. Eicosapentaenoic acid (20:5n-3 EPA/7.53% to 14.5%) and docosahexaenoic acid (22:6n-3 DHA/5.51% to 9.5%) were the dominant polyunsaturated FAs in all seasons. Two non-methylene-interrupted dienoic (NMID) FAs were identified in all seasons: 7,13-docosadienoic and 7,15-docosadienoic acids, the latter being present at relatively high levels (up to 9.6% in winter). Twenty free sterols were identified, including cholesterol at 29.9% of the sterol mixture and about 33% of phytosterols. C. gigas tissues thus contained exploitable lipids for health benefits or as a potential source of high-quality commercial lecithin

Nitrogen and phosphorus limitations induce carbon partitioning and membrane lipid remodelling in the marine diatom Phaeodactylum tricornutum

Nitrogen (N) and phosphorus (P) limitations induce triacylglycerol (TAG) accumulation and membrane lipid remodelling in the marine diatom Phaeodactylum tricornutum. However, a clear understanding of the metabolic reorientation is still lacking. Carbon partitioning is of great interest because this microalga produces various highly valuable molecules such as lipids and polyunsaturated fatty acids. This study compared growth, photosynthetic activity, biochemical and transcriptional responses of P. tricornutum throughout batch culture under N or P limitation. The integrated results show that the photosynthetic intensity was greatly reduced under N or P limitation. Under N limitation, the degradation and re-use of cellular N-containing compounds contributed to TAG accumulation, whilst P limitation favoured TAG accumulation due to the efficiency of carbon fixation, without massive degradation of essential compounds at cellular level. There was no difference in the partitioning of carbon to neutral lipids between N and P limitation. Substitution of phospholipids with betaine lipids appeared to be a P-specific acclimation strategy in P. tricornutum, which was largely regulated at the gene expression level. Betaine lipid synthesis was induced by P limitation. The lipid remodelling began once the medium became deficient in P. While the phospholipid biosynthesis pathway was not completely inhibited, a shift of lipid classes occurred immediately after their synthesis via phospholipid-recycling mechanisms