The nature of the cation exchanges during yeast fermentation, with formation of 0·02n-H ion

Publisher Website
Google Scholar
Abstract
The absorption of K+ and its release by yeast in short period fermentation are simulated by the absorption and release of NH4 into ammonia yeast. 10 mg. K/100 ml. is the conc. above which K is absorbed and below which K is released. The H-ion conc. of an unbuffered suspending soln. follows closely the changes of K in fermentation, and when K conc. is raised to N/10 to N/2 the acidity produced can reach pH 1.78 or less. The free H ion equals 80% of K-ion absorbed and the remainder of K-ion enters with Cl. The effect of inhibitors shows that the main source of the acidity lies at or below the level of phos-phopyruvic acid in the breakdown of carbohydrate. During fermentation, yeast cell membranes become more permeable to K, are permeable to Cl, and almost impermeable to Na. Keto acid formation cannot account for acidity.