Skip to main content
Fig. 9 | Microbial Cell Factories

Fig. 9

From: Metabolic flux analysis in Ashbya gossypii using 13C-labeled yeast extract: industrial riboflavin production under complex nutrient conditions

Fig. 9

Intracellular carbon fluxes of riboflavin production with A. gossypii B2 on rapeseed oil and complex medium, which were determined by four parallel 13C-labeled tracer studies using [13C2] glycine, [13C] formate, [13C5] glutamate, and [U13C] yeast extract. The carbon fluxes were normalized to the specific riboflavin production rate (8.7 ± 2.3 µmol g−1 h−1), which was set to 100%. Riboflavin was obtained at the end of the growth phase of riboflavin producing A. gossypii after 144 h. Data are derived from positional 13C enrichment obtained from 13C NMR measurements (Table 3), corrected for natural labeling and dilution effects through unlabeled pre-culture medium. Note that the model is simplified and cannot distinguish between carbon flux through e.g. gluconeogenesis or lower PP pathway as well as pyruvate dehydrogenase. Reaction between OAA/MAL and PEP/PYR pool is a lumped flux. Only reactions necessary for riboflavin biosynthesis were considered and all reactions represent net fluxes. Note that some reactions as shown in Fig. 7 can be expressed as a single reaction, i.e. all decarboxylation reactions and in general all reactions with more than one educt or product can be expressed as a single flux. All fluxes from the medium into the cell are not fluxes based on concentrations, but solely derived from 13C labeling of riboflavin. Note that the conversion of citrate to isocitrate via aconitase most likely does not occur in the peroxisome [68]. 3PG, 3-phosphoplycerate; AcCoAP/M, peroxisomal/mitochondrial acetyl-CoA; AKG, α-ketoglutarate; ArP, 5-amino-6-ribitylamino-2,4(1H,3H)-pyrimidinedione; DRL, 6,7-dimethyl-8-ribityllumazine; CH2-THF, 5,10-methylenetetrahydrofolate; CHO-THF, 10-formyltetrahydrofolate; FA, fatty acids (here: three C17.3 FA); FOR, formate; GAR, glycineamide ribonucleotide; GLU, glutamate; GLY, glycine; GLYINTR, intracellular glycine pool; GTP, guanosine triphosphate; PRA, 5-phosphoribosylamine; PYR, pyruvate; R5P, ribose 5-phosphate; Ru5P, ribulose 5-phosphate; RFV, riboflavin stored in the vacuole; SER, serine; THF, tetrahydrofolate; YE, yeast extract

Back to article page