Ethanol, fermentation pyruvic acid intermediate

In this case, although the hypothetical balanced process yields a net 4 moles of methanol and 2 moles of CO2 per mole of glucose converted, twice the reducing power is needed compared to the ethanol case and cleavage of two additional carbon-carbon bonds is also required. Decarboxylation of pyruvic acid has not been reported to proceed in this manner. These observations, however, do not preclude the possibility of other biochemical pathways and intermediates to fermentation methanol. 

Most bacteria convert malic acid to lactic acid with an intermediate formation of pyruvic acid, while Oenococcus oeni (previously classified as Leuconostoc oenos) expresses the malolactic enzyme to directly convert malic acid in one-step reaction. O. oeni has been extensively studied for controlled MLF of wine due to its higher tolerance to ethanol, low pH, and Yeasts like Schizosaccharomyces pombe and Saccharomyces strains can also convert malic acid through a maloethanolic-type fermentation. Lactic acid is less acidic than malic acid, and as a conseqnence, MLF leads to improvement of the sensory properties and biological stability of the wines. Additionally, the production of various other by-products of the MLF reaction may affect wine flavor positively. 

Citric acid is a major end product of the oxidative metabolism of carbohydrate, ethanol, and acetic acid in many molds, e.g., Aspergillus niger. Evidence of the mechanism of citric acid formation is incomplete but the existing data are compatible with the assumption that citric acid arises, as an animal tissue, by condensation of oxalacetate with active acetic acid, as first proposed by Raistrick and Clark. Experiments with isotopic CO2 on Aspergillus suggest that the oxalacetate required for the synthesis of citrate can be formed by the carboxylation of pyruvate formed as an intermediate in the anaerobic fermentation.It is very... 

Cocoa bean fermentation is a mixed-culture process, consisting initially of fermentations by yeast and lactic acid bacteria followed by oxidation of the fermentation products ethanol and lactic acid into acetic acid and acetoin by several Acetohacter strains, of which /I. pasteurianus is the prominent one (Moens et al. 2014). A C-based carbon flux analysis of Acetohacter during cocoa pulp fermentation-simulating conditions revealed a functionally separated metabolism during co-consumption of ethanol and lactate. Acetate was almost exclusively derived from ethanol, whereas lactate served for formation of acetoin and biomass building blocks. This switch was attributed to the lack of phosphoenolpyruvate carboxykinase and malic enzyme activities, which prevents conversion of oxalo-acetate and malate formed by acetate metabolism in the TCA cycle to PEP and pyruvate and subsequently to acetoin (Adler et al. 2014). Lactate, on the other hand, can be converted to pyruvate, which is then used for acetoin formation or, after conversion to PEP by pymvate phosphate dikinase, for gluconeogenesis. The inability of conversion of TCA cycle intermediates to PEP resembles the situation in G. oxydans, where in addition no enzyme for conversion of pyruvate to PEP is present. 

Under anoxic condition of succinic acid production, phoshpoenolp3nuvate (PEP), one of the central intermediates during mixed acid fermentation, is converted by two enzymes in A. succinogenes 130Z named PEP carboxykinase (PPCK) and pyruvate kinase [16,23]. PPCK is a C02-fixing enzyme that converts PEP to oxaloacetate toward the flux to the formation of succinic acid [20, 23]. Pymvate kinase converts PEP to pyruvate, which is consequently converted to end fermentation by-products such as acetic acid, formic acid, and ethanol [16]. 

Production of 2,3-BD is via a mixed acid fermentation pathway that also leads to a mix of acetate, lactate, formate, succinate, and ethanol. Juni and Heym (1956) proposed that 2,3-BD is produced in bacteria from pyruvate through the intermediates a-acetolactate and acetoin. Also, microorganisms can degrade 2,3-BD (i.e., it is biodegradable), a feature that may add to its attractiveness as an industrial chemical. 

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