2.4. Analytical method
The mixed acids produced in culture broths were measured
using a high-performance liquid chromatography system (Agilent
1200) equipped with a refractive index detector (RID) and Aminiex
HPX-87H column (300 78 mm; Bio-Rad) after centrifugation at
13,000 rpm for 5 min. The mobile phase was 2.5mMH2SO4 and the
flow rate was 0.5 ml/min during elution. The column and cell
temperature were maintained at 65 C and 45 C, respectively.