Monitoramento da produção de biossurfactantes durante o crescimento de Bacillus paralicheniformis em batelada

Abstract

Oil is one of the most important energy resources ever explored by man. Despite the socioeconomic and ecological complications associated to its extraction, its exploitation does not show signs of deceleration and many studies are directed to the extraction techniques to improve and guarantee its production. Among them, the improved recovery of oil using microorganisms (MEOR) has been mainly focused on its efficiency, economy and ecological safety when compared to other extraction improvement techniques. Bacteria belonging to the genus Bacillus are known to produce biosurfactant molecules belonging to the class of lipopeptides. With low molecular weight, lipopeptides are among the most efficient surfactants in reducing surface tension and interfacial, essential phenomena in MEOR. The present work analyzed the production of biosurfactants in batch by a strain of Bacillus isolated from mangrove sediments, in order to isolate and identify those with the greatest potential for application in MEOR. The bacteria were grown in mineral medium having glucose as carbon source and the production of biosurfactants was monitored by means of oil dispersing activity, emulsifying activity and the measurement of surface tension. The results showed that culture supernatants were able to disperse spilled oil into sea water, indicating the presence of surfactants. Only ICA58 showed no emulsifying activity, undesired activity in MEOR, so this strain was selected for further testing and identification. Molecular identification based on the 16S, gyrB and rpoB rRNA genes showed that ICA58 is phylogenetically related to the Bacillus paralicheniformis species. The surfactant produced by ICA58 reduced the surface tension of water to 27.7 mN/m. The bacterium produced surfactant in NaCl concentration of 50 mg/L. The surfactant produced is resistant to autoclaving (121 ° C, 15 min) and high salinity (200 g/L NaCl). After autoclaving, ICA58 surfactant showed emulsifying activity, suggesting that this activity was inhibited by some de-emulsifying agent. Taken together, these results suggest that ICA58 produces more than one lipopeptide class and / or isoform and that the molecules of interest can be obtained at different times of cultivation and that all activities detected have potential for applications in the petroleum industry, MEOR.