Aurélie Couzinet-Mossion

The study of Comorian red alga Halymenia durvillei showed a significant biochemical composition with high ash and polysaccharide content and the presence of n-3 and n-6 essential fatty acid molecules. Seasonal monitoring showed a real change in biochemical composition depending on the harvesting period. On an annual average basis, the algae contained 35.59 ± 2.55% dw ashes, 0.7 ± 0.19% dw soluble proteins, 0.27 ± 0.02% dw total lipids, and 35.09 ± 6.14% dw polysaccharides. The pigment composition was 130 µg/g dw R-phycoerythrin, 1.49 µg/g dw chlorophyll a, and 0.09 µg/g dw carotenoids. The most abundant fatty acid identified was palmitic acid (C16:0), which accounted for almost 43.33% of total fatty acids. Oleic acid (C18:1n-9) was the most abundant unsaturated fatty acid, at 11.58%. Linoleic acid (C18:2n-6) was reported to be the most abundant polyunsaturated fatty acid in Halymenia durvillei. The fatty acid profile was also characterized by arachidonic acid (C20:4n-6) and eicosapentaenoic acid (C20:5n-3).

Microalgae provide valuable bio-components with economic and environmental benefits. The monitoring of microalgal production is mostly performed using different sensors and analytical methods that, although very powerful, are limited to qualified users. This study proposes an automated Raman spectroscopy-based sensor for the online monitoring of microalgal production. For this purpose, an in situ system with a sampling station was made of a light-tight optical chamber connected to a Raman probe. Microalgal cultures were routed to this chamber by pipes connected to pumps and valves controlled and programmed by a computer. The developed approach was evaluated on Parachlorella kessleri under different culture conditions at a laboratory and an industrial algal platform. As a result, more than 4000 Raman spectra were generated and analysed by statistical methods. These spectra reflected the physiological state of the cells and demonstrate the ability of the developed sensor to monitor the physiology of microalgal cells and their intracellular molecules of interest in a complex production environment.

Sterols are the main components of the fungal membrane. Their study can be used to describe the chemical biodiversity among the strains and species or to work on antifungal treatment. Those molecules can be analyzed by gas chromatography coupled with mass spectrometry (GC–MS) as free molecules or after derivation as acetate or trimethylsilyl ether (TMSi). Here we describe how to extract sterols from fungal biomass according to its physiological form and the culture conditions (liquid and solid media). The different methodologies that can be used to obtain free sterols, acetate, and/or TMSi derivatives are presented. Identification keys using the fragmentation at 70 eV are also described. Key words Fungal sterols Extraction Saponification Acetate TMS derivatives GC–MS Identification

Marine fungi have been found in all habitats and are able to adapt to their environmental niche conditions. In this study, a combination of liquid chromatography coupled to high-resolution mass spectrometry (LC-HRMS) and gas chromatography coupled to mass spectrometry (GC-MS) analytical approaches was used to analyse the metabolic changes of a marine-sourced Penicillium restrictum strain isolated from a marine shellfish area. The P. restrictum MMS417 strain was grown on seven different media including an ecological one with two different water sources (synthetic seawater and distilled water), conditions following the One-Strain-Many-Compounds (OSMAC) approach. Extracts of all media were analysed by LC-HRMS (lipids and specialised metabolites profiling) and GC-MS (fatty acids profiling). Acquired data were analysed using a multiblock strategy to highlight metabolic modification in regard to water conditions and to environmentally relevant conditions (mussel-based culture medium). This revealed that fatty acid composition of lipids was the most altered part of the explored metabolisms whether looking to the effect of water or of environmentally relevant conditions. In particular, data showed that P. restrictum MMS417 is able to produce lipids that include fatty acids usually produced by the mussel itself. This study also provides insight into the P. restrictum adaptation to marine salinity through fatty acids alteration and shows that lipid metabolism is far more altered in an OSMAC approach than the specialized metabolism. This study finally highlights the need for using environment-mimicking culture conditions to reveal the metabolic potentialities of marine microbes.

