The use of H-2, He and O-2 during batch fermentation of Saccharomyces cerevisiae BRAS291 increased the final intracellular glycogen contents of the cells from 2-fold to 10-fold compared with a gas-free condition, and this depended on the gas applied. Differently, the intracellular trehalose contents increased from 2-fold to 10-fold in reducing conditions compared with more oxidizing conditions. During storage at 4 degrees C, the viability of cells cultivated with gas was twice that of cells cultivated without gas. These results could be explained by the intracellular carbohydrate contents as well as yeast ultrastructural modifications observed previously.