TABLE 6.
MALDI-TOF mass spectrometric characterization of the surfactin biosurfactants produced by B. subtilis C-1 after separation by reversed-phase HPLC on ODS Hypersil C18a
| Fractions | Mass peak (m/z) | Amplitude (cm) | Assignment (surfactin species) |
|---|---|---|---|
| 24-26 | 994.2 | 4.5 | Val-7 C13, [M+H]+ |
| 1016.7 | 14.8 | Val-7 C13, [M+Na]+ | |
| 1032.7 | 3.6 | Val-7 C13, [M+K]+ | |
| 27-29 | 1030.7 | 14.8 | Leu/Ile-7 C13, [M+Na]+ |
| 1046.7 | 5.0 | Leu/Ile-7 C13, [M+K]+ | |
| 30-32 | 1022.7 | 1.3 | Leu/Ile-7 C14, [M+H]+ |
| 1044.7 | 14.9 | Leu/Ile-7 C14, [M+Na]+ | |
| 1060.7 | 8.0 | Leu/Ile-7 C14, [M+K]+ | |
| 37-39 | 1036.7 | 1.1 | Leu/Ile-7 C15, [M+H]+ |
| 1044.7 | 1.2 | Leu/Ile-7 C14, [M+Na]+ | |
| 1058.7 | 12.4 | Leu/Ile-7 C15, [M+Na]+ |
a
Surfactins were fractionated by using a 20 to 100% acetonitrile linear gradient for 60 min. Eluent A was 20% (vol/vol) acetonitrile in 100 mM ammonium acetate (pH 6.9). Eluent B was 100% acetonitrile. The UV absorbance was monitored at 220 nm. The flow rate was 0.5 ml/min. In the collected fractions surfactin isoforms were identified by MALDI-TOF mass spectrometry. The mass data represent monoisotopic mass numbers.