In this study, the biosurfactant produced by Pseudomonas aeruginosa was evaluated in view of its ability to be used in Microbial-Enhanced Oil Recovery (MEOR). This microorganism was isolated from a soil artificially contaminated with crude oil and used to produce rhamnolipid using glycerol as the carbon source. The biosurfactant efficiently reduced water surface tension from 72 to 35.26 mN/m at its critical micelle concentration of 127 mg/L and emulsification rate (E 24) of 69% for the crude oil. Furthermore, it was demonstrated that the rhamnolipid can recover oil, even 2 months after its production, which shows that its biodegradability is not a disadvantage to the application in MEOR. The best result, for a biosurfactant concentration of 100% above the Critical Micelle Concentration (CMC) and petroleum with API gravity of 21.90, showed that the total recovery factor was 50.45 ± 0.79%, of which 11.91 ± 0.39% corresponds to MEOR.

Biosurfactants are surfactants biologically produced by microorganisms, presenting several advantages when compared to synthetic surfactants. Pseudomonas aeruginosa is known for producing rhamnolipids, considered one of the most interesting types of biosurfactants due to their high yields, when compared to other types. In this work, the production of rhamnolipid from P. aeruginosa was optimized. At first, the Plackett–Burman design was used to select most significant variables affecting the biosurfactant production yield among nine variables—carbon–nitrogen ratio, carbon concentration, nitrogen source, pH, cultivation time, potassium and magnesium concentrations, agitation, and temperature. Then, using main variables, a central point experimental design aiming to optimize rhamnolipid production was performed. The maximum biosurfactant concentration obtained was 0.877 mg L−1. The rhamnolipid also displayed a great emulsification rate, reaching approximately 67%, and the ability to reduce water surface tension from 72.02 to 35.26 mN m−1 at a critical micelle concentration (CMC) of 127 mg L−1, in addition to presenting a good stability when exposed to wide pH and salinity ranges. The results suggest that rhamnolipids are promising substitutes for synthetic surfactants, especially due to lower impacts on the environment.

Water contamination by monoaromatic compounds has risen throughout time, which leads to the necessity of developing new water treatment technology, capable of minimizing their negative effect on the environment. In this context, biological processes present themselves as a solution to the processes of extraction. Bioremediation makes use of microbial groups capable of using hydrocarbons as a source of carbon to perform their metabolic functions. This work evaluated the biodegradation efficiency of Pseudomonas aeruginosa strain isolated from contaminated matrices, for the substrates benzene, ethylbenzene and toluene, aiming to determine to which compound the bacteria had better adaptation. For that, bioremediation assays were performed for each of the monoaromatic compounds, in an isolated way, with the goal of obtaining experimental data and from this Monod and Andrews kinetic models were discretized and numerically developed through the Runge-Kutta method. It was possible to observe that Pseudomonas aeruginosa has a bigger affinity for ethylbenzene, while benzene generated a bigger microbian coefficient. Monod´s model was capable of predicting satisfactorily the experimental data.

Biosurfactants are employed in several industrial applications which require a high purity level. However, the downstream purification processes are responsible for a large portion of the expenses incurred by biosurfactant production plants. The high costs associated with these processes turn their application on a large scale a challenge for companies. This study aimed to evaluate the influence of the purification step on the capacity of the rhamnolipid produced by a Pseudomonas aeruginosa strain to recover oil. Both purified and non-purified biosurfactants were efficient in their ability to recover oil. The best result, for the API gravity oil of 27.67, presented a total Recovery Factor of 47.45±1.78%, in which 10.2±0.85% corresponds to the MEOR. However, the results show that non-purified biosurfactant was more efficient in terms of amount of oil recovered during the MEOR stage. This demonstrates that the purification step may not be necessary, reducing the production costs of the rhamnolipid.

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