Effect of process parameters on succinic acid production in Escherichia coli W3110 and enzymes involved in the reductive tricarboxylic acid cycle

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Abstract:

The effect of process optimization on succinic acid production by Escherichia coli W3110 and on enzymes involved in the reverse tricarboxylic acid cycle was studied. Approximately, 7.02 g L–1 of succinic acid was produced in 60 h at pH 7.0 in 500 mL anaerobic bottles containing 300 mL of the medium, wherein the sucrose concentration was 2.5%, the ratio of tryptone to ammonium hydrogen phosphate was 1:1, and the concentration of magnesium carbon ate was 1.5%. When these optimized fermentation conditions were employed in a 10 L bioreactor, 11.2 g L–1 of succinic acid was produced in 48 h. This is a 10-fold increase in succinic acid production from the initial titer of 0.94 g L–1. This clearly indicates the importance of process optimization, where by manipulating the media composition and production conditions, a remarkable increase in the production of the desired biomolecule can be obtained. The production of succinic acid is a multi-step reaction through the reverse tricarboxylic acid cycle. A linear relationship was observed between succinic acid production and the enzyme activities. The enzyme activities were found to increase in the order phospho-enol-pyruvate carboxylase < malate dehydrogenase < fumarase < fumarate reductase. The activity of phospho-enol-pyruvate carboxykinase was also estimated. Results indicate that this enzyme was not a very active participant in the production of succinic acid, since it catalyzes the phosphorylation of oxaloacetic acid to yield phospho-enol-pyruvate.Key words: anaerobic production, succinic acid, Escherichia coli, process optimization, reverse tricarboxylic acid cycle enzymes, fermentation.

Nous avons étudié les effets de l'optimisation du processus de fermentation sur la production d'acide succinique par Escherichia coli W3110 et sur les enzymes impliquées dans le cycle à rebours des acides tricarboxyliques. Approximativement 7,02 g L–1 d'acide succinique ont été produits en 60 h à pH 7,0 dans des bouteilles anaérobiques de 500 mL contenant 300 mL de milieu auquel ont été ajoutés 2,5 % de sucrose et 1,5 % de carbonate de magnésium alors que la proportion de tryptone et de phosphate d'ammonium était de 1:1. Lorsque ces conditions de fermentation optimisées ont été employées dans un bioréacteur de 10 L, un total de 11,2 g L–1 d'acide succinique a été obtenu en 48 h. Ceci représente une augmentation de 10 fois de la production d'acide succinique, allant d'un titre initial de 0,94. Ceci met clairement en évidence l'importance de l'optimisation où la manipulation de la composition des milieux et des conditions de production permet d'obtenir une augmentation remarquable de la production d'une biomolécule donnée. La production d'acide succinique se déroule en plusieurs étapes à travers le cycle à rebours des acides tricarboxyliques. Une relation linéaire a été observée entre la production d'acide succinique et l'activité des enzymes. Cette activité s'ordonne ainsi : phospho-énol-pyruvate carboxylase < malate déshydrogénase < fumarase < fumarate réductase. L'activité de la phospho-énol-pyruvate carboxykinase a aussi été estimée. Les résultats indiquent que cette enzyme ne participe pas très activement à la production d'acide succinique car elle catalyse la phosphorylation d'acide oxaloacétique en phospho-énol-pyruvate.Mots clés : production anaérobique, acide succinique, Escherichia coli, optimisation du processus, enzymes du cycle à rebours des acides tricarboxyliques, fermentation.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: September 1, 2006

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  • Published since 1954, this monthly journal contains new research in the field of microbiology including applied microbiology and biotechnology; microbial structure and function; fungi and other eucaryotic protists; infection and immunity; microbial ecology; physiology, metabolism and enzymology; and virology, genetics, and molecular biology. It also publishes review articles and notes on an occasional basis, contributed by recognized scientists worldwide.
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