Short-chain FA analysis by GC and GC-MS. Short-chain FAs from
anaerobic cell culture supernatants were detected and quantified
using a Varian 450 gas chromatograph fitted with an Agilent HP-5MS
column and flame-ionization detector. Supernatants were filtered using
a Nalgene 0.2 mm syringe filter and 1 ml was injected into the chromatograph.
The method used a 10 : 1 split ratio and a 30 ml min21
flow rate with helium as the carrier gas. The oven was held at 40 uC for
1 min followed by a ramp of 10 uC min21 up to 240 uC at which point
the temperature was held at 240 uC for 15 min.