Biological Chemistry - Berezov T. T., Korovkin B. F. 1998

Carbohydrate Metabolism
Glycolysis
Alcoholic Fermentation

Alcoholic Fermentation is carried out by so-called Yeast-like organisms, as well as certain Molds. The overall reaction of alcoholic fermentation can be represented as follows:

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The Mechanism of alcoholic fermentation is remarkably similar to that of Glycolysis. The pathways diverge only after The formation of Pyruvate. In glycolysis, pyruvate is reduced to lactate via the enzyme LDH and the coenzyme NADH. In alcoholic fermentation, this final stage is replaced by two other enzymatic reactions: the pyruvate decarboxylase and Alcohol dehydrogenase reactions.

In yeast Cells (during alcoholic fermentation), pyruvate first undergoes decarboxylation to yield acetaldehyde. This reaction is catalyzed by the enzyme pyruvate decarboxylase, which requires Mg ions and a coenzyme (TPP):

The resulting acetaldehyde accepts hydrogen abstracted from NADH, thereby being reduced to ethanol. This reaction is catalyzed by the enzyme alcohol dehydrogenase:

Thus, the End products of alcoholic fermentation are ethanol and CO₂, rather than lactic acid as seen in glycolysis.

Lactic acid fermentation shares a close resemblance to alcoholic fermentation. The only difference is that in lactic acid fermentation, pyruvic acid does not undergo decarboxylation; instead, much like in glycolysis in animal Tissues, it is reduced via LDH utilizing hydrogen from NADH.

There are two known groups of lactic acid Bacteria. Bacteria of the first group produce exclusively lactic acid during carbohydrate fermentation, whereas bacteria of the second group "yield" one molecule of lactic acid, one molecule of ethanol, and one molecule of CO₂ per glucose molecule.

Other Types of fermentation also exist, yielding end products such as propionic, butyric, and succinic acids, among various Other Compounds.