Marine benthic diatoms : an original ressource of « oleaginous » strains for health and nutrition

Les diatomées marines benthiques représentent à ce jour un vivier sous-exploité et constituent donc une ressource potentielle pour la valorisation de lipides d’intérêt en santé et nutrition. Dans ce cadre, après un criblage réalisé sur plus d’une centaine de souches de la collection régionale NCC, six espèces : Amphora sp. NCC169., Entomoneis paludosa NCC18.2, Nitzschia sp. NCC109, Nitzschia alexandrina NCC33, Opephora sp. NCC366 et Staurosira sp. NCC182 ont été retenues sur la base de leurs productions lipidiques et de leur capacité de croissance. Ces six espèces ont ensuite été produites en photo-bioréacteur airlift pour établir leur capacité de croissance et de production lipidique. Une étude lipidique approfondie a également été menée à la fois sur les lipides neutres (TAG, stérols) et les lipides polaires (glycolipides, phospholipides) afin d’évaluer leur potentiel en matière de diversité lipidique et de production de lipides d’intérêt. Trois espèces ont été sélectionnées (E. paludosa, N. Alexandrina et Staurosira sp.) pour évaluer le potentiel bio actif des fractions lipidiques extraites. Il a été démontré que les fractions glycolipidiques possèdent une activité antiproliférative sur les lignées cancéreuse MC-F7 (sein) et NSCLC-N6 (poumon) ainsi qu’une activité antibactérienne sur les souches de bactéries à gram-positif (B. subtillus). Enfin l’étude de l’impact des conditions de cultures (lumière et azote) sur la qualité des acides gras produits a démontré que pour optimiser la production de lipides d’intérêt un milieu non-limitant et une faible intensité lumineuse devraient être utilisés pour une production à grande échelle.Marine benthic diatoms represent an under-exploited pool and therefore constitue a potential resource for the valorization of lipids of interest in heath and nutrition. In this framework, after a screening of more than one hundred strains from the NCC regional collection, six species : Amphora sp. NCC169., Entomoneis paludosa NCC18.2, Nitzschia sp. NCC109, Nitzschia alexandrina NCC33, Opephora sp. NCC366 et Staurosira sp. NCC182 have been selected on the basis of their lipid production and growth capacity. These six species were then produced in airlift photobioreactor to establish their capacity for growth and lipid production. A thorough lipid study was also conducted on both neutral lipids (TAG, sterols) and polar lipids (glycolipids, phospholipids) to evaluate their potential for lipid diversity and lipid production of interest. Three species (E. paludosa, N. Alexandrina et Staurosira sp.) have been selected to evaluate the bioactive potential of extracted lipid fractions. The glycolipids fractions shown antiproliferative activity on the MCF-7 (breast) and NSCLC-N6 (lung) cancer cell lines as an antibacterial activity on gram-positive bacterial strains (B. subtillus). Finally, this study demonstrated the impact of culture conditions (light and nitrogen) on the fatty acids quality. To optimize the production of lipids of interest a non-limiting medium and low light intensity should be used for large scale production

Exploration of the bioactive lipids diversity of the marine benthic diatoms of the Nantes Culture Collection (NCC)

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Lipids in benthic diatoms: A new suitable screening procedure

The selection of suitable and indigenous microalgae species is a fundamental requirement in developing added-value bioactive compounds recoverable in the food, health, and cosmetics markets. In this work, an integrated screening approach was developed to characterize the lipid rate of 33 diatom species (including 15 species studied for the first time) belonging to 16 genera from the Nantes Culture Collection, with the main objective of discovering bioactive lipid producers. For that purpose, a simple reliable method for establishing growth kinetics of strains and semi-quantitative analysis of lipid rates was developed. Growth kinetics measurements were achieved by daily minimal measurement fluorescence (F0) whereas lipid rate analyses were performed by high-throughput Fourier Transform Infrared spectroscopy on entire cells and lipid extracts. Results indicated that the method could be used directly on entire cells in spite of the presence of silica for the FTIR approach (due to frustule). The total lipid rate was species-dependant and ranged from 3.7% to 30.5% DW. Six strains out of 33 were found to present a higher total lipid rate superior to 15% DW, and 11 showed medium lipid rates ranging from 10% to 15% DW. The results revealed that five diatom species i.e. Amphora sp. NCC169, Nitzschia sp. NCC109, Nitzschia alexandrina NCC33, Opephora sp. NCC366 and Staurosira sp. NCC182 presented interesting growth capabilities and should be further investigated as potential sources for their original lipid rate

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

LIPID ANALYSIS OF SIX DIATOMS SPECIES FROM THE NANTES CULTURE COLLECTION

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