Alcoholic fermentation / by Arthur Harden.

  • Arthur Harden
Date:
1932
Catalogue details

Licence: In copyright

Credit: Alcoholic fermentation / by Arthur Harden. Source: Wellcome Collection.

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    which is to link together two carbon atoms forming a carbon chain. This effect was first observed by Neuberg and Hirsch [1921] who found that when benzaldehyde was added to a fermenting mixture of yeast with sugar or pyruvic acid, phenylacetylcarbinol, C6H5 • CH(OH) • CO • CH3 (in an optically active form [Neuberg and Ohle, 1922, I, 2]) was produced. The reaction occurs with a number of aldehydes [see Neuberg and Liebermann, 1921]. A particularly interesting case is that of acetaldehyde, which is converted into optically active acetoin or acetylmethylcarbinol, CH3 • CO • CH(OH) • CH3. This occurs in the fermentation of pyruvic acid (p. 94) [Hirsch, 1922, 1], as well as when acetaldehyde is added to a fermenting mixture of yeast or an active yeast preparation and sugar [Neuberg and Reinfurth, 1923; Neuberg and Rosenthal, 1924], but not when acetaldehyde is acted on by a glycogen-free yeast in absence of sugar [Neuberg and Simon, 1925]. In the presence of a hydrogen acceptor, such as methylene blue or sulphur, some of the acetaldehyde produced as an intermediate compound in the formation of alcohol (p. 123) escapes reduction and is converted into acetoin, part of which is then reduced to 2*3-buty- lene glycol [Kluvyer, Donker, and Hooft, 1925]. The formation of these products is also favoured by aeration, the oxygen acting as hydrogen acceptor, and they are present in the fermented mash which has been used for the manufacture of pressed yeast (Lufthefe). Acetoin and 2‘3-butylene glycol are formed by many bacteria, and it has been shown that they are produced when the organism is supplied with acetaldehyde [see Harden and Walpole, 1906 ; Harden and Norris, 1912]. The proof of the existence of carboligase in micro- organisms is of great importance, as it points the way to an under- standing of the numerous and essential synthetical reactions which the cell carries out. The reverse change, the enzymic decomposition of acetoin into aldehyde, has not yet been observed. * 7
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