Tartaric metabolism

The results obtained appeared quite promising, but the real sensation was the detection of pyruvate, the salt of 2-oxopropanoic acid (pyruvic acid), which is one of the most important substances in contemporary metabolism. Pyruvic acid was first obtained in 1835 by Berzelius from dry distillation of tartaric acid. The labile pyruvate was detected in a reaction mixture containing pure FeS, 1-nonanethiol and formic acid, using simulated hydrothermal conditions (523 K, 200 MPa). The pyruvate yield, 0.7%, was certainly not overwhelming, but still remarkable under the extreme conditions used, and its formation supports Wachtershauser s theory. Cody concludes from these results that life first evolved in a metabolic system prior to the development of replication processes. 

The main product of anaerobic degradation of sugars by these organisms is lactic acid. Other products of bacterial carbohydrate metabolism include extracellular dextrans (see p. 40)—insoluble polymers of glucose that help bacteria to protect themselves from their environment. Bacteria and dextrans are components of dental plaque, which forms on inadequately cleaned teeth. When Ca salts and other minerals are deposited in plaque as well, tartar is formed. 

Lactic acid bacteria isolated from wine may use residual sugars or alcohol, or decompose organic acids as a source of carbon for growth and energy. Malic, citric, and tartaric acids may be metabolized, depending on conditions. 

Regarding organic acids metabolism, Amati et al. (1983) reported that malic acid is consumed in both natural and conditioned systems, although it was more intense in the latter. This malic acid decrease is probably due to the respiration processes and /or to malic acid conversion into sugar (gluconeogenesis). In contrast, tartaric acid decreases slightly, and no differences were seen between the two drying systems. 

After sterilization, yeast is added to initiate fermentation. McConnell and Schramm (1995) recommend inoculation with no less than 10% by volume. Moreover, as the pH of honey is naturally low and because it is poorly buffered, the pH of must may drop during fermentation to a point limiting yeast efficiency. pH reduction can result from the synthesis of acetic and succinic acids by the yeast cells (Sroka and Tuszynski, 2007). While a rapid decline in pH inhibits undesirable microbial activity (Sroka and Tuszynski, 2007), it also reduces the dissociation of fatty acids in the wort, potentially slowing yeast metabolic action. For this, addition of a buffer is important to maintain the pH within a range of 3.7-4.0 throughout fermentation (McConnell and Schramm, 1995). Calcium carbonate, potassium carbonate, potassium bicarbonate, and tartaric acid are potential candidates. However, as some of these salts can add a bitter-salty... 

Of all the metabolic activities that lactic acid bacteria can carry out in wine, the most important, or desirable, in winemaking is the breakdown of malic acid, but only when it is intended for this to be removed completely from the wine by malolactic fermentation. Although the breakdown of malic and citric acids has considerable consequences from a winemaking perspective, it is also evident that lactic acid bacteria metabolise other wine substrates to ensure their multiplication, including sugars, tartaric acid, glycerine and also some amino acids. We will now describe some of the metabolic transformations that have received most attention in the literature, or which have important repercussions in winemaking. 

Tartaric acid is relatively stable to bacterial activity and can only be metabolized by some Lactobacillus species with the production of acetic acid, lactic acid and succinic acid (Handler 1983). When tartaric acid is metabolised, the volatile acidity increases and the wine acquires an acetic aroma and a disagreeable taste this degradation can be total or partial depending on the bacteria population, but it always decreases wine quality. The tartaric acid degrading capacity is restricted to only a few species Radler And Yannissis (1972) found it in four strains of L. plantarum and one strain of L. brevis. 

Various aldehydes are encountered in wine. The most abundant is acetaldehyde which is both a product of yeast metabolism and an oxidation product of ethanol. Glyoxylic acid, resulting from oxidation of tartaric acid, especially catalyzed by metal ions (Fe, Cu) or ascorbic acid, can also be present. Other aldehydes reported to participate in these reactions include furfural and 5-hydroxymethylfurfural that are degradation products of sugar and can be extracted from barrels (Es-Safi et al. 2000), vanillin which also results from oak toasting, isovaleraldehyde, benzaldehyde, pro-pionaldehyde, isobutyraldehyde, formaldehyde and 2-methylbutyraldehyde which are present in the spirits used to produce fortified wines (Pissara et al. 2003). 

