Screening and identification of biosurfactant producing marine bacteria from the Caspian Sea

Marine microorganisms have unique physiological properties and novel metabolites such as biosurfactant to live in extreme habitats (e.g. oil polluted environment). The aim of this study was to characterize some biosurfactant-producing bacteria collected from sediment and seawater samples from the Caspian Sea. These bacteria were isolated using enrichment method in ONR۷a medium with crude oil as sole carbon source. Five screening tests were used for selection of the bacteria including hemolysis in blood agar, oil spreading, drop collapse, emulsification activity and bacterial adhesion to hydrocarbon test (BATH). The bacteria isolated were identified using molecular methods. Eighteen biosurfactant-producing bacteria (from ۴۴ different colonies isolated) were selected and ۹ isolates were screened as predominant biosurfactant producer belonging to Pseudomonas stutzeri (Strain S۱-۴-۲), P. balearica (Strain S۱-۴-۱), Pseudomonas sp. (Strain S۲-۱), P. stutzeri (Strain R۳-۲), P. chloritidismutans (Strain K۴-۱), Achromobacter xylosoxidans (Strain K۴-۳), Acinetobacter radioresistens (Strain S۱-۲), Acinetobacter calcoaceticus (Strain K۴-۲) and Citrobacter freundii (Strain R۳-۱). The largest clear zone diameters for oil spreading method observed for P. balearica strain S۱-۴-۱ (۱۴ mm). Also, this strain has the best emulsification activity (۱۰۰ %); surface hydrophobicity (BATH: ۷۷ %) and reduction of surface tension (۳۴.۵ mN m-۱). Thus, this strain selected as the best isolated strains. The results of this study confirmed that there is sufficient diversity of biosurfactant-producing bacteria in the Caspian Sea and the environmental problem can be resolved by application of these bacteria in petrochemical waste water.

کلیدواژه ها:

Biodegradation ، Biosurfactant ، Caspian Sea ، Marine environment