Fumaric acid producer organisms

L-Malic acid can also be produced from glucose using a combination of a fumaric acid producer Rhizopus arrhizus) and an organism with a high fumarase activity in the same fermentor [89,90]. 

Next to fumarate reduction, some organisms use specific reactions in lipid biosynthesis as an electron sink to maintain redox balance in anaerobically functioning mitochondria. In anaerobic mitochondria two variants are known the production of branched-chain fatty acids and the production of wax esters. The parasitic nematode Ascaris suum reduces fumarate in its anaerobic mitochondria, but instead of only producing acetate and succinate or propionate, like most other parasitic helminths, this organism also use the intermediates acetyl-CoA and propionyl-CoA to form branched-chain fatty acids (Komuniecki et al. 1989). This pathway is similar to reversal of P-oxidation and a complex mixture of the end products acetate, propionate, succinate and branched-chain fatty acids is excreted. In this pathway, the... 

Until now, examples were discussed in which amino acids are produced from mixed organic matter substrates. It is also possible to start with defined chemical compounds. An example is the synthesis of L-alanine from fumaric acid in a two-step reaction. Other examples for a highly selective fermentation are the synthesis of L-Dopa from orthocatechol and of L-tyrosine from phenol. 

Fumaric acid is another organic acid produced by Rhizopus, in particular Rhizopus stolonifer. The presence of fumaric acid has also been found to arise from the addition of synthetic malic acid and is sometimes considered as an index of adulteration when confirmed by analysis of D-malic acid (not present in malic acid from natural sources) (Trifiro et al., 1997). 

Rhizopus oryzae is an indispensable microorganism in industrial fermentation, as it is widely employed to produce L-lactic acid as well as other organic acids. This organism is able to produce only one stereospecific product (L-lactic acid), rather than a racemic mixture and can, therefore, fulfill the need for producing a food additive to be used as both acidulant and preservative. During L-lactic acid fermentation many other metabolites can be produced as by-products. These include fumaric acid, malic acid, ethanol, and the like. However, these metabolites can greatly influence the downstream process and the quality of the L(+)-lactic acid produced. Fumaric acid is the main by-product, as a result of a special metabolic pathway in L-lactic acid production by R. oryzae (Wang et al., 2005). 

Molecules containing carboxylic acid functionalities are not confined to organic systems. For example, the C=C double bond in fumaric acid can interact with a low oxidation state metal centre (see Chapter 23) to form organometallic compounds such as Fe(C0)4(r -H02CCHCHC02H) the T -prefix (see Box 18.1) indicates that the two carbon atoms of the C=C bond of the fumaric acid residue are linked to the Fe centre. Hydrogen bonding can occur between adjacent pairs of molecules as is depicted below, and such interactions extend through the solid state lattice to produce an extensive, three-dimensional array. 

Another acid that develops during fermentation due to the action of yeast is succinic or 1-4-butanedioic acid. Concentrations in wine average 1 g/1. This acid is produced by all living organisms and is involved in the Upid metabolism and the Krebs cycle, in conjunction with fumaric acid. It is a di-acid with a high pK (Table 1.3). Succinic acid has an intensely bitter, salty taste that causes salivation and accentuates a wine s flavor and vinous character (Peynaud and Blouin, 1996). 

MICROBIAL SYNTHESIS OF FUMARIC ACID 15.2.1 Producer Organisms... 

There are several organisms that can accumulate fumaric acid when given the proper conditions. Rhizopus nigricans was the first fungus described to produce fumaric acid by Ehrlich (1911). The main organism used in industry and most extensively described in the literature is R. oryzae earlier termed R. arrhizus. A survey of Mucorales... 

To enable the biological route, the producing organism should be able to accumulate higher final concentrations of fumaric acid, at a lower pH, to simplify the... 

Fumaric acid is a naturally occurring key intermediate in the citrate cycle and therefore present in a very wide range of organisms. Some microorganisms excrete fumaric acid as fermentation product. Fungi, in particular, are known for their organic acid producing capability and have been used in fermentation processes for fumaric acid production. This will be discussed later. 

Rhodes RA, Lagoda AA, Jackson RW, Misenhei TJ, Smith ML, Anderson RF (1962) Production of fumaric acid in 20 liter fermentors. Appl Microbiol 10 9-15 Riscaldati E, Moresi M, Federici F, Petruccioli M (2000) Direct ammonium fumarate production by Rhizopus arrhizus under phosphorous limitation. Biotechnol Lett 22 1043-1047 Roa Engel CA (2010) Integration of fermentation and crystalhsation to produce organic acids. 

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