Global expression studies in baker's yeast reveal target genes for the improvement of industrially-relevant traits: the cases of CAF16 and ORC2

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.

Improving industrial yeast strains: exploiting natural and artificial diversity

“…Hence, the development of more robust strains that are still capable of producing a high-quality end product is a prime focus in biotechnology (Kim et al ., 1996; Perez-Torrado et al ., 2002, 2010; Panadero et al ., 2007; Kaino et al ., 2008; Gomez-Pastor et al ., 2012). For example, using an inverse metabolic engineering approach, Perez-Torrado et al .…”

“…For example, using an inverse metabolic engineering approach, Perez-Torrado et al . (2010) identified two genes, CAF19 and ORC2 , important for osmotolerance. Overexpression of these genes exerted a positive impact on the leavening activity of baker's yeast.…”

“…Inverse metabolic engineering has already yielded various industrial strains (cf. infra; Bro et al, 2005;Blieck et al, 2007;Rossouw et al, 2008;Yoshida et al, 2008;Perez-Torrado et al, 2010;Duong et al, 2011). A clear example of how inverse metabolic engineering can be applied to target complex phenotypes is a study by Rossouw et al (2008).…”

Dynamics of the Saccharomyces cerevisiae Transcriptome during Bread Dough Fermentation

“…This is at least partly due to the technical difficulties associated with isolating representative cell samples from the solid fermentation matrix. Some studies have attempted to gain insight into bread fermentation by mimicking the process in liquid (15)(16)(17). Whereas such studies definitely contributed to our knowledge, they change the single most important parameter of SSFs (the solid state) and are therefore not an optimal model for the industrial SSF process.…”

“…Several studies have investigated the expression profile of yeast genes during liquid fermentation such as beer, wine, or even liquid model dough fermentation (15,16,(18)(19)(20)(21)(22)(23). Those studies showed that in general, the start of fermentation is associated with a loss of stress resistance due to the repression of stress-related genes by glucose or sucrose (24)(25)(26).…”