Yeast strains dominant

Yeasts tend to dominate the initial phase of the natural fermentation of cocoa pulp [1]. An isolate oiKluyveromyces marxianus (CCT 3172) was found to be the most pectinolytic of 12 yeast strains, resulting in degradation of pulp cell walls [1]. 

The spontaneous fermentation of dry white wines in the same vineyard is also carried out by the same dominant yeast strains in all of the barrels. 

The spontaneous microfiora of S. cerevisiae seems to fiuctuate. At present, the factors involved in this fluctuation have not been identified. In a given vineyard, spontaneous fermentation is not systematically carried out by the same strains each year strain specificity does not exist and therefore does not participate in vineyard characteristics. Ecological observations do not confirm the notion of a vineyard-specific yeast. Furthermore, some indigenous strains, dominant in a given vineyard, have been found in other nearby or distant vineyards. For example, the Fzlb2-89 strain, isolated for the first time in a vineyard in Pessac-Ldognan, was later identified not only in the spontaneous fermentation of dry white and red wines of other vineyards in