## 1 Introduction  
Water-soluble sulfated galactans are the main constituents of the non-fibrillar cell walls and intercellular matrix of most red algae (Rhodophyta) [1; 2; 3]. They show a linear backbone consisting of alternating (1,4)-linked \(\alpha\)-Gal (and/or 3,6-\(\alpha\)-AnGal) and (1,3)-linked \(\beta\)-Gal units. The latter residue always belongs to the \(\mathsf{n}\)-series, while the former (\(\alpha\)-Gal) can occur as \(\mathsf{n}\)-(carrageenanans) or \(\mathsf{n}\)-(agarans) series [4; 5; 6; 7]. The main backbone can be substituted by pyruvate acid ketals, sulfate, \(O\)-glycosyl and/or methyl groups and also by side chains, giving rise to great structural changes along the galactan chain. These structural changes affect the physicochemical and rheological behaviors of these polymers. So far, it has been reported that sulfated galactans exhibit numerous biological properties, including antioxidant, anticoagulant, antinociceptive, immunomodulatory, anticancer, gastroprotective, anti-inflammatory, antithrombotic and antiproliferative [1; 6; 7; 8; 9; 10; 11; 12; 13; 14]. Marine seaweed (Phaeophyceae and Rhodophyceae) cell wall polysaccharides also hold great promise as a raw material for feed, food, and biofuel production. Through metabolic engineering, seaweeds (micro- and macroalgae) are attracting growing attention as an alternative source of biofuel by converting the seaweed biomass and, in particular, the cell wall, which is rich in carbohydrates, into liquid biofuels [15]. Galactans are currently used as thickening, gelling, and stabilizing agents in food, cosmetic, and pharmaceutical fields [1; 10; 11; 12; 13; 14; 15; 16]. However, sulfated galactans produced by Corallinales are less studied, probably because of their strong calcareous cover, which decreases the production yield [17]. Up until now, only six species that produce sulfated galactan from the Corallinales order (_Joculator maximus_, _Corallina pillifera_, _Corallina officinalis_, _Bossiella creetaca_, _Bossiella orbigiana_, _Jania rubens_ and _Lithothammon heterocladum_) have been reported [2; 3; 4; 18; 19; 20]. Their common structural feature is an agaran main chain in which (1,3)-\(\mathsf{B}\)-\(\mathsf{n}\)-\(\mathsf{Gal}\)\(\mathsf{n}\) residues are almost completely substituted in \(O\)-6 positions, mainly by \(\mathsf{\beta}\)-\(\mathsf{N}\)\(\mathsf{yl}\)\(\mathsf{p}\) side chains, but also by some sulfate groups. \(\alpha\)-\(\mathsf{l}\)-\(\mathsf{Gal}\)\(\mathsf{p}\) residues are also partially substituted by sulfate and methoxy groups in the \(O\)-2 position [4; 19; 20]. Some sulfate groups have also been reported on the \(O\)-3 position of the \(\alpha\)-\(\mathsf{l}\)-\(\mathsf{Gal}\)\(\mathsf{p}\) units. Note that 3,6-\(\mathsf{AnGal}\)\(\mathsf{p}\) residues were previously reported in _Jania rubens_[3]. _Jania aduarerens_ ([PERSON]) belongs to the Corallinales order and Corallinaceae algal family. This genus is widely present in the Mediterranean and Atlantic coasts and mostly found mixed with the brown alga _Cystoseira crinita_. To our knowledge, there is no data in the literature concerning some structural features and rheological properties of the polysaccharides extracted from _J. aduarerens_. Besides, this macroalgae is not used for ethnomedicine or as food by local populations. Today, Tunisia mainly imports phycocolloids and does not promote the macroalgae industry to produce agaroids at a large scale. Regarding these drawbacks and the strong ethnobotanic (endemic species) but also economic (climatic conditions, market potential in North Africa, etc.) potential of this algae, this work aimed to identify the value of _Jania aduarerens_ as a new feedstock for producing agaroids.