Biodegradative potential and characterization of bioemulsifiers of marine bacteria isolated from samples of seawater, sediment and fuel extracted at 4000 m of depth (Prestige wreck)

Seawater, sediments and fuel samples extracted from a small area of the Prestige wreck (4000 m deep) were studied to check the microbial activity of the area, the occurrence of indigenous hydrocarbon-degrading bacteria and the presence of bacteria able to produce bioemulsifiers. Twenty-one strains with the capacity to degrade hydrocarbons and/or produce useful bioemulsifiers were selected. Phylogenetic affiliation of these isolates placed them in the genus Bacillus (8 strains), Pseudomonas (3 strains), Halomonas (4 strains), Pseudoalteromonas (1 strain), Brevibacterium (2 strains), and Marinobacter (1 strain) and 2 strains were identified as marine bacterium. Hydrocarbon degradation was established by determining the amount of alkanes and polycyclic aromatic hydrocarbons by GC/MS analyses. In this study, Pseudomonas, Bacillus and Brevibacterium strains were the most efficient hydrocarbon-degrading marine bacteria. In contrast, Halomonas strains produced the highest amount of efficient biopolymers with emulsifying activity. The yield, chemical composition and functional properties of these bioemulsifiers were affected by the incubation time required for production. In addition, supplementation of the hydrocarbon culture medium with bioemulsifiers (S22-BE, S24-BE and AD2-BE) clearly stimulated the growth of strains S25, S28 and S29 and enhanced the ability of these strains to biodegrade alkanes, alkenes and aromatic compounds.