Production and Biotechnological Potential of Extracellular Polymeric Substances from Sponge-Associated Antarctic Bacteria

• Published in: Applied and Environmental Microbiology
• Main Authors: Caruso, Consolazione, Rizzo, Carmen, Mangano, Santina, Poli, Annarita, Di Donato, Paola, Finore, Ilaria, Nicolaus, Barbara, Di Marco, Gaetano, Michaud, Luigi, Lo Giudice, Angelina
• Format: Text
• Language: English
• Published: American Society for Microbiology 2018
• Subjects: Biotechnology; Antarctic; Antarc*
• Online Access: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5795064/; http://www.ncbi.nlm.nih.gov/pubmed/29180360; https://doi.org/10.1128/AEM.01624-17

Four sponge-associated Antarctic bacteria (i.e., Winogradskyella sp. strains CAL384 and CAL396, Colwellia sp. strain GW185, and Shewanella sp. strain CAL606) were selected for the highly mucous appearance of their colonies on agar plates. The production of extracellular polymeric substances (EPSs) was enhanced by a step-by-step approach, varying the carbon source, substrate and NaCl concentrations, temperature, and pH. The EPSs produced under optimal conditions were chemically characterized, resulting in a moderate carbohydrate content (range, 15 to 28%) and the presence of proteins (range, 3 to 24%) and uronic acids (range, 3.2 to 11.9%). Chemical hydrolysis of the carbohydrate portion revealed galactose, glucose, galactosamine, and mannose as the principal constituents. The potential biotechnological applications of the EPSs were also investigated. The high protein content in the EPSs from Winogradskyella sp. CAL384 was probably responsible for the excellent emulsifying activity toward tested hydrocarbons, with a stable emulsification index (E24) higher than those recorded for synthetic surfactants. All the EPSs tested in this work improved the freeze-thaw survival ratio of the isolates, suggesting that they may be exploited as cryoprotection agents. The addition of a sugar in the culture medium, by stimulating EPS production, also allowed isolates to grow in the presence of higher concentrations of mercury and cadmium. This finding was probably dependent on the presence of uronic acids and sulfate groups, which can act as ligands for cations, in the extracted EPSs.