Production and biotechnological potentialities of extracellular polymeric substances from sponge-associated Antarctic bacteria

Antarctic biological matrices have been never employed for the investigation of extracellular polymeric substance (EPS) production by the associated cold-adapted bacteria, even if their biotechnological potential is very wide, and comprises a lot of advantages rather than synthetic molecules. Four sponge-associated Antarctic bacteria (i.e. Winogradskyella spp. CAL384 and CAL396, Colwellia sp. GW185 and Shewanella sp. CAL606) were selected for their highly mucous aspect to investigate the enhancement of EPS production varying the carbon source, substrate, NaCl concentrations, temperature and pH values. Incubation at 4°C, 2% sucrose and 3% NaCl concentration in the medium, and pH 7 were determined as optimal conditions. EPSs were extracted in the phase of maximum production, allowing to a total amount of lyophilized exoproduct ranging from 34 to 130 mg/l. The chemical characterization of EPSs produced under optimal conditions resulted in a moderate carbohydrate content (range 15-28%), and the presence of proteins (range 3-24%) and uronic acids (range 3.2-11.9%). The chemical hydrolysis revealed galactose, glucose, galactosammine and mannose as principal constituents, with different sugar ratio for each strain. The investigation on their biotechnological potential showed an excellent emulsifying activity towards hydrocarbons by EPSs from Winogradskyella sp. CAL384, probably due to the high protein content. Moreover, EPSs showed the ability to protect cells from freeze-thaw and chelate heavy metals, probably related to the presence of uronic acids and sulfate groups. These findings suggest a possible EPS exploitation as cryoprotection agents, and the potential applications in cosmetic and food biotechnological fields as valid alternative to commercial polymers currently in use.