Dynamics of the Saccharomyces cerevisiae transcriptome during bread dough fermentation

Area of Science:

• Microbiology and Biotechnology
• Yeast Physiology and Fermentation

Background:

• Industrial yeast behavior is well-studied in liquid fermentation (beer, wine, bioethanol).
• Yeast physiology in solid-state fermentation (bread, cheese, cocoa) is less understood.
• Bread dough fermentation presents unique challenges for yeast cells.

Purpose of the Study:

• To investigate transcriptomic changes in Saccharomyces cerevisiae during bread dough fermentation.
• To identify key physiological responses and pathways involved in solid-state fermentation.
• To assess the role of the high-osmolarity glycerol (HOG) pathway in bread dough fermentation.

Main Methods:

• Transcriptome analysis of three distinct Saccharomyces cerevisiae strains in bread dough.
• Gene expression profiling at different fermentation time points.
• Gene deletion studies focusing on the HOG pathway components (e.g., HOG1).

Main Results:

• Consistent gene expression patterns observed across different yeast strains.
• Early fermentation: activation of glucose-regulated genes and osmotic stress response.
• Mid-fermentation: induction of amino acid metabolism genes.
• Late fermentation: activation of starvation and stress response pathways.
• High-osmolarity glycerol (HOG) pathway genes significantly upregulated at the onset.
• Deletion of HOG1 and related genes impaired yeast fermentation capacity.

Conclusions:

• Yeast cells in bread dough experience significant osmotic stress.
• The high-osmolarity glycerol (HOG) pathway plays a critical role in yeast adaptation and fermentation in solid matrices.
• Proper HOG pathway induction is essential for optimal bread dough fermentation.