The effect of redox dyes on the active transport of hydrogen, potassium and sodium ions across the yeast cell membrane

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Abstract
The resting anaerobic potential of suspensions of baker''s yeast was found to lie in the region -20 to -40 mv (Eh value at pH 4.5). Fermentation caused a marked increase in this potential; the steady-state potential during fermentation can be greatly altered by 10-4 [image] redox dyes. Dyes which raise or lower the potential also raise or lower the excretion of H+ or the active absorption of K+. K absorption or H+ excretion are decreased to about 30% or less of control values when the potential is lowered by about 60 mv with the series of dyes studied. At the same time no appreciable effect is observed on the ethanol or CO2 production. Inorganic redox systems (ceric sulfate, chromic chloride, titanous chloride and stannous chloride) have a similar effect, but for a given potential change the effect is smaller with the inorganic redox system than with the redox dyes. A Na-rich yeast gives a higher potential during fermentation than normal yeast, and changes of potential produced by redox dyes, in the absence of K+, have the opposite effect on active Na+ excretion from that which they have on active K+ absorption.