Abstract
A novel bacterial strain of Pseudomonas aeruginosa has been isolated and characterized by screening samples from formation water of local oil wells and other habitat, which overproduced potent biosurfactant under phosphate limiting condition within 36 hours of incubation. Biosurfactant producing bacteria were isolated from the oil, formation water and from the soil contaminated with oil from the local oil wells; strains were grown on different medias having different carbon sources. Selected 66% culture reduced surface tension lesser than 33 mN/m and interfacial tension lesser than 3 mN/m whereas 85% showed hemolytic activity. Pseudomonas spp. was most common while some Micrococcus and Acinetobacter were also identified. Most potent biosurfactant producers were P. aeruginosa, P. fluorescens and Micrococcus spp. P. aeruginosa strain GW-7 was selected for further studies. BHmineral medium was best for biosurfactant production as it reduced surface tension to (32 mN/m), interfacial tension (2.5 mN/m).Other best medium was an inorganic phosphate limited medium containing proteose peptone/glucose/ ammonium salts, as its surface tension and interfacial tension reached to 30 mN/m and 2.5 mN/ m, respectively, after 36 hours. P. aeruginosa isolate GW-7 isolated from oil enriched soils from Gwadar coastal area produced potent biosurfactant (rhamnolipid) in large amount in reasonably short period of time (36 hours) under nitrogen and phosphate limiting conditions
