Optical density at 660 nm was measured with a Libra S11 spectophotometer (Biochrom, Cambridge, United Kingdom). HPLC analysis of sugar and metabolite concentrations was performed with an Agilent Infinity 1260 chromatography system (Agilent Technologies, Santa Clara, CA, United States) with an Aminex HPX-87 column (Bio-Rad, Lunteren, Netherlands) at 65°C, eluted with 5 mM H2SO4 (Diderich et al., 2018 (link)). Vicinal diketone concentrations (diacetyl and 2,3 pentanedione) were measured using static headspace gas chromatography in a 7890A Agilent GC (Agilent) with an electron capture detector on a CP-Sil 8 CB capillary column, prior to injection 450 μl of supernatant was mixed with 50 μl of 1 mg/L 2,3 hexanedione which acts as an internal standard, and samples were pre-heated for 30 min to 65°C (Brickwedde et al., 2017 (link)). Injection was performed with a CTC Combi Pal headspace autoinjector (CTC analytics AG, Zwingen, Switzerland). Significance of data was assessed by an unpaired two-tailed Student’s t-test with a 95% confidence interval.
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