Molecular mechanisms of freeze injuries in commercial bakers yeast

Frozen dough baking is useful method in the modern bread-making industry. However, the fermentation activity of bakers yeast dramatically decreased after thawing due to freeze injuries, because bakers yeast cells contained in dough experience freeze injuries during freeze-thaw processes. Here, we performed genome-wide expression analysis to determine genetic response in bakers yeasts under freeze-thaw condition using a DNA microarray analysis. Functional and clustering analyses in gene expression reveal that genes could be characterized by the term of freeze-thaw stress. Under short-term freeze stress (freeze treatment for 3 day), genes involved in ribosomal protein were up-regulated. Under long-term freeze stress (freeze treatment for longer than 7 day), genes involved in energy synthesis were up-regulated. In each phase, genes involved in protein damage, several stresses and trehalose and glycogen metabolism were also up-regulated. Through these freeze stress, yeast cells may improve reduced efficiency of translation and enhanced cell protection mechanism to survive under freeze stress condition. These regulations of these genes would be controlled by the cAMP-protein kinase A pathway.

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