Abstract
BackgroundLipopeptides are known as promising microbial surfactants and have been successfully used in enhancing oil recovery in extreme environmental conditions. A biosurfactant-producing strain, Bacillus atrophaeus 5-2a, was recently isolated from an oil-contaminated soil in the Ansai oilfield, Northwest China. In this study, we evaluated the crude oil removal efficiency of lipopeptide biosurfactants produced by B. atrophaeus 5-2a and their feasibility for use in microbial enhanced oil recovery.ResultsThe production of biosurfactants by B. atrophaeus 5-2a was tested in culture media containing eight carbon sources and nitrogen sources. The production of a crude biosurfactant was 0.77 g L−1 and its surface tension was 26.52 ± 0.057 mN m−1 in a basal medium containing brown sugar (carbon source) and urea (nitrogen source). The biosurfactants produced by the strain 5-2a demonstrated excellent oil spreading activity and created a stable emulsion with paraffin oil. The stability of the biosurfactants was assessed under a wide range of environmental conditions, including temperature (up to 120 °C), pH (2–13), and salinity (0–50 %, w/v). The biosurfactants were found to retain surface-active properties under the extreme conditions. Additionally, the biosurfactants were successful in a test to simulate microbial enhanced oil recovery, removing 90.0 and 93.9 % of crude oil adsorbed on sand and filter paper, respectively. Fourier transform infrared spectroscopy showed that the biosurfactants were a mixture of lipopeptides, which are powerful biosurfactants commonly produced by Bacillus species.ConclusionsThe study highlights the usefulness of optimization of carbon and nitrogen sources and their effects on the biosurfactants production and further emphasizes on the potential of lipopeptide biosurfactants produced by B. atrophaeus 5-2a for crude oil removal. The favorable properties of the lipopeptide biosurfactants make them good candidates for application in the bioremediation of oil-contaminated sites and microbial enhanced oil recovery process.
Highlights
Lipopeptides are known as promising microbial surfactants and have been successfully used in enhancing oil recovery in extreme environmental conditions
Effect of carbon source on biosurfactant production Bacillus atrophaeus 5-2a was able to grow and produce biosurfactants utilizing all of the carbon sources tested, except paraffin (Table 1)
Oil reservoirs are harsh environments, with the potential of high salinity and a wide range of pH values; the observed stability of the biosurfactants assessed in this study, over the pH range of 6–13 and salinity concentrations of 0–15 %, indicates that they would be suitable for oil recovery in most reservoirs. These results show that the biosurfactants from B. atrophaeus 5-2a are good candidates for application in microbial enhanced oil recovery (MEOR)
Summary
Lipopeptides are known as promising microbial surfactants and have been successfully used in enhancing oil recovery in extreme environmental conditions. We evaluated the crude oil removal efficiency of lipopeptide biosurfactants produced by B. atrophaeus 5-2a and their feasibility for use in microbial enhanced oil recovery. Based on the types of biosurfactant-producing microbial species and the nature of their chemical structures, biosurfactants can be roughly divided into four groups: lipopeptides and lipoproteins, glycolipids, phospholipids, and polymeric surfactants [8]. Among these four groups, the best-known compounds are lipopeptides, produced by Bacillus species, and glycolipids, produced by Pseudomonas species [9]. Surfactin is known as a powerful microbial surfactant with high surface activities and has been successfully used in enhancing oil recovery [12,13,14]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
