Exopolysaccharide production by a marine Pseudoalteromonas sp. strain isolated from Madeira Archipelago ocean sediments

•Isolation of a Pseudoalteromonas sp. strain from Madeira Archipelago ocean sediments.•The strain presents autolytic behavior during batch cultivation.•Synthesis of EPS with high uronic acids content.•Fermentation broth develops high viscosity at the end of cultivation. Exopolysaccharides (EPS) are polymers excreted by some microorganisms with interesting properties and used in many industrial applications. A new Pseudoalteromonas sp. strain, MD12-642, was isolated from marine sediments and cultivated in bioreactor in saline culture medium containing glucose as carbon source. Its ability to produce EPS under saline conditions was demonstrated reaching an EPS production of 4.4g/L within 17hours of cultivation, corresponding to a volumetric productivity of 0.25g/Lh, the highest value so far obtained for Pseudoalteromonas sp. strains. The compositional analysis of the EPS revealed the presence of galacturonic acid (41–42mol%), glucuronic acid (25–26mol%), rhamnose (16–22mol%) and glucosamine (12–16mol%) sugar residues. The polymer presents a high molecular weight (above 1000kDa). These results encourage the biotechnological exploitation of strain MD12-642 for the production of valuable EPS with unique composition, using saline by-products/wastes as feedstocks.