VIABILITY OF CANDIDA SHEHATAE IN D-XYLOSE FERMENTATIONS WITH ADDED ETHANOL

Ethanol was added at concentrations of 25 and 50 g/L to active cultures of Candida shehatae under oxygen-limited (fermentative) conditions. Added ethanol completely inhibited growth and fermentation Of D-xylose by C. shehatae. Cultures with added ethanol rapidly declined in cell viability as measured by plate counts and methylene blue staining. The rate of decline in cell viability was dependent on the amount of added ethanol. Over the course of the fermentation, cell viability, as measured by plate counts, was significantly lower in all experiments (with or without ethanol addition) compared with the viability measurements by methylene blue staining. Thus, data from the plate counts provided a more sensitive measure of the toxic effects of added ethanol and long-term anaerobiosis on C. shehatae growth/fermentation. Mean cell volume and total cell volume declined in fermentations with added ethanol.