PSMs were analyzed by RP-HPLC/ESI-MS using an Agilent 1260 Infinity chromatography system coupled to a 6120 Quadrupole LC/MS in principle as described62 (link), but with a shorter column and a method that was adjusted accordingly. A 2.1 × 5 mm Perkin-Elmer SPP C8 (2.7 μm) guard column was used at a flow rate of 0.5 ml/min. After sample injection, the column was washed for 0.5 min with 90% buffer A /10% buffer B, then for 3 min with 25% buffer B. Then, an elution gradient was applied from 25% to 100% buffer B in 2.5 min, after which the column was subjected to 2.5 min of 100% buffer B to finalize elution.
Bacillus culture filtrates or (partially) purified lipopeptide (fengycins, surfactins) containing fractions were analyzed using the same column, system, and elution conditions. To quantify production of different fengycins, the two most abundant peaks, corresponding to double and triple charged ions, were used for the integration. Agilent Mass Hunter Quantitative Analysis Version B.07.00 was used for quantification.
Bacillus culture filtrates or (partially) purified lipopeptide (fengycins, surfactins) containing fractions were analyzed using the same column, system, and elution conditions. To quantify production of different fengycins, the two most abundant peaks, corresponding to double and triple charged ions, were used for the integration. Agilent Mass Hunter Quantitative Analysis Version B.07.00 was used for quantification.