Fig. 5: Effects of accumulated metabolic engineering on pleuromutilin production.

a The pathways involved in pleuromutilin production with the enzymes catalysing each reaction and a citrate exporter CEX. The processes with the proteins indicated as blue box were blocked by gene deletion, and those with the proteins indicated as orange box were potentiated by gene overexpression. To activate HMGRs, their truncated variants were also overexpressed. Pleuromutilin production (b) and extracellular/intracellular mevalonate amount (c) in the indicated strains. The strains were cultured in MPY liquid medium at 30°C for 5 days. “Δ” indicates deletion of adh and AocexA, and “O/E” indicates overexpression of the corresponding genes including overexpression of the truncated HMGR genes. Data are shown as means ± standard deviation (S.D.) with a dot plot indicating each data of three independent experiments. Data are analysed using Tukey’s multiple comparison test, and means sharing the same letter are not significantly different (p > 0.05). The significance of intracellular mevalonate is indicated as a’ and b’ (c).