Production of surfactin isoforms by Bacillus subtilis BS-37 and its applicability to enhanced oil recovery under laboratory conditions

• The proportion of surfactin isoforms altered when cultured in different mediums.
• Surfactin products with different proportion of C15-surfactin were tested for oil-washing and oil displacement.
• Surfactin products have a very low CMC of 20 mg/l (20 μM).
• Surfactin products containing more C15 component showed the better oil-washing efficiency and oil displacement efficiency.
• The produced surfactins have a huge potential in microbial enhanced oil recovery.

Natural surfactin is a mixture of cyclic lipopeptides built from variants of a heptapeptide and a β-hydroxy fatty acid with chain lengths of 13–15 carbon atoms. Bacillus subtilis BS-37 was a high-yield mutation strain; the titers of surfactin was 413 mg/l and 585 mg/l with 74.2% and 51.6% proportions of C15-surfactin when BS-37 was cultured in LB medium and glucose medium, respectively. The surfactin products had a low critical micelle concentration (CMC) of 20 mg/l (20 μM), and showed nice stability under strong alkali environment, high concentration of minerals and high temperature. The more C15-surfactin content in products, the better oil-washing efficiency and oil displacement efficiency was. At the concentration of 30 mg/l, surfactin products showed 88.5% of oil-washing efficiency and 13.48% of crude oil displacement efficiency, suggesting its promising application in enhancing oil recovery.

Figure optionsDownload as PowerPoint slide