Ion Transport and Phosphorylation in Dried and Rehydrated Yeast Cells

Abstract

BAKER'S yeast, consisting of almost 70 per cent water, can be dried to a moisture content of 7–8 per cent of dry weight without serious impairment of viability or fermenting capacity^1,2. The cell membrane in such cells seems to be altered in such a way that considerable leakage of cytoplasmic material occurs when the cells are suspended in water at or below room temperature. Suspension of the cells in water at 35°–45° C prevents excessive loss of cytoplasmic constituents³. The “active dry yeast” to be considered here is dried yeast rehydrated at 35° C in which the cellular permeability barrier has been restored. The lipid composition of yeast cells can be altered by this process⁴. I have investigated the question of whether such cells are still capable of active ion transport, which is one of the normal membrane functions^5–7.