Alcoholic fermentation / by Arthur Harden.

  • Arthur Harden
Date:
1932
Catalogue details

Licence: In copyright

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

    187/258 page 177
    177 (a) iso Amyl Alcohol. (1) (CH3)2 • CH • CH2 • CH(NH2) • COOH (3) (CH3)2 • CH • CH2 • CHO + C02 Leucine isovaleraldehyde (2) (CH3)2 • CH • CH2 • CO • COOH (4) (CH3)2 • CH • CH2 • CH2OH a-Keto-wovalerianic acid isoamyl alcohol (b) Succinic Acid. (1) COOH • CH2 • CH, • CH(NH2) • COOH (3) COOH • CH2 • CH2 • CHO + C02 Glutamic acid Succinic semialdehyde (2) COOH • CH2 • CH2 • CO • COOH (4) COOH • CH2 • CH2 • COOH a-Ketoglutaric acid Succinic acid In the special case of succinic acid, evidence strongly confirmatory of this view has been obtained by Neuberg and Ringer [191 y 1, 2 ; 1918, 2] who have found that both a-ketoglutaric acid and /3-aldehydo- propionic acid (succinic semialdehyde) are converted by yeast into succinic acid. This transformation is also quantitatively effected by maceration extract (best in the presence of sugar), which, as is well known, does not bring about the characteristic alcoholic fermentation of the amino-acids. It appears therefore that the primary conversion of the amino-acids into ketonic-acids, a change probably accompanied by assimilation of the nitrogen, can only be effected by living, actively fermenting yeast, whereas the subsequent changes occur under the influence of the enzymes which are present in maceration extract, etc. The oxidation of the aldehyde to succinic acid takes place in absence of free oxygen and the source of this oxygen is not yet known. It is interesting to note that bacteria are also capable of producing succinic acid from a-ketoglutaric acid, but it must be remembered that in all probability succinic acid can also be directly produced by many bacteria, e.g. B. coli communis) from sugar, as the amount formed (20 per cent, or even more of the sugar) is greatly in excess of that obtainable from the available glutamic acid. The effect of Ehrlich’s work has been clearly to distinguish the chemical changes involved in the production of fusel oil and succinic acid from those concerned in the decomposition of sugar into alcohol and carbon dioxide, and to bring to light a most important series of reactions by means of which the yeast-cell is able to supply itself with nitrogen, one of the indispensable conditions of life. Glycerol. Of the three chief by-products of alcoholic fermentation, only glycerol remains at present referable directly to the sugar. This sub- 12
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