Advancements in Life Sciences, vol.8, no.1, pp.47-51, 2020 (Peer-Reviewed Journal)
The fermentation of sugars into ethanol even in the presence of oxygen is referred to as the
Crabtree effect. The yeast cells displaying Crabtree effect are indicated as Crabtree-positive yeast.
Saccharomyces cerevisiae is Crabtree positive and Debaryomyces occidentalis is Crabtree-negative
yeast which does not have Crabtree effect. The reserve carbohydrate metabolism is different in Crabtree-positive
and Crabtree-negative yeast cells. The present study aimed to determine the trehalose and glycogen
accumulation patterns both in Crabtree-positive and Crabtree-negative yeast species.
Methods: In this research, trehalose and glycogen contents of S. cerevisiae and D. occidentalis yeast species
were examined in a time course manner in three different carbon sources: glucose, galactose and glycerol.
Firstly, yeast cells were grown in rich media supplemented with glucose then all washed and switched to fresh
cultures including glucose, galactose and glycerol.
Results: In S. cerevisiae yeast cells the overnight accumulated trehalose degraded very rapidly after nonfermentable carbon source replenishment, but this took place in a long time, nearly two days, in D. occidentalis
yeast cells. However, whenever D. occidentalis yeast cells shifted to glycerol, all the accumulated trehalose
degraded within the twelve hours. Glycogen accumulation in D. occidentalis yeast cells is lower than S.
cerevisiae yeast cells both in fermentable and non-fermentable carbon sources.
Conclusion: Results indicated that glycogen and trehalose accumulation patterns are completely different in D.
occidentalis than S. cerevisiae. Crabtree-negative yeast cells generally, prefer to accumulate glycogen instead
of trehalose as reserve carbohydrate. But in our research we proved that Crabtree-negative yeast D.
occidentalis, accumulates more trehalose than S. cerevisiae yeast cells in non-fermentable carbon sources.