Dynamics of glutamate synthesis and excretion fluxes in batch and continuous cultures of temperature-triggered Corynebacterium glutamicum.

Corynebacterium glutamicum 2262 strain, when triggered for glutamate excretion, experiences a rapid decrease in growth rate and increase in glutamate efflux. In order to gain a better quantitative understanding of the factors controlling the metabolic transition, the fermentation dynamics was investigated for a temperature-sensitive strain cultivated in batch and glucose-limited continuous cultures. For non-excreting cells at 33 degrees C, increasing the growth rate resulted in strong increases in the central metabolic fluxes, but the intracellular glutamate level, the oxoglutarate dehydrogenase complex (ODHC) activity and the flux distribution at the oxoglutarate node remained essentially constant. When subjected to a temperature rise to 39 degrees C, at both high- and low-metabolic activities, the bacteria showed a rapid attenuation in ODHC activity and an increase from 28% to more than 90% of the isocitrate dehydrogenase flux split towards glutamate synthesis. Simultaneously to the reduction in growth rate, the cells activated a high capacity export system capable of expelling the surplus of synthesized glutamate.