Fig. 5

Detection of the noreugenin synthesis intermediate 1-(2,4,6-trihydroxyphenyl)butane-1,3-dione (TPBD) in extracted cultivation samples. a Exemplary chromatogramm of an extracted cultivation sample both as total ion current and the individual m/z ratios. b Total ion current chromatogramms of extracted samples resembling the spontaneous cyclization of TPBD towards noreugenin over the cultivation time. For better visualization, the benzoic acid signal was removed from the chromatogramm. c Growth curve and product abundance for the strain C. glutamicum C5 fasO_BCD1 P_O6-iolT1 ∆pyc pMKEx2-pcs_AaCg-short. Unavailability of an authentic TPBD standard prevented quantification of this particular molecule. To evaluate product formation over time, the normalized signal areas of the molecules of interest (Area_moi) TPBD and noreugenin were added up. Signal area of the internal standard (Area_is) benzoic acid was used for normalization. The calculated ratios are depicted on the primary Y-axis. At the given sampling time points, OD₆₀₀ of the cultures was also determined (filled circles, shown on secondary Y-axis). The obtained data represent mean values with standard deviations from biological triplicates