Characterization of a Torulaspora delbrueckii diploid strain with optimized performance in sweet and frozen sweet dough
ABSTRACT Torulaspora delbrueckii is a baker's yeast that is highly tolerant to freeze-thaw stress, making it suitable for frozen dough technology. The T. delbrueckii strain PYCC5321, isolated from traditional bread dough, combines this tolerance with a high degree of ionic and osmotic stress resistance. However, the industrial use of this strain for frozen and sweet frozen baking is hampered by its small cell size, which causes clogging problems at the filtering stage. Here, we report the construction of a stable diploid strain of T. delbrueckii PYCC5321, which we named Td21-2n. The new strain was more than 2.7-fold bigger than their haploid counterpart, whereas biomass yield, stress resistance and sweet dough leavening ability were found to be similar in both strains. Moreover, the gassing power of the diploid after dough freezing also remained unaltered. Thus, Td21-2n meets the requirements necessary for industrial production and is suitable for application in frozen sweet baking products.
- SourceAvailable from: Warren Albertin
[Show abstract] [Hide abstract]
- "T.delbrueckii was formerly described as a haploid species –, because of its small cell size and also because tetrads are rarely observed following sporulation. However, several lines of evidence suggest that T. delbrueckii may not be haploid: first, the recent genome sequencing of type strain CBS 1146 reveals that, at the genetic level, T. delbrueckii possesses apparently functional mating-type (MAT) locus and silent HMR and HML loci, suggesting this species could be homothallic . "
ABSTRACT: The yeast Torulaspora delbrueckii is associated with several human activities including oenology, bakery, distillery, dairy industry, etc. In addition to its biotechnological applications, T. delbrueckii is frequently isolated in natural environments (plant, soil, insect). T. delbrueckii is thus a remarkable ubiquitous yeast species with both wild and anthropic habitats, and appears to be a perfect yeast model to search for evidence of human domestication. For that purpose, we developed eight microsatellite markers that were used for the genotyping of 110 strains from various substrates and geographical origins. Microsatellite analysis showed four genetic clusters: two groups contained most nature strains from Old World and Americas respectively, and two clusters were associated with winemaking and other bioprocesses. Analysis of molecular variance (AMOVA) confirmed that human activities significantly shaped the genetic variability of T. delbrueckii species. Natural isolates are differentiated on the basis of geographical localisation, as expected for wild population. The domestication of T. delbrueckii probably dates back to the Roman Empire for winemaking (∼1900 years ago), and to the Neolithic era for bioprocesses (∼4000 years ago). Microsatellite analysis also provided valuable data regarding the life-cycle of the species, suggesting a mostly diploid homothallic life. In addition to population genetics and ecological studies, the microsatellite tool will be particularly useful for further biotechnological development of T. delbrueckii strains for winemaking and other bioprocesses.PLoS ONE 04/2014; 9(4):e94246. DOI:10.1371/journal.pone.0094246 · 3.23 Impact Factor
[Show abstract] [Hide abstract]
- "This hypothesis is supported by our knowledge on freeze tolerance which is expected to be higher in smaller cells. Freezing tolerance has been related to cell size in S. cerevisiae [27,28], Torulaspora delbrueckii , Candida utilis, Escherichia coli, Lactobacillus plantarum, and the human leukemia K562 cells  and may have driven the evolution towards "ant" life-history strategy. A physical explanation could be that the larger surface-to-volume ratio of the small cells makes easier the release of water out of the cell and the decrease of intracellular pressure. "
ABSTRACT: Variation of resource supply is one of the key factors that drive the evolution of life-history strategies, and hence the interactions between individuals. In the yeast Saccharomyces cerevisiae, two life-history strategies related to different resource utilization have been previously described in strains from different industrial origins. In this work, we analyzed metabolic traits and life-history strategies in a broader collection of yeast strains sampled in various ecological niches (forest, human body, fruits, laboratory and industrial environments). By analysing the genetic and plastic variation of six life-history and three metabolic traits, we showed that S. cerevisiae populations harbour different strategies depending on their ecological niches. On one hand, the forest and laboratory strains, referred to as extreme "ants", reproduce quickly, reach a large carrying capacity and a small cell size in fermentation, but have a low reproduction rate in respiration. On the other hand, the industrial strains, referred to as extreme "grasshoppers", reproduce slowly, reach a small carrying capacity but have a big cell size in fermentation and a high reproduction rate in respiration. "Grasshoppers" have usually higher glucose consumption rate than "ants", while they produce lower quantities of ethanol, suggesting that they store cell resources rather than secreting secondary products to cross-feed or poison competitors. The clinical and fruit strains are intermediate between these two groups. Altogether, these results are consistent with a niche-driven evolution of S. cerevisiae, with phenotypic convergence of populations living in similar habitat. They also revealed that competition between strains having contrasted life-history strategies ("ants" and "grasshoppers") seems to occur at low frequency or be unstable since opposite life-history strategies appeared to be maintained in distinct ecological niches.BMC Evolutionary Biology 12/2009; 9:296. DOI:10.1186/1471-2148-9-296 · 3.41 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: During the bread-making process, industrial baker's yeast cells are exposed to multiple baking-associated stresses, such as elevated high-temperature, high-sucrose and freeze–thaw stresses. There is a high demand for baker's yeast strains that could withstand these stresses with high leavening ability. The SNR84 gene encodes H/ACA snoRNA (small nucleolar RNA), which is known to be involved in pseudouridylation of the large subunit rRNA. However, the function of the SNR84 gene in baker's yeast coping with baking-associated stresses remains unclear. In this study, we explored the effect of SNR84 overexpression on baker's yeast which was exposed to high-temperature, high-sucrose and freeze–thaw stresses. These results suggest that overexpression of the SNR84 gene conferred tolerance of baker's yeast cells to high-temperature, high-sucrose and freeze–thaw stresses and enhanced their leavening ability in high-sucrose and freeze–thaw dough. These findings could provide a valuable insight for breeding of novel stress-resistant baker's yeast strains that are useful for baking.International Journal of Food Microbiology 03/2015; 197. DOI:10.1016/j.ijfoodmicro.2014.12.014 · 3.16 Impact Factor