BATCH KINETICS OF CORYNEBACTERIUM-GLUTAMICUM DURING GROWTH ON VARIOUSCARBON SUBSTRATES - USE OF SUBSTRATE MIXTURES TO LOCALIZE METABOLIC BOTTLENECKS

Growth of Corynebacterium glutamicum on various carbon substrates has been described kinetically under batch culture conditions on fully def ined medium. The use of lactate (major fermentation end-product under O-2 limitation) led to pyruvate overflow during exponential growth, al though pyruvate was reconsumed late in the growth period when both spe cific rates and residual lactate concentration had diminished. During growth on glucose/lactate mixtures the metabolic architecture was such that simultaneous substrate consumption was observed and, in general, specific rates were correlated with mixture composition. Pyruvate ove rflow was, however, emphasised and correlated with the flux arriving a t pyruvate, suggesting that pyruvate dehydrogenase activity may be rat e-limiting under these conditions. The use of lactate/acetate mixtures , in which pyruvate overflow was not observed until all the acetate ha d been consumed, again suggests a metabolic bottleneck at the level of pyruvate dehydrogenase. The lack of detectable pyruvate overflow duri ng growth on glucose, despite rapid rates of substrate consumption, ca n be attributed to carbon distribution through central metabolism and the tight control exerted over glucose uptake via the phosphotransfera se system.