Functional genomic analysis of commercial baker's yeast during initial stages of model dough-fermentation.
ABSTRACT Gene expression profiles of baker's yeast during initial dough-fermentation were investigated using liquid fermentation (LF) media to obtain insights at the molecular level into rapid adaptation mechanisms of baker's yeast. Results showed that onset of fermentation caused drastic changes in gene expression profiles within 15 min. Genes involved in the tricarboxylic acid (TCA) cycle were down-regulated and genes involved in glycolysis were up-regulated, indicating a metabolic shift from respiration to fermentation. Genes involved in ethanol production (PDC genes and ADH1), in glycerol synthesis (GPD1 and HOR2), and in low-affinity hexose transporters (HXT1 and HXT3) were up-regulated at the beginning of model dough-fermentation. Among genes up-regulated at 15 min, several genes classified as transcription were down-regulated within 30 min. These down-regulated genes are involved in messenger RNA splicing and ribosomal protein biogenesis and in transcriptional regulator (SRB8, MIG1). In contrast, genes involved in amino acid metabolism and in vitamin metabolism, such as arginine biosynthesis, riboflavin biosynthesis, and thiamin biosynthesis, were subsequently up-regulated after 30 min. Interestingly, the genes involved in the unfolded protein response (UPR) pathway were also subsequently up-regulated. Our study presents the first overall description of the transcriptional response of baker's yeast during dough-fermentation, and will thus help clarify genomic responses to various stresses during commercial fermentation processes.
SourceAvailable from: Hugo Diego Sánchez
Article: Mother dough in bread making[Show abstract] [Hide abstract]
ABSTRACT: The objective of this work was the preparation of mother dough and to study the effect produced on bread, besides to look for the kind of bread that best reflects the effect of using sourdough. pH and acidity were measured to sourdough without replenish during 7 days at 5ºC and to sourdough with replenishment every 24 hours, during 27 days at 5ºC. Breads were made applying both the French and the pan bread methods. Experts scored the external and internal characteristics of breads. When the sourdough is maintained at 5ºC and replenished every 24 hours, its stabilization is achieved at the day 10 with a pH of 4.40 and an acidity of 6.5 mass meq/100 g. By other hand, when the sourdough is maintained at 5ºC but is not replenished every 24 hours, pH and acidity are constant up to the day 3 and then a very important change is produced. The addition of 10% of mother dough improves quality of crumb structure and flavor in the French type bread while there is not an improved quality of the pan bread. Therefore, the French type bread is the kind of bread that best reflects the effect of using mother dough.
[Show abstract] [Hide abstract]
ABSTRACT: Direct bonding without the use of any adhesives was demonstrated on quartz glasses, YAG and Ti:sapphire crystals. The bonded region of Ti:sapphire was evaluated from the macroscopic to the atomic level by four different methods.
[Show abstract] [Hide abstract]
ABSTRACT: The behavior of yeast cells during industrial processes such as the production of beer, wine and bioethanol has been extensively studied. By contrast, our knowledge about yeast physiology during solid-state processes, such as bread dough, cheese or cocoa fermentation remains limited. We investigated changes in the transcriptome of three genetically distinct Saccharomyces cerevisiae strains during bread dough fermentation. Our results show that regardless of the genetic background, all three strains exhibit similar changes in expression patterns. At the onset of fermentation, expression of glucose-regulated genes changes dramatically, and the osmotic stress response is activated. The middle fermentation phase is characterized by the induction of genes involved in amino acid metabolism. Finally, at the latest time point, cells suffer from nutrient depletion and activate pathways associated with starvation and stress response. Further analysis shows that genes regulated by the High Osmolarity Glycerol (HOG) pathway, the major pathway involved in the response to osmotic stress and glycerol homeostasis, are among the most differentially expressed genes at the onset of fermentation. More importantly, deletion of HOG1 and other genes of this pathway significantly reduces fermentation capacity. Together, our results demonstrate that cells embedded in a solid matrix such as bread dough suffer severe osmotic stress, and that a proper induction of the HOG pathway is critical for an optimal fermentation.Applied and Environmental Microbiology 09/2013; DOI:10.1128/AEM.02649-13 · 3.95 Impact Factor