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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    aldehyde either by Rimini’s reaction (a blue coloration with diethyl- amine or piperidine and sodium nitroprusside) or by means of p- nitrophenylhydrazine, which precipitates the hydrazone, melting at 128-5° [Neuberg and Karczag, 1911, 2, 3]. Pyruvic acid should yield equal weights of carbon dioxide and acetaldehyde, and the acetaldehyde can be almost completely accounted for when allowance is made for the fact that part of it is converted into acetoin (p. 99). Thus, as the result of an experiment with yeast, 2*86 g. of acetaldehyde and 2*07 g. of acetoin were obtained, equivalent to a total of 4*93 g. of acetaldehyde, whilst the carbon dioxide evolved was 4*82 g. [Neuberg and May, 1923]. The salts of the acids are also attacked, the carbonate of the metal, which may be strongly alkaline, being formed. Thus, taking the case of pyruvic acid, the salts are decomposed according to the following equation :— 2CH3 • CO • COOK + H20 = 2CH3 • CHO + K2C03 + C02. Under these conditions a considerable portion of the aldehyde undergoes condensation to aldol [Neuberg, 1912] :— 2CH3 • CHO = CH3 • CH(OH) • CH2 • CHO. This change appears to be due entirely to the alkali and not to an enzyme since the aldol obtained yields inactive /3-hydroxybutyric acid on oxidation [Neuberg and Karczag, 1911, 3; Neuberg, 1912]. The various preparations derived from yeast which are capable of producing alcoholic fermentation also effect the decomposition of pyruvic acid in the same manner as living yeast [see also Neuberg and Czapski, 1914L this is also true of the precipitate obtained from maceration extract with acetone or alcohol and ether [Neuberg and Rosenthal, 1914 5 Neuberg, 1915? l]» They are, however, more sensitive to the acidity of the pyruvic acid, and it is therefore advisable to employ a salt of the acid in presence of excess of a weak acid, such as boric or arsenious acid, which decomposes the carbonate formed but has no inhibiting action on the enzyme [Harden, 1913 ; Neuberg and Rosenthal, 1913]- Other buffers, e.g. phosphates or acetates, may be employed, and these, moreover, often have a very beneficial effect on the action of living yeasts [Neuberg 1915, I ; Haehn and Glaubitz, 1927, 2], which are moderately sensitive to pyruvic acid; thus digestion for twenty-four hours with a 2 per cent, solution of the acid completely removes their power of decomposing pyruvates. As already mentioned the action is exerted on a-ketonic acids as a class and proceeds with great readiness with oxaloacetic acid,
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