Strains central carbon metabolism

Metabolic flux analysis using isotope labelling methods has been recently applied to the characterisation of several B. megaterium strains [87, 88], The determination of the isotope labelling of the amino acids was carried out with GC-MS. Fluxes of the central carbon metabolism were estimated following the labelling pattern of the amino acids from their precursors. 

Cultivation of RB50 [pRF69] with fractional C-labeled glucose as carbon source and metabolic flux balancing indicated that riboflavin formation in this strain was still limited by the fluxes through the terminal biosynthetic rather than the central carbon metabolic pathways. To debottleneck the riboflavin biosynthetic pathway further, a similar approach as described above was applied to introduce a second P poz-driven and amplifiable rib expression cassette linked to a tetracycline resistance marker at the bpr locus (map position... 

If the chromosomal ilv fragment was derived from the K-12 strain of E, coli, it would have to contain an ilvO mutation so that ilvG would be expressed. See Figure 1.) Such a plasmid would be even more effective if the Inserted DNA carried an ilvA lesion, l.e., was threonine deaminase negative. Overproduction of valine would be expected, since the valine pathway derives its carbon exclusively from a key intermediate in the central metabolic route, pyruvate. Flow into the pathway would then never be restricted as long as ample carbon source was present. 

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