Aims:  Pseudomonas aeruginosa LBI (Industrial Biotechnology Laboratory) was isolated from hydrocarbon‐contaminated soil as a potential producer of biosurfactant and evaluated for hydrocarbon biodegradation. The emulsifying power and stability of the product was assessed in the laboratory, simulating water contamination with benzene, toluene, kerosene, diesel oil and crude oil at various concentrations. Methods and Results:  Bacteria were grown at 30°C and shaken at 200 rpm for 168 h, with three repetitions. Surface tension, pH and biosurfactant stability were observed in the cell‐free broth after 168 h of incubation. The strain was able to produce biosurfactant and grow in all the carbon sources under study, except benzene and toluene. When cultivated in 30% (w/v) diesel oil, the strain produced the highest quantities (9·9 g l−1) of biosurfactant. The biosurfactant was capable of emulsifying all the hydrocarbons tested. Conclusion:  The results from the present study demonstrate that Ps. aeruginosa LBI can grow in diesel oil, kerosene, crude oil and oil sludge and the biosurfactant produced has potential applications in the bioremediation of hydrocarbon‐contaminated sites. Significance and Impact of the Study:  Pseudomonas aeruginosa LBI or the biosurfactant it produces can be used in the bioremediation of environmental pollution induced by industrial discharge or accidental hydrocarbon spills.

This work aimed to evaluate the capability of different microorganisms to degrade commercial diesel oil in comparison to a weathered diesel oil collected from the groundwater at a petrol station. Two microbiological methods were used for the biodegradability assessment: the technique based on the redox indicator 2,6 -dichlorophenol indophenol (DCPIP) and soil respirometric experiments using biometer flasks. In the former we tested the bacterial cultures Staphylococcus hominis, Kocuria palustris, Pseudomonas aeruginosa LBI, Ochrobactrum anthropi and Bacillus cereus, a commercial inoculum, consortia obtained from soil and groundwater contaminated with hydrocarbons and a consortium from an uncontaminated area. In the respirometric experiments it was evaluated the capability of the native microorganisms present in the soil from a petrol station to biodegrade the diesel oils. The redox indicator experiments showed that only the consortia, even that from an uncontaminated area, were able to biodegrade the weathered diesel. In 48 days, the removal of the total petroleum hydrocarbons (TPH) in the respirometric experiments was approximately 2.5 times greater when the commercial diesel oil was used. This difference was caused by the consumption of labile hydrocarbons, present in greater quantities in the commercial diesel oil, as demonstrated by gas chromatographic analyses. Thus, results indicate that biodegradability studies that do not consider the weathering effect of the pollutants may over estimate biodegradation rates and when the bioaugmentation is necessary, the best strategy would be that one based on injection of consortia, because even cultures with recognised capability of biodegrading hydrocarbons may fail when applied isolated.

This work aimed to investigate the capability of biosurfactant production by Staphylococcus hominis, Kocuria palustris and Pseudomonas aeruginosa LBI, using weathered diesel oil from a long-standing spillage as raw material. The effect of the culture media (Robert or Bushnell-Haas) and of the carbon source (spilled diesel oil or commercial diesel oil) on biosurfactant production was evaluated. Erlenmeyer flasks (250 mL) containing the cell broth were agitated (240 rpm) for 144 h at 27±2ºC. Biosurfactant production was monitored according to the De Nöuy ring method using a Krüss K6 tensiometer. Considering the possibility of intracellular storage of biosurfactant in the cell wall of the cultures S. hominis and K. palustris, experiments were also done applying ultrasound as a way to rupture the cells. For the conditions studied, the cultures did not indicate production of biosurfactants. Results obtained with a hydrocarbon biodegradability test based on the redox indicator 2,6-dichlorophenol indophenol showed that only the commercial diesel was biodegraded by the cultures

This work investigated the efficiency of the bioaugmentation technique when applied to diesel oil contaminated soils collected at three service stations. Batch biodegradation experiments were carried out in Bartha biometer flasks (250 mL) used to measure the microbial CO 2 production. Biodegradation efficiency was also measured by quantifying the concentration of hydrocarbons. In addition to the biodegradation experiments, the capability of the studied cultures and the native microorganisms to biodegrade the diesel oil purchased from a local service station, was verified using a technique based on the redox indicator 2,6 -dichlorophenol indophenol (DCPIP). Results obtained with this test showed that the inocula used in the biodegradation