Background: Nowadays, the efficiency of antibiotics is endangered by the development of resistant bacterial strains. Consequently, novel bioactive agents are intensively searched. Marine sponges are well-known for being major sources of bioactive compounds, including unusual sterols. Until now, among sterols, noteworthy antibacterial activity has been reported exclusively for Δ5 sterols. Objectives: This study aims to describe the steroid composition of the marine sponge Biemna laboutei collected in the North coast of Madagascar, and the antibacterial activity of steroid mixture against human pathogenic strains. Methods: Sponge was extracted in CHCl₃/MeOH. Free steroids were separated from other lipids by column chromatography with dichloromethane as specific eluent. Free sterols/steroids and sterol acetates were analysed by gas chromatography coupled with mass spectrometry. Antibacterial activity of steroid fractions was assessed for eight strains using agar diffusion with cellulose disks. Results: Neutral lipids were the major lipid class (79.1% of total lipids). The dichloromethane eluted fraction contained only free steroids giving rise to the identification of eleven compounds. These components presented exclusively Δ7 unsaturation, including lathosterol as the major one (38.4%) and four 3-oxo-steroids (11.8%). The steroid fraction of B. laboutei has exhibited inhibitory activity against pathogenic strains but more particularly against gram(+) Bacillus cereus (MIC of 12.5 μg/mL) and Staphylococcus aureus (MIC of 25 μg/mL) strains. This latter bacterium causes several illnesses, some of those strains being antibiotic-resistant and this becomes a worldwide health problem. Conclusion: This is the first report for an antibacterial activity of a mixture of Δ7 steroids against a resistant strain of S. aureus to many antibiotics.

The most common sterol in fungi is ergosterol, which has frequently been investigated in human pathogenic fungal strains. This sterol, and others isolated from fungal strains, has also demonstrated cytotoxicity against cancer cell lines and antimicrobial activities. Marine fungi can produce high amounts of bioactive compounds. So, a screening was performed to study sterol composition using GC/MS in 19 marine fungal strains and ergosterol was always the major one. One strain, Clonostachys rosea MMS1090, was selected due to its high amount of eburicol and a one strain many compounds approach was performed on seven culture media to optimize its production. After purification and structural identification by NMR, eburicol was assessed against four cancer cell lines, MCF-7, MDA-MB-231, NSCLC-N6-L16 and A549, and seven human pathogenic bacteria Staphylococcus aureus, Bacillus sp., Bacillus cereus, Listeria ivanovii, Escherichia coli, Citrobacter freundii and Salmonella spp. The most significant activity was cytotoxicity against MCF-7 cells (2 µM). This is the first report of such an accumulation of eburicol in the marine fungal strain C. rosea confirming its potential in the production of bioactive lipids.

Diatoms adapt to changing environmental conditions in very efficient ways. Among the mechanisms that can be activated, the reorientation of carbon metabolism is crucial because it allows the storage of energy into energy-dense molecules, typically lipids. Beside their roles in physiology, lipids are commercially interesting compounds. Therefore studies dealing with this topic are relevant for both basic and applied science. Although the molecular mechanisms involved in the reorientation of carbon metabolism as a response to a deficiency in nutrients such as nitrogen or phosphorus has been partially elucidated, the impacts of carbon availability on the implementation of the reorientation mechanisms remain unclear. Indeed, it has not been determined if the same types of mechanisms are activated under carbon and other nutrient deficiencies or limitations. The first aim of this work was to get insights into the physiological, biological and molecular processes triggered by progressive carbon starvation in the model diatom Phaeodactylum tricornutum. The second aim was to investigate the effects of the growth light intensity on these processes. For such a purpose three different photon flux densities 30, 300, and 1000 μmol photons m^-2 s^-1 were used. The results presented here demonstrate that under carbon limitation, diatom cells still reorient carbon metabolism toward either phosphoenolpyruvate or pyruvate, which serves as a hub for the production of more complex molecules. The distribution of carbon atoms between the different pathways was partially affected by the growth photon flux density because low light (LL) provides conditions for the accumulation of chrysolaminarin, while medium light mostly stimulated lipid synthesis. A significant increase in the amount of proteins was observed under high light (HL).

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.