Rxi 5sil column

FAMEs were analysed by GC-2010 Plus Gas chromatography (Shimadzu, Japan) equipped with AOC-20 i Auto injector and GCMS-QP2010 SE Gas chromatography mass spectrophotometry using a slightly polar RXi-5Sil column (Restek; 30 m × 250 μM id × 0.25 μM film). Injector port and detector were set up at 250 and 230 °C, respectively, and helium (He) was used as carrier gas. Initially, column temperature was maintained at 120 °C for 5 min, followed by increasing to 240 °C in 30 min and held at 240 °C for 25 min. The FAMEs were identified by comparing their fragmentation pattern and retention time (RT) with authentic standards and also with the NIST library (Saini et al. 2014b (link)). Standard mixtures of fatty acid methyl esters (CRM47885–Supelco 37 Component FAME Mix) were purchased from Sigma Aldrich, St. Louis, MO, USA.

Analyses were performed using a Pegasus 4D time-of-flight mass spectrometer (LECO) equipped with a Gerstel MPS2 autosampler and an Agilent 7890A oven. Derivatization products were separated on a (30 m × 0.25 mm i.d. ×0.25 μm) Rxi^®-5Sil column (Restek) with an IntegraGuard^® pre-column using ultrapure He at a constant flow of 1 mL min^–1 as carrier gas. The linear thermal gradient started with 1 min at 50°C, followed by a ramp to 330°C at 20°C min^–1. Final temperature was held for 5 min prior to returning to initial conditions and mass spectra were collected at 17 spectra s^–1. The injection port was held at 250°C, and an aliquot of the sample (1 μL) was injected.

The analysis of terpene products (C₁₀–C₂₅) was performed as described previously (Falara et al., 2011). Briefly, 1 μl of sample was autoinjected into a Shimadzu QP‐2010 SE GC‐MS system equipped with a Rxi‐5Sil column (30 m length, 0.25 mm i.d., and 0.25 μm film thickness; Restek, Bellefonte, PA, USA). Analysis of isoprene was performed by directly injecting the SPME fibre into the Shimadzu QP‐2010 SE GC‐MS system equipped with the Rxi‐5Sil column. The analysis of prenyltransferase assay products was performed using an EC‐WAX column (30 m length, 0.32 mm i.d., and 0.25 μm film thickness; Grace, Columbia, MD, USA). The identification methods for each terpene compound are listed in Table S2. Details of GC–MS parameters can be found in Methods S1.