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

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.