Fig. 3

Intracellular flux distribution for EG metabolism under a aerobic and b micro-aerobic (oxygen-limiting) conditions. Fluxes predicted by flux balance analysis (FBA) are shown under each reaction arrow. Values in the brackets (units: mmol/gDW hr) represent the lower and upper values obtained from the flux variability analysis (FVA). The FVA flux ranges provide an estimation of the error in the reaction fluxes predicted by FBA, for the selected simulation constraints. Enzymes catalyzing each step are indicated under each reaction arrow. Enzyme acronyms are as follows: PDO (1,2-propanediol oxidoreductase), GCALDD (glycolaldehyde dehydrogenase), GLYCTO2 (glycolate oxidase, ubiquinone-dependent), GLXCL (glycolate carboligase), TRSARr (tartronate semialdehyde reductase), GLYCK2 (glycerate kinase), PGM (phosphoglycerate mutase), ENO (enolase), PYK (pyruvate kinase), MALS (malate synthase), ME1/ME2 (malic enzyme, NAD⁺/NADP⁺-dependent), PDH (pyruvate dehydrogenase), PFL (pyruvate formate lyase), and CS (citrate synthase). Compound acronyms are as follows: EG (ethylene glycol), TSA (tartronate semialdehyde), 2PG (2-phosphoglycerate), PEP (phosphoenolpyruvate), AcCoA (acetyl-CoA). Colours denote the following: exogenous steps (purple), the desired product and its export (red), and metabolic valves (blue). Increased line thickness for the glyoxylate to TSA reaction indicates the 2:1 reaction stoichiometry, accounting for the reduction in total flux observed at the glyoxylate node