Affiliation:
1. Department of Chemical, Biological and Pharmaceutical Environmental Sciences (ChiBioFarAm), University of Messina, Messina, Italy
2. Institute of Biomolecular Chemistry, National Research Council (ICB-CNR), Pozzuoli (NA), Italy
3. Department of Science and Technology, University of Naples Parthenope—Centro Direzionale, Naples, Italy
4. Institute for the Chemical-Physical Processes, National Research Council (IPCF-CNR), Messina, Italy
5. Institute for the Coastal Marine Environment, National Research Council (IAMC-CNR), Messina, Italy
Abstract
ABSTRACT
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 (E
24
) 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.
IMPORTANCE
To date, biological matrices have never been employed for the investigation of EPS production by Antarctic psychrotolerant marine bacteria. The biotechnological potential of extracellular polymeric substances produced by Antarctic bacteria is very broad and comprises many advantages, due to their biodegradability, high selectivity, and specific action compared to synthetic molecules. Here, several interesting EPS properties have been highlighted, such as emulsifying activity, cryoprotection, biofilm formation, and heavy metal chelation, suggesting their potential applications in cosmetic, environmental, and food biotechnological fields as valid alternatives to the commercial polymers currently used.
Funder
Italian Ministry of Education and Research
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology