Biodegradation of a bioemulsificant exopolysaccharide (EPS2003) by marine bacteria.

The aim of the study is to analyze the biodegradation capacity of a biosurfactant exopolysaccharide (EPS2003) by heterotrophic marine bacterial strains. During the initial screening performed in two sites located at the harbor of Messina for analyzing the response of marine bacterial population with the presence of biosurfactant EPS2003, ten bacterial strains capable to degrade this substance were isolated. Between the bacterial strains isolated, two representative bacterial strains, isoDES-01, clustered with Pseudoalteromonas sp. A28 (100%), and isoDES-07, closely related to Vibrio proteolyticus (98.9%), were chosen for mineralization and respirometry test, performed to evaluate biodegradability potential of EPS2003. Assays of bacterial growth and measure of concentration of total RNA were also performed. More than 90% of EPS2003 was mineralized by the isoDE01 strain for biomass formation and respiration, while EPS2003 mineralization by the isoDE-07 strain was less effective, reaching 60%. This approach combines the study of the microbial community with its functional aspects (i.e., mineralization and respirometry test) allowing a more precise assessment of biosurfactant degradation. These results enhance our knowledge of microbial ecology of EPS-degrading bacteria and the mechanisms by which this biodegradation occurs. This will prove helpful for predicting the environmental fate of these compounds and for developing practical EPS2003 bioremediation strategies from future marine hydrocarbon pollution.