Nature of the Cation Exchanges during Short-Period Yeast Fermentation

Abstract

DURING the fermentation of glucose by yeast, Pulver and Verzar¹ showed that potassium was absorbed from the external fluid and released again towards the end of fermentation. Leibowitz and Kupermintz² showed a similar occurrence in bacteria (B. coli). These workers believed the potassium changes to be specific for this ion, but it was shown by us³ that 'ammonia' yeast in which all the potassium of the cells was replaced by NH₄⁺ behaved in a similar way with respect to the NH₄⁺ ion. An explanation of the process was advanced in which it was considered that potassium entered with phosphate and, this being esterified, held the potassium inside electrostatically, more potassium entering then to equalize the products of potassium and phosphate ion concentrations without and within. Towards the end of fermentation, this process was presumably reversed, and so accounted for the potassium or ammonium released.