HPLC spectrograms for surfactin production. a Standard surfactin. b Surfactin from Bs-916.c Surfactin from Bs-H74. d Surfactin from Bs-M49. The system was operated at a flow rate of 1.0 ml/min and monitored at 205 nm with the solvent acetonitrile-3.8 Mm trifluoracetic acid (80:20 [vol/vol])