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Jebali J.,Higher Institute of Agriculture | Chicano-Galvez E.,University of Cordoba, Spain | Banni M.,Higher Institute of Agriculture | Guerbej H.,National Institute of Marine science and Technology | And 3 more authors.
Ecotoxicology and Environmental Safety | Year: 2013

Gilthead seabream (Sparus aurata) specimens were caged in-field at the Téboulba harbour or exposed to benzo(a)pyrene [B(a)P] or to paraquat [PQ] plus B(a)P, and several biochemical biomarker responses were investigated. Antioxidant enzymes, such as glutathione peroxidase, catalase and glutathione reductase, significantly increased in the in-field and B(a)P+PQ exposures, but were only moderately affected by B(a)P alone. Glucose-6-phosphate and 6-phosphogluconate dehydrogenases significantly diminished after in-field exposure. Different responses with biotransformation enzymes were observed: the P4501A-associated EROD activity was highly induced in response to B(a)P and B(a)P+PQ exposures, while total activity of the glutathione S-transferase (GST) was similar to control. However, after purification of the GST proteins by affinity chromatograpy and analysis by two-dimensional electrophoresis, nineteen highly reproducible isoforms were resolved. In addition, some of reproducible isoforms showed different and specific expression patterns in response to contaminants.Thus, proteomic analysis of the purified GST subunits is a reliable tool for ecotoxicological research, useful in polluted marine ecosystem as an effective biomarker of contamination. © 2012 Elsevier Inc.

Trabelsi L.,National Institute of Marine science and Technology | Chaieb O.,National Institute of Marine science and Technology | Mnari A.,Research Laboratory in Nutrition Functional Food | Abid-Essafi S.,Laboratory of Research on Biologically Compatible Compounds | Aleya L.,University of Burgundy
BMC Complementary and Alternative Medicine | Year: 2016

Background: For thousands of years, Tunisian geothermal water has been used in bathing. Indeed, thermal baths "Hammam" were recommended in the treatment of different type of illnesses as, for instance, for relaxing joints and soothing. The ability of microalgae to sustain at the high temperature makes them potential producers of high value thermostable bio-products. This study aimed to explore the therapeutic potential of the aqueous extracellular polysaccharides (AEPS) of the Tunisian thermophilic microalgae Graesiella sp. and to evaluate its physico-chemical characteristics. Methods: Different parameters were used to characterize the AEPS. The dry weight, volatile dry weight, elemental analysis, monosaccharide composition and IR-spectroscopy analysis. Carbohydrate, uronic acid, ester sulfate and protein concentrations were also determined using colorimetric assay. AEPS was analyzed for its antioxidant propriety by means of total antioxidant capacity, DPPH radicals scavenging assay, ferrous chelating ability and hydroxyl and superoxide radical scavenging activity. The antiproliferative activity of AEPS was evaluated for HepG2 and Caco-2 cells using the MTT assay. Results: The Graesiella sp. AEPS is found to be a hetero-sulfated-anionic polysaccharides that contain carbohydrate (52 %), uronic acids (23 %), ester sulfate (11 %) and protein (12 %). The carbohydrate fraction was formed by eight neutral sugars glucose, galactose, mannose, fucose, rhamnose, xylose, arabinose and ribose. The FT-IR revealed the presence of carboxyl, hydroxyl, amine and sulfate groups. AEPS showed high activity as reducing agent, high ferrous chelating capacity and caused a significant decrease in a concentration-dependent manner of hydroxyl radical. A moderate DPPH scavenging activity and a poor superoxide radical scavenging ability were also observed. AEPS treatment (from 0.01 to 2.5 mg/ml) caused also a clear decrease of cell viabilities in a dose-dependent manner. The IC50 values obtained in HepG2 and Caco-2 cells were 1.06 mg/ml and 0.3 mg/ml respectively. Conclusions: This study evidenced that the Graesiella sp. AEPS exhibits antioxidant and antiproliferative activities. The biological activities of this extract depend on its fine structural features. Further work will identify and purify the active polysaccharides to enhance our understanding of their complete structure and relationships with its function. © 2016 The Author(s).

