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Extraction, characterization and biological effects of polysaccharides from marine (micro)algae

PhD ceremony:Ms T. Moro
When:January 10, 2022
Start:14:30
Supervisors:A.M. (Amalia M.) Dolga, Prof Dr, prof. dr. M.D. Noseda
Co-supervisors:dr. M.E. Duarte-Noseda, dr. S.M. Brochado-Winnischofer
Where:Academy building RUG
Faculty:Science and Engineering

Polysaccharides purified from marine algae have high biotechnological value and exhibit various biological actions including cytotoxic activity, antiviral, and anticoagulant, among others. In this thesis, various polysaccharides were isolated from marine algae and microalgae, characterized and chemically modified to improve their potential biological effects. The main aim of the thesis was to characterize their chemical structures and link them to potential biological effects. Pavlova lutheri and gyrans-related β‐D-glucans showed adhesion activity with S. Typhimurium. β‐D-glucan purified from Conticribra weissflogii enhanced phagocytic activity of macrophages. Several polysaccharides purified from Isochrysis galbana induced a reduction of the mitochondrial metabolism at the level of glycolysis, the citric cycle, amino acid, and fatty acid oxidation and reduced the overall metabolic activity of U251 glioblastoma cells. Recent data showed a cytotoxic effect of U87MG cells in response to polysaccharides and corresponding oversulfated heterorhamman purified from Gayralia brasiliensis. In this thesis, we further investigated the effects of these polysaccharides on mitochondrial functions. We observed mitochondrial membrane polarization and increased mitochondrial ROS production in response to these polpolysaccharide'splication. In conclusion, polysaccharides exert various biological effects in tumor cells, and these effects vary from cell death to mitochondrial metabolism depending on the biological model, the chemical native structure or induced structural modification. For further studies, it would be worth investigating the molecular pathways of polysaccharides in relation to receptor binding and downstream protein regulation.