CONICET | Buscador de Institutos y Recursos Humanos

Hydrophobic compounds bioavailability is a key factor for their biodegradation and mobilization. Because of that, the use of surfactants was proposed as additives in Surfactant Enhanced Remediation (SER) and in Surfactant Enhanced Oil Recovery (SEOR). The use of biosurfactants instead of the synthetic ones have some environmental advantages like less toxicity and higher biodegradability, that make these biomolecules an environmentally friendly alternative. Previous studies from our group showed that Pseudomonas sp. KA-08 was able to secrete biosurfactants to the culture media when it grew in kerosene as sole carbon source and a crude extract surfactant (CES) could be obtained from a cell-free supernatant of these cultures. In this work we analyzed the surface tension lowering capabilities of the different compounds present in the CES and their chemical composition.Pseudomonas sp. KA-08 was cultured in 50 ml E2 minimum medium supplemented with 10% kerosene in 500 ml capped bottles at 280 rpm and 30°C. After 7 days, cultures were centrifuged at 3500 rpm for 20 minutes, the oil phase was removed and supernatants were acidified up to pH 2 and left overnight at 4°C. Then, they were extracted thrice with half the volume of ethyl acetate and concentrated to dryness by Rotavap to obtain the CES. To calculate its critical micelle concentration (CMC) a Du Nouy ring method was used, obtaining a CMC = 670 μg/ml ± 76 μg/ml. For better characterization of the CES components, a silica gel chromatographic column (diameter: 1,50cm, length: 40cm) was performed using solvents in increasing order of polarity as elutants, in order to separate the compounds for further analysis. The elution fractions were collected, analyzed by TLC and revealed with UV light or Molisch reagent. The fractions who showed unique spots with a conserved Rf were grouped, obtaining 4 pooled fractions. Each pool was evaporated to dryness, resuspended in bidistilled water and tested by the drop-collapse method. Three of them showed a contact angle dismitution of 10° ± 3°, 18° ± 4° and 18° ± 3° respectively. The predominant one, who showed positive for Molisch reagent ( glycosidic nature) was analyzed by 1H and 13C-NMR spectroscopy and exhibited complex spectra with aliphatic and aromatic moieties.This work allows us to continue the chemical analysis of the compound purified and to study the potential use of the CES as a biosurfactant additive in microcosms polluted with hydrocarbons.

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