INTRACELLULAR PH OF YEAST DURING BREWERY FERMENTATION

The intracellular pH value of Saccharomyces cerevisiae NCYC 1681 was m easured using radiolabelled [C-14]-propionic acid. Errors, due to the binding of radioactive material to trub, were eliminated using silicon e oil centrifugation. Replication of analyses reduced the variations a ssociated with low cell counts during fermentation. Whilst fermenting brewer's wort, yeast intracellular pH values were maintained within a narrow range (5.9-6.4). Cellular ATP concentrations were highly conser ved in spite of the fact that the cells were exposed to an increasing concentration of ethanol as the fermentation progressed.