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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    The amount of glycerol normally produced in the absence of sulphite is about 2 to 3 per cent, of the sucrose fermented, whilst acetaldehyde is present, if at all, only in traces, so that there can be no doubt of the enormous increase in the quantity of these substances formed as the result of the addition of the sulphite. Precisely similar lesults are produced by the addition of the insoluble sulphites of calcium, magnesium and zinc [Neuberg and Reinfurth, 1919]. The fixation method is most satisfactory with living yeast, but also succeeds with yeast preparations [Neuberg and Reinfurth, 1919]. During the fermentation of sugar by dried yeast in presence of phos- phate, the production of acetaldehyde can also be demonstrated by the addition of sulphite [Hemmi, 1923]. Both glucose and pyruvic acid, like acetaldehyde, form compounds with sodium bisulphite. That of glucose is unstable and is largely hydrolysed in aqueous solution, so that fermentation, either of the complex or of the free glucose, proceeds as usual. The pyruvic acid intermediately produced, probably forms the stable bisulphite com- pound, CH3 • C(0H)S03Na • COOH, which however is readily fer- mented. This has been proved by special experiments [Neuberg and Reinfurth, 1920, 1, 2 ; see also Zerner, 1920] in which it was found that pyruvic acid was fermented even in the presence of excess of sodium sulphite or, better still, of calcium sulphite. Hence it is that the aldehyde is the substance fixed and not the pyruvic acid. In- crease of sulphite beyond a certain limit necessitates dilution of the solution and does not increase the yield of glycerol. A precisely similar influence on the course of the fermenta- tion is observed when the sulphite is replaced by dimethyl-cyclo- hexanedione, (CEI3)2C6H602 (dimedone), a neutral very sparingly soluble substance, which reacts with aldehyde but not with glucose or pyruvic acid [Neuberg and Reinfurth, 1920, 3]. The aldehyde is then found at the close of the fermentation in the form of anhydroacetaldehyde- frzk-dimethyl-cycD-hexanedione (aldomedone) : (CH3)2C6H602 + CH3 • CHO -> [(CH3)2 • C6H502]2 : CH • CH3. This affords additional and conclusive evidence that it is the spec- ific power of combining with the aldehyde and not merely the alkalinity of the reagent which is the decisive factor in the sulphite fixation method. Thiosemicarbazide [Neuberg and Kobel, 1927, 2] and even charcoal [Abderhalden and Glaubach, 1922] can also be used as fixation agents. Experiments carried out in presence of sulphite show that the
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