The Role of Exopolysaccharide, Biosurfactant and Peroxidase Enzymes on Toluene Degradation by Bacteria Isolated From Marine and Wastewater Environments

Toluene which widely exists in petroleum and its related products has gathered much attention due to its adverse effects on health and carcinogenic potential. Since microorganisms are able to utilize petroleum hydrocarbon as carbon and energy sources, they can be used for bioremediation applications. The aim of this study was to isolate toluene degrading bacteria from wastewater and seawater. The production of exopolysaccharide, biosurfactant and peroxidase enzymes such as laccase and catalase were investigated to determine the effect of them on toluene degradation. To screen and isolate toluene degrading bacteria, contaminated seawater and wastewater samples were added to toluene containing mineral media (MM). The biochemical and molecular characteristics of the isolates were then studied. From seawater, two toluene degrading Bacillus and one Sporosacina species and from wastewater a novel high capable toluene degrading strain, Bacterium Ex-DG74 were isolated and introduced. Bacterium Ex-DG74 showed tolerance to 15 % (v/v) toluene but the marine isolated species could tolerate only 1 % (v/v) toluene. This bacterium also showed the highest catalase and membrane-bound laccase activity. The spore-forming marine bacterium, S. halophila produced large amounts of exopolysaccharide, biosurfactant and extracellular laccase. The results of the present research indicated that EPS, biosurfactant and peroxidase enzymes can have essential roles on toluene tolerance and biodegradation. These native microbial isolates could be considered as a powerful approach for the in situ bioremediation of hydrocarbon-contaminated sea and wastewater.