The red microalga Flintiella sanguinaria as a new exopolysaccharide producer

Flintiella sanguinaria is a red unicellular microalgae belonging to Porphyridiophyceae with a high potential as an exopolysaccharide producer. A new culture medium was developed by a stoichiometry approach based on elemental analysis of microalgae, and culture conditions were improved after measurements of photosynthetic activity as a function of irradiance, temperature and pH. These optimal conditions were thus validated in a photobioreactor for the production of biomass and exopolysaccharide (EPS). After extraction and purification of the EPS, it was characterised by HPAEC-PAD, HPLC and FT-IR as a methylated and acetylated galactoxylan including a significant amount of rhamnose and glucuronic acid in its structure. Macromolecular conformation in dilute solution of native, deproteinised and desubstituted EPS from F. sanguinaria revealed that this polysaccharide had a strong associative behaviour in which hydrophobic interactions or hydrogen bonding but also proteins were implicated.