Fig. 1

Overall strategy used in this study. a To produce tyrosine from acetate, the SCK1 strain, with amplification of the pathway from PEP to tyrosine, was used [17]. To further amplify the linear pathway from acetate to PEP, acs (encoding acetyl-CoA synthetase) and pck (encoding phosphoenolpyruvate synthase) were overexpressed. Thereafter, the glyoxylate cycle pathway was precisely controlled by varying the expression of aceA (encoding isocitrate lyase). b A schematic showing the pathway optimization strategy. Acetyl-CoA produced from acetate can be metabolized via two different pathways: oxidation into CO₂ and generation of ATP and NADH via TCA cycle, or assimilation as metabolites and cell biomass via the glyoxylate cycle. Replenishment of precursors (PEP from OAA) and energy consumption for tyrosine production should be considered for efficient tyrosine production. This can be implemented by precise control of the glyoxylate cycle. OAA oxaloacetate, CIT citrate, ICT isocitrate, α-KG α-ketoglutarate, SUC succinate, MAL malate, GLY glyoxylate, PEP phosphoenolpyruvate, G-6-P glucose-6-phosphate, E-4-P erythrose-4-phosphate, DHAP dihydroxyacetone phosphate, TYR tyrosine