What is fermentation?

1 Answer
Sep 27, 2015

Fermentation is an anaerobic metabolic process in which an organism converts a carbohydrate to an alcohol or an acid.


The first step in all fermentation processes is glycolysis, the conversion of glucose to pyruvate:

#"C"_6"H"_12"O"_6 → "2CH"_3"COCOO"^(−) + "2H"_2"O" + 2"H"^+#

There are two main types of fermentation; one converts pyruvate into lactate (lactic acid) and the other into ethanol.

(from sun.menloschool.org)

In lactic acid fermentation, pyruvate is converted into lactic acid.

#underbrace("CH"_3"COCOO"^-)_color(red)("pyruvate") stackrelcolor (blue)("enzymes")(→) underbrace("2CH"_3"CH(OH)COOH")_color(red)("lactic acid") #

In alcohol fermentation,the pyruvate is decarboxylated to acetaldehyde, and then into ethanol.

#"CH"_3"COCOO"^(-)+ "H"^+ stackrelcolor (blue)("pyruvate decarboxylase")(→) "CH"_3"CHO" + "CO"_2#

#"CH"_3"CHO" stackrelcolor (blue)("alcohol dehydrogenase")(⇌) "CH"_3"CH"_2"OH"#

In an aerobic process, the pyruvate is converted by respiration to carbon dioxide and water.

Here is a summary of the three possible fates of pyruvate:

Pyruvate fates
(rom vishbiochemblog.wordpress.com)