3. Results and Discussion
Yeast strains were pre-growing in YPD (2% glucose, 2% peptone, 1% yeast extract power), and then
switched into corn juice. To choose the best determining time point of intracellular trehalose, the growth
curve of yeast strains in corn juice were investigated first. As shown in Figure 1, the logarithmic phases of the
yeasts were all from 12 to 20h. So we choose this time period to investigate the levels of intracellular
trehalose. And the cultivation conditions of yeast strains were 13 Brix corn juice medium, 30 , 170 r/min.
Figure 2 showed clearly that the yeast strains could accumulate trehalose in the logarithmic phase. For the
growth condition became unfavorable to yeast with time, such as nutrient consumption, changes of PH, the
generation of metabolic waste and so on, then trehalose was accumulated to help them against bad
environment and at last reached a peak at the end of logarithmic phase. This was in consistence with previous
study[21], which proved that the survival rate of S. cerevisiae in stationary phase (with high trehalose
accumulation) was higher than in the logarithmic phase. In the following study, the level of trehalose was
investigated at 20th.
Hypertonic conditions could improve the transcriptional level of TPS1 and TPS2. So the influence of
different concentration of salt to the accumulation of trehalose was studied. Figure 3 suggested that the level
3. Results and Discussion
Yeast strains were pre-growing in YPD (2% glucose, 2% peptone, 1% yeast extract power), and then
switched into corn juice. To choose the best determining time point of intracellular trehalose, the growth
curve of yeast strains in corn juice were investigated first. As shown in Figure 1, the logarithmic phases of the
yeasts were all from 12 to 20h. So we choose this time period to investigate the levels of intracellular
trehalose. And the cultivation conditions of yeast strains were 13 Brix corn juice medium, 30 , 170 r/min.
Figure 2 showed clearly that the yeast strains could accumulate trehalose in the logarithmic phase. For the
growth condition became unfavorable to yeast with time, such as nutrient consumption, changes of PH, the
generation of metabolic waste and so on, then trehalose was accumulated to help them against bad
environment and at last reached a peak at the end of logarithmic phase. This was in consistence with previous
study[21], which proved that the survival rate of S. cerevisiae in stationary phase (with high trehalose
accumulation) was higher than in the logarithmic phase. In the following study, the level of trehalose was
investigated at 20th.
Hypertonic conditions could improve the transcriptional level of TPS1 and TPS2. So the influence of
different concentration of salt to the accumulation of trehalose was studied. Figure 3 suggested that the level
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