Rxi 5sil column

For n-butanol quantification, the fermentation broth was centrifuged at 8000 g for 10 min, and the supernatant was collected. Then the n-butanol concentration was determined by gas chromatography-mass spectroscopy (GC-MS) an Agilent 7890 A GC system and HP-INNOWAX column. For the extraction of medium-chain fatty acids (MCFAs), the fermentation broth was centrifuged at 8000 g for 10 min, and the supernatant was collected. Then, the mixture of hexane: chloroform (4:1, vol/vol) was used for extracting the MCFAs. After that, the organic layer was collected and evaporated through nitrogen. To measure the concentration of MCFAs, samples were resolved in a mixture of methanol: sulfuric acid: chloroform (30:3:1, vol/vol/vol) to heat at 70 °C for 1 h. Subsequently, the Fatty acid methyl esters (FAMEs) were extracted by hexane. Finally, the FA methyl esters were measured GC-MS on an Agilent 7890 A GC system and a Rxi-5Sil column (0.25 mm internal diameter 0.10 μm film thickness, 30 m length), following the method of an initial temperature of 35 °C held for 1 min, 6 °C/min to 200 °C, 30 °C/min to 270 °C, held for 1 min.

NMR spectroscopy was performed using Bruker
AV3–400 (liquid nitrogen cryoprobe), Bruker AV3–400
Nano (BBFO-z-ATMA probe), or Bruker AVII-600 (BBO-z-ATMA) instruments.
All kinetic experiments were performed using the latter instrument. ¹H NMR spectra are referenced to residual solvent signals, ¹³C{¹H} NMR spectra are referenced to the deuterated
solvent signal, and ³¹P{¹H} NMR spectra are
externally referenced.^{44 (link)} Chemical shifts
are given in ppm and coupling constants in Hertz. Gas chromatography–mass
spectrometry (GC–MS) analyses were carried out using an Agilent
7890A gas chromatograph fitted with a RESTEK-RXi-5Sil column (30 m
× 0.32 mm I.D. × 0.25 μm) connected to an Agilent
5975C MSD running in an EI mode. GC-FID analyses were carried out
using an Agilent 7890A gas chromatograph fitted with an Agilent HP5
column (30 m × 0.25 mm I.D. × 0.25 μm).