Functional genomic analysis of commercial baker's yeast during initial stages of model dough-fermentation. Food Microbiol 23: 717-728
Fukui Prefectural University, Фукуй, Fukui, Japan Food Microbiology
(Impact Factor: 3.33).
01/2007; 23(8):717-28. DOI: 10.1016/j.fm.2006.02.003
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.
Available from: Hugo Diego Sánchez
- "Occurs mainly, alcoholic type, slightly acidic, and its action is predictable and reproducible under appropriate conditions of manufacturing . This yeast has been the most studied, and have identified genes responsible for the production of various metabolites of fermentation as the ethyl alcohol . The use of natural yeast is one of the oldest processes in the production of breads. "
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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.
Available from: Jun Shima
- "The composition of the liquid fermentation medium was the same as that described in previous reports (Tanaka et al., 2006; Tanaka-Tsuno et al., 2007), except that the sucrose concentration was 27.8% and the maltose concentration was 2.78%. "
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ABSTRACT: During bread-making processes, yeast cells are exposed to various baking-associated stresses. High-sucrose concentrations exert severe osmotic stress that seriously damages cellular components by generation of reactive oxygen species (ROS). Previously, we found that the accumulation of proline conferred freeze-thaw stress tolerance and the baker's yeast strain that accumulated proline retained higher-level fermentation abilities in frozen doughs than the wild-type strain. In this study, we constructed self-cloning diploid baker's yeast strains that accumulate proline. These resultant strains showed higher cell viability and lower intracellular oxidation levels than that observed in the wild-type strain under high-sucrose stress condition. Proline accumulation also enhanced the fermentation ability in high-sucrose-containing dough. These results demonstrate the usefulness of proline-accumulating baker's yeast for sweet dough baking.
Available from: Barbara Dunn
- "Vitamin B1 forms the cofactor thiamin pyrophosphate , which is essential for sugar utilization by S. cerevisiae, in particular for sugar fermentation (Bataillon et al. 1996; Hohmann and Meacock 1998; Mojzita and Hohmann 2006). Indeed, several reports have shown significant up-regulation of thiamin metabolism genes in fermenting yeast cells in various industrial settings including wine, sake, and bread dough (Rossignol et al. 2003; Tanaka et al. 2006; Wu et al. 2006), and in yeast cells cultivated in sugarcane molasses (Shima et al. 2005), indicating that there is a high demand for thiamin (and its precursors) under these industrial conditions. However, it is well known that for S. cerevisiae, as well as for other members of the Saccharomyces sensu stricto complex, the presence of thiamin in the medium has a negative effect on the initial growth phase of the yeast cells, although it does not affect the final cell density (Minami et al. 1982; Nakamura et al. 1982; Kamihara and Nakamura 1984). "
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ABSTRACT: Fuel ethanol is now a global energy commodity that is competitive with gasoline. Using microarray-based comparative genome hybridization (aCGH), we have determined gene copy number variations (CNVs) common to five industrially important fuel ethanol Saccharomyces cerevisiae strains responsible for the production of billions of gallons of fuel ethanol per year from sugarcane. These strains have significant amplifications of the telomeric SNO and SNZ genes, which are involved in the biosynthesis of vitamins B6 (pyridoxine) and B1 (thiamin). We show that increased copy number of these genes confers the ability to grow more efficiently under the repressing effects of thiamin, especially in medium lacking pyridoxine and with high sugar concentrations. These genetic changes have likely been adaptive and selected for in the industrial environment, and may be required for the efficient utilization of biomass-derived sugars from other renewable feedstocks.
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