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Ion-exchange chromatography of the biologically active extracellular biopolymer produced by D. chlorelloides yielded ten fractions differing in yield, protein content, monosaccharide composition and molecular weight distribution. Their sugar compositional analyses showed rhamnogalactans, substituted to different extent by mannose and glucose, as a dominant EPS component in all fractions (91 %) except one containing arabinogalactan (7 %). In highly branched rhamnogalactans the quantity of linear (1,3-; 1,4- and 1,6-linked) and branched β-D-galactose units (1,3,6-, 1,4,6- and 1,3,4,6-linked) was nearly equal. From various α-L-rhamnose linkages the 1,2,4-linkage was dominant. Data indicate a rhamnogalactan backbone of EPS, branched by terminal mannose and glucose units, and a lot of O-methylated derivatives of galactose residues (2-O-methyl, 2,3-O-dimethyl, 3-O-methyl and 6-O-methyl). In individual fractions their content and type varied. Detail study of the arabinogalactan showed that its backbone consists of 1,3-linked β-D-Galp units; some of them are branched through O-4 by 6-OMe-α-D-Galp- (1 → 2) -α-L-Araf side chain, other through O-6 by 3-OMe-β-D-Galp, 6-OMe-β-D-Galp, β-D-Galp and β-D-Galf., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Many microalgal species produce a wide range of highly-value products which are interesting for biotechnological applications. Cultivation of microalgal species Dictyosphaerium pulchellum and Dictyosphaerium tetrachotomum, strains Růžicka and Fott resulted yields of 0.2, 0.7 and 1.8 g/L of extracellular biopolymers (EPSs), respectively. All biopolymers were shown to be anionic proteoglycans. The sugar composition analyses of all EPSs showed high contents of hexoses and the presence of partially methylated monosaccharide residues, i.e. hexoses, and deoxy hexoses. The dominant sugar component of all EPSs was found to be galactose. Extracellular microalgal biopolymers were subjected to immunobiological and immunotoxicological evaluation using murine melanoma cancer cells B16, murine fibroblast cell line NIH-3T3, murine macrophages cell line RAW 264.7 and skin construct EpiDerm™ (EPI-200). The EPSs exerted the antiproliferative effectivity; treatment of EPS induced proinflammatory cytokines TNF-α, IL-6, IL-12, IL-1β and IL-17, also engaged in anti-cancer immunity. Immunotoxicological studies revealed their non-toxic character and safe application on EpiDerm™., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Microalgae occupy all territories and their products represent a rich source of phytochemicals for human being. Green microalga Dictyosphaerium chlorelloides was found to be a significant producer of the extracellular biopolymer. Dominant components of the biopolymer were found to be Gal (39 wt%) with its methyl derivatives (15 wt%), Rha (19 wt%) and Man (14 wt%). 2-OMe-Gal was found to be the major derivative while other sugars, namely 3-OMe-, 6-OMe- and 2,3-di-OMe-Gal, 3-OMe-Glc and 4-OMe-Xyl were in smaller amounts. NMR spectroscopy revealed complex structure with galactan backbone branched by sugars in furano and pyrano forms in alpha and beta configurations. NMR data of 2-OMe, 3-OMe, 2,3-OMe and 6-OMe galactoses afforded characteristic values for O-methyls in each position. Biopolymer antitussive effect was similar to that of centrally acting antitussive drugs, indicating its relatively good antitussive potential., (Copyright © 2018 Elsevier Ltd. All rights reserved.)