Abstract
BackgroundRecent years have seen a huge growth in the market of industrial yeasts with the need for strains affording better performance or to be used in new applications. Stress tolerance of commercial Saccharomyces cerevisiae yeasts is, without doubt, a trait that needs improving. Such trait is, however, complex, and therefore only in-depth knowledge of their biochemical, physiological and genetic principles can help us to define improvement strategies and to identify the key factors for strain selection.ResultsWe have determined the transcriptional response of commercial baker's yeast cells to both high-sucrose and lean dough by using DNA macroarrays and liquid dough (LD) model system. Cells from compressed yeast blocks display a reciprocal transcription program to that commonly reported for laboratory strains exposed to osmotic stress. This discrepancy likely reflects differences in strain background and/or experimental design. Quite remarkably, we also found that the transcriptional response of starved baker's yeast cells was qualitatively similar in the presence or absence of sucrose in the LD. Nevertheless, there was a set of differentially regulated genes, which might be relevant for cells to adapt to high osmolarity. Consistent with this, overexpression of CAF16 or ORC2, two transcriptional factor-encoding genes included in this group, had positive effects on leavening activity of baker's yeast. Moreover, these effects were more pronounced during freezing and frozen storage of high-sucrose LD.ConclusionsEngineering of differentially regulated genes opens the possibility to improve the physiological behavior of baker's yeast cells under stress conditions like those encountered in downstream applications.
Highlights
Recent years have seen a huge growth in the market of industrial yeasts with the need for strains affording better performance or to be used in new applications
We compared the genome-wide transcription pattern of starved cells from compressed yeast blocks with that of cells cultured for 60 min in high-sugar liquid dough (LD)
We demonstrated that this flour-free model system mimics the nutritional and stressful environment encountered by baker's yeast cells in bread dough [11]
Summary
Recent years have seen a huge growth in the market of industrial yeasts with the need for strains affording better performance or to be used in new applications. Proofing times are longer for sweet bakery loaves and yield low volume products To face these problems, manufacturers use greater amounts of yeast in the dough for-. 400 genes, covering a wide variety of physiological functions, including carbon and amino acid metabolism, redox balance, anti-oxidant protection, ATPases, membrane proteins, chaperones, cytoskeletal and cell wall adaptations [5,6,7]. Such information has helped identify target genes, regulators and pathways involved in osmotic response [3]. Given the special characteristics of these strains, it is questionable whether such data can be used to develop molecular strategies to improve osmotic stress resistance in industrial yeasts
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