METABOLIC FLUX DISTRIBUTION IN CORYNEBACTERIUM MELASSECOLA ATCC-17965FOR VARIOUS CARBON-SOURCES

The distribution of carbon in the metabolic network of a bacterial cel l was estimated by a mass-balance-based intracellular flux computation method. It was applied to the growth phase of Corynebacterium melasse cola, a glutamic acid producing bacterium, using experimental producti on yields of biomass, lactate and acetate measured during batch cultur es on glucose, fructose, and various mixtures of both sugars. This flu x computation method identifies the direction of the 86 reactions that ensure proper metabolic function during the growth phase of C. melass ecola. Flux ratios allow comparison of calculated and relevant experim ental yields. The results highlight the key influence of the biomass p roduction yield Y-x-O2 on the overall distribution of carbon; the prop ortion of carbon drained in the pentose-P pathway fell from a value in the range of 54% to 47% on media containing glucose (Y-x-O2 = 1.75 to 1.56 g X/g O-2) to 37% on fructose medium (Y-x-O2 = 1.36 g X/g O-2). The highest maintenance requirement was calculated on fructose medium (J(m) = 290 mol ATP/100 mol fructose) which must be connected to a low er efficiency of cell multiplication observed on this substrate. Anoth er important result was that the significant decreases in experimental values of production yields and rates observed on fructose medium whi ch were related to the operation of the FBPase. In particular, it was estimated that, as long as the proportion of glucose in the carbon sou rce remains above 22% (78% fructose), the operation of the FBPase is n ot necessary and the bacteria exhibit behavior similar to that observe d on glucose alone; this result is consistent with experimental observ ations. (C) 1996 John Wiley & Sons, Inc.