Biological production of acid and alkali. 1. Quantitative relations of succinic and carbonic acids to the potassium and hydrogen ion exchange in fermenting yeast

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Abstract
When baker''s yeast ferments 5% (wt./vol.) unbuffered glucose, there being about an equal volume of cells to sugar soln., succinic acid is excreted to about 40-50 m. eq./l. of external fluid. With 0.1-0.2 [image] KC1 in the glucose soln. there is but a small increase in total acid excreted, but the succinic acid is much decreased and free H ions appear in roughly similar amt., usually near 20 m. eq./l. With prolonged oxygenation before fermentation, the succinic acid excretion is greatly lessened and very little total ether-extractable acids are found in the yeast suspension. At the same time, the max. formation of free acid appears when KCl is incorporated. A pH as low as 1.4 was twice noted, and 1.6 frequently observed. With bubbling with CO2 and with KCl, acid-labile CO2 increases up to about an 80% equivalence. This acid-labile CO2 was shown to be HCO3. As the succinic acid excreted in the presence of KCl is decreased, as by prior oxygenation, the acid-labile CO2 is increased in the cells relative to the control without KCl. Succinic and carbonic acids were the only acids of quantitative significance for association, as anions, with the K ions absorbed, apart from possible changes in the fixed buffering of the cells. Succinic acid excreted outside the cells during fermentation remains for many hours unchanged in concn., but the free H ions formed by the exchange for K practically disappear in 3-4 hr.