(485ab) Effect of Fumarase and Formate Reductase Gene Deletions On Escherichia Coli Fermentation Product Profiles

C4 compounds such as succinate, malate and fumarate are of high industrial importance. They are used as additives in food, pharmaceuticals and as precursors of resins and polymers. They are currently produced from petroleum which could lead to pollution and high price variability. Escherichia coli, a facultative anaerobe microorganism, is able to produce C4 compounds such as malate, fumarate and succinate during its growth, as part of the tricarboxylic acid (TCA cycle) or the anaerobic fermentation using renewable carbon sources. E. coli does not naturally accumulate these compounds in significant quantities or with high yields. Two important reactions in E. coli anaerobic fermentation are the conversion of malate to fumarate and fumarate to the final product succinate. The first reaction is reversible and catalyzed by fumarases. There are three fumarases (A, B and C) in E. coli which are involved in the tricarboxylic acid (TCA) cycle and anaerobic fermentation. It has been reported that the fumarases activities are dependent on the level of oxygen present, cells growth rate and carbon source used (Park and Gunsalus 1995; Tseng et al. 2001). The second reaction is catalyzed by the enzyme fumarate reductase, which is thought to be active only in anaerobic conditions. Therefore, we have investigated the effect of single, double and triple fumarase mutants as well as the effect of fumarate reductase gene deletion on the anaerobic product profile in E. coli with the purpose of increasing the understanding of the importance of these genes in the balance of metabolic fluxes leading to the different anaerobic products.

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Tseng CP, Yu CC, Lin HH, Chang CY, Kuo JT. 2001. Oxygen- and growth rate-dependent regulation of Escherichia coli fumarase (FumA, FumB, and FumC) activity. J Bacteriol 183(2):461-7.