Side-chain oxidized derivatives of ascorbic acid are also implicated in the catabolism of ascorbic acid in plants. Loewus et al. (62) have established the intermediacy of ascorbic acid in the biosynthesis of tartaric acid in the grape. Labeling studies have established a metabolic pathway that must involve C5 and C6 oxidation of ascorbic acid. 

Williams and Loewus (7) prepared l-[4- C]ascorbic acid by the method of Bakke and Theander (8) and showed that this form of specifically labeled ascorbic acid, like L-[l- C]ascorbic acid, was an effective precursor of tartaric acid in grape berries and grape leaves (Table I) (9). Over 98% of the was located in the carboxyl groups of labeled tartaric acid from l-[1- C]- or L-[4- C]ascorbic acid labeled leaves or berries. Only L-(-f)-tartaric acid was formed (10). The C2 fragment of this cleavage, as judged by studies with l-[6- C] ascorbic acid, was recycled into products of hexose phosphate metabolism (5,6,11,12). 

Table I. Conversion of L-Ascorbic Acid the Grape (Metabolic Period, [U C] to Tartaric, 25 h) Acid in [6- C]...

Virginia Creeper leaves were fed L-ascorbic acid with C in Cl, C4, C5, or C6 or on C6 (14). In each experiment, three compound leaves from the fifth position behind the tip of the vine were used. After a 24-h metabolic period, the distribution of radioisotope was determined (Table III). As in the grape, l-[1- C]- and l-[4- C]ascorbic acid produced carboxyl labeled tartaric acid. Virutally no radioisotope appeared in tartaric acid from the other l-[5- C]-, l-[6- C]-, or l-[6- H]ascorbic acid. The larger amount of C02 released by L-[l- C]ascorbic acid labeled leaves has been confirmed in subsequent studies. 

In geranium, the C2-C3 cleavage of L-ascorbic acid is enantiomeri-cally specific (ii). When L-[6- C]ascorbic acid was replaced by d-[6- C] ascorbic acid, labeled tartaric acid was not found in the acid extractable fraction (Table V). There was considerable decomposition of D-ascorbic acid. Only 17% of the D-ascorbic acid remained in the tissues at the end of the metabolic period. Some metabolism of these... 

The most outstanding characteristic of tamarind is its sweet acidic taste, the acid due to mostly tartaric acid. The latter is synthesised in tamarind leaves in the light and translocated to the flowers and fruits (Lewis et aL, 1961 and Patnaik, 1974, both cited in (3)). Tartaric is an unusual plant acid formed from the primary carbohydrate products of photosynthesis, and once formed, it is not metabolically used by the plant (3). The content of tartaric acid does not... 

The first observation of biological enantioselectivity was made by Pasteur himself. He found, in 1858, that when solutions of racemic ammonium tartrate were fortified with organic matter (i.e., a source of microorganisms) and allowed to stand, the solution fermented and (-I-)-tartaric acid was consumed rapidly while (-)-tartaric acid was left behind unreacted. Eventually the (-)-enantiomer was also metabolized, but considerably more slowly than (-t)-tartrate [50]. In later experiments Pasteur showed that the common mold Penicillium glaucum metabolized (-I-)-tartaric acid with high enantioselectivity [51]. He correctly theorized that the enantioselective destruction of tartaric acid by microorganisms involves selective interaction of the tartrate enantiomers with a key chiral molecule within the microorganism [50, 51]. 

It might be of dietary origin, as it is present in many vegetables. It appears, however, that, contrary to previous results, the different isomers of tartaric acid are largely metabolized in the human body when given in small quantities (B4) the products of the enzymatic oxidation of tartaric acid have been studied by Kun and Garcia Hernandez (G4, K21). 

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