Zili F.,National Institute of Marine science and Technology | Mezhoud N.,National Institute of Marine science and Technology | Mezhoud N.,Masdar Institute of Science and Technology | Trabelsi L.,National Institute of Marine science and Technology | And 2 more authors.
Journal of Applied Phycology | Year: 2014

The combined effect of temperature, light intensity, and NaNO3 concentration on lipid biosynthesis and fatty acid composition was investigated for the thermophilic cyanobacterium Gloeocapsa gelatinosa (Kützing 1843) isolated from a thermal spring in Tunisia. Under optimal growth conditions, the lipid content was 7.3 % DW. Fatty acid analysis revealed the predominance of 16:0 and 18:0 (23.7 and 18.2 %, respectively) as main straight carbon chains of saturated fatty acids. Unsaturated fatty acids were also identified with 18:1n9c (18.8 %) and 16:1n7 (5 %) being the predominant components. The effect of environmental factors on fatty acid composition was monitored by using principal component analysis and central composite design. Variation of light intensity (20 to 150 μmol photons m-2 s-1), temperature (20 to 60 °C), and nitrogen concentration (0 to 3 g L-1) induced a significant variation in the amount of fatty acid proportions, whereas lipid content was only slightly modified. Results showed that light intensity had the strongest effect on the composition of fatty acids. Temperature had a synergic effect with light intensity while nitrogen concentration had a trivial effect. The combined effect of high light intensity (150 μmol photons m-2 s-1) and high temperature (60 °C) increased the proportion of saturated 16:0 and 18:0 fatty acids along with long-chain fatty acids to 82 % which was twofold higher than that in optimal growth conditions. This induced fatty acid profile makes G. gelatinosa-based biofuels adaptable for higher energetic efficiency and higher oxidative stability. © 2014 Springer Science+Business Media Dordrecht.

Fathallah S.,National Institute of Marine science and Technology | Medhioub M.N.,National Institute of Marine science and Technology | Kraiem M.M.,National Institute of Marine science and Technology
Environmental Engineering Science | Year: 2013

Individual and combined toxicities of lead (Pb) and cadmium (Cd) were investigated using sperm motility and embryo-larval bioassay of the clam Ruditapes decussatus. Fertilization and embryogenesis success and larval mortality were recorded after incubation of sperm (during 30 min before use for insemination), fertilized eggs (24 h) and D-shaped larvae (96 h) in seawater, both with single metals and combinations of the two tested metals. In spermiotoxicity bioassays, these metals, both individually and in combination, significantly (p<0.05) reduced the fertilization rate only at two higher concentrations that were studied. Median effective concentration (EC 50) values were 1033 μg/L (5 μM), 2098.5 μg/L (18.6 μM), and 1442 μg/L (10.8 μM), respectively for individual Pb, Cd, and the mixture (Pb+Cd). Embryogenesis success was also noticeably affected by the single metals and their mixture. Median effective concentrations (EC 50) values were 256.5 μg/L (1.24 μM), 570.9 μg/L (5.08 μM), and 355.4 μg/L (2.68 μM), respectively for individual Pb, Cd, and the mixture (Pb+Cd). Median lethal concentration (LC50) for 96 h larval mortality bioassay registered for individual Pb, Cd, and for the mixture were 453.6 μg/L (2.2 μM), 877.8 μg/L (7.8 μM), and 565.6 μg/L (4.3 μM), respectively. Marking-Dawson additive toxicity indices were 0.01, 0.08, and 0.18, respectively, for spermiotoxicity, embryotoxicity, and larval mortality tests, indicating additive effects with a slight trend toward synergism, which was statistically significant only for larval mortality. This work shows that both clam embryos and larvae bioassays are useful tools that can be used to evaluate toxicity of field samples of seawater, sediments, and effluents containing several toxicants. © Mary Ann Liebert, Inc.

Mezhoud N.,National Institute of Marine science and Technology | Mezhoud N.,Masdar Institute of Science and Technology | Zili F.,National Institute of Marine science and Technology | Bouzidi N.,National Institute of Marine science and Technology | And 3 more authors.
Bioprocess and Biosystems Engineering | Year: 2014

Tunisian microalgae are diverse and rarely been studied. This study reports a first investigation of thermophile Chlorophyta isolated from mats community colonizing the geothermal springs in the north of Tunisia at water temperature 60°C. In the study, the combined effect of temperature and light intensity was investigated on the cell growth, the mother and daughter cells abundance and the extracellular polymeric substances synthesis in batch culture of the isolated species. Three levels were tested for each factor, 20, 30, 40°C for temperature; and 20, 70, 120 μmol photons m-2 s-1 for light intensity, using full factorial design and response surface methodology. The thermophile strain was identified as a genus Graesiella and showed 99.8 % similarity with two Graesiella species: Graesiella emersonii and Graesiella vacuolata based on the 18S rDNA molecular identification. The optimal growth condition was found at 30°C and 120 μmol photons m-2 s-1 (7 MC mL-1 day-1), with the abundance of vegetative cells (daughter cells). In contrast, the number of mother cells increased significantly as the growth decreased; consequently, the highest ratio of auto spore mother cells versus daughter cells (19.4) was obtained at 20°C and 20 μmol photons m-2 s-1. The highest yield of EPS production (11.7 mg L-1 day-1) was recorded at the highest temperature (40°C) and lowest light intensity (20 μmol photons m-2s-1). These results revealed how the species respond to high and low temperatures and suggest that the species should be considered as facultative thermophile. © 2014 Springer-Verlag.

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