Techno-Functional Properties of Crude Extracts from the Green Microalga Tetraselmis suecica

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Downstream processing of Isochrysis galbana: a step towards microalgal biorefinery

An algae-based biorefinery relies on the efficient use of algae biomass through its fractionation of several valuable/bioactive compounds that can be used in industry. If this biorefinery includes green platforms as downstream processing technologies able to fulfill the requirements of green chemistry, it will end-up with sustainable processes. In the present study, a downstream processing platform has been developed to extract bioactive compounds from the microalga Isochrysis galbana using various pressurized green solvents. Extractions were performed in four sequential steps using (1) supercritical CO2 (ScCO2), (2) ScCO2/ethanol (Gas Expanded Liquid, GXL), (3) pure ethanol, and (4) pure water as solvents, respectively. The residue of the extraction step was used as the raw material for the next extraction. Optimization of the ScCO2 extraction was performed by factorial design in order to maximize carotenoid extraction. During the second step, different percentages of ethanol were evaluated (15%, 45% and 75%) in order to maximize the extraction yield of fucoxanthin, the main carotenoid present in this alga; the extraction of polar lipids was also an aim. The third and fourth steps were performed with the objective of recovering fractions with high antioxidant activity, eventually rich in carbohydrates and proteins. The green downstream platform developed in this study produced different extracts with potential for application in the food, pharmaceutical and cosmetic industries. Therefore, a good approach for complete revalorization of the microalgae biomass is proposed, by using processes complying with the green chemistry principlesThe authors acknowledge funding from the EU MIRACLES project (7th Framework Program - Grant Agreement No. 613588). B.G.L. thanks MINECO (Ministerio de Economía y Competitividad) for her Juan de la Cierva postdoctoral research contract. M.H. thanks MINECO for his Ramón y Cajal postdoctoral research contract

Bleeding disease of horse chestnut and biogenesis of a structural barrier after wounding.

<p>(A) Typical symptoms of <i>P. syringae</i> pv. <i>aesculi</i> associated bleeding disease observed on the trunk of an <i>A. carnea</i> tree, including bleeding of amber coloured sap and cracking of the bark (arrowheads). Photo taken in Sept. 2008 at N51° 57′ 26″; E5° 34′ 10″. (B) Appearance of surface wounds on <i>A. hippocastanum</i> seedlings mock-inoculated (top panel) or inoculated with <i>P. s.</i> pv. <i>aesculi</i> PD5126 (bottom panel) after 3 months. While the seedling bark recovers when mock-inoculated by regeneration of periderm, the wounded tissue appears blackened and sunken when inoculated with <i>P. s.</i> pv. <i>aesculi</i>. (C) Immunofluorescent labelling of a transverse section of the wound area sampled directly after inoculation of <i>P. s.</i> pv. <i>aesculi</i> PD4818 (t = 0) indicates that the bacteria (green) only colonize the outermost cell layer after inoculation. The scale bar indicates 100 µm. (D) A longitudinal section of a mock-inoculated wound sampled after 6 days with phloroglucinol-HCl stained lignin (red/purple). A barrier zone composed of several lignified parenchyma cells wide is visible along the wound (arrowhead) along with a broad layer of diffusely lignified cells in the disjointed part (arrow). The scale bar indicates 0.5 mm. (E) Fluorescence microscopic observation on a longitudinal section of a wound sampled 8 days after PD4818 inoculation stained for waxes using Sudan IV. The cells that exhibit lignification, as seen by the yellow/green autofluorescence, also show Sudan IV stained suberin lamellae that appear in dim red. The arrow reflects the direction of the original inoculation cut. The scale bar indicates 50 µm. (F) Detail of E showing the even deposition of suberin around the plant protoplasts. The scale bar indicates 25 µm. (G) Continuous deposition of suberin by two cells at pit fields (arrowheads). The scale bar indicates 10 µm.</p

Effect of heat-treatment on recovery of bacteria from lesions in inoculated <i>A. hippocastanum</i> saplings.

a<p>The figures are given as number of successful re-isolations per no. of lesions assessed.</p

Behaviour of GFP-expressing <i>P. syringae in planta.</i>

<p>(A) An <i>A. hippocastanum</i> seedling inoculated with strain PD4818-pMP4655 photographed after 2 months shows vertical lesion expansion (up to 6 cm in length) and tissue necrosis after removal of the outer tissues of the bark. The inoculation site is indicated with an arrowhead. Note the bending of the infection around the lower node. The scale bar indicates 1 cm. (B) Side view of a longitudinally split piece of stem from a PD4818-pMP4655 inoculated seedling removed 1–2 cm from the inoculation site 4 weeks after inoculation. Necrosis and discolouration is visible in the cambial and phloem areas. (C) A longitudinal section of an infection border in bark tissue after inoculation with PD4818-pMP4655 sampled 4 weeks after inoculation. A parabolic shaped zone with elevated cell wall autofluorescence is discernible (arrowheads) with a <i>P. s.</i> pv. <i>aesculi</i> colony located in the tip of the infected zone, at about 1 cm away from the inoculation site. The boxed area is shown in detail in D. The scale bar indicates 25 µm. (D) Numerous bacteria are clustered near the forefront of an advancing lesion in parenchyma 4 weeks after inoculation. The bacteria observed here are relatively small and densely packed. The scale bar indicates 10 µm. (E) Within the necrotic area near the original site of inoculation several clusters of bacteria are found that occupy the cavities left by dead cells. Image taken from a longitudinal section of a 6 week old infection. The scale bar indicates 25 µm. (F) A large aggregate of PD4818-pMP4655 located in necrotic tissue of a 4 week old lesion. Individual bacteria were spaced apart and did not undergo any type of motility. The scale bar indicates 25 µm. (G) Detail of a PD4818-pMP4655 cluster in necrotic tissue of a 4 week old infection, emphasizing the spacing between individual bacteria. The scale bar indicates 10 µm. (H) Immunodetection of wild-type PD4818 in the necrotic tissue of a 10 week old infection showing a similar spatial arrangement of bacteria to that shown in G. The scale bar indicates 10 µm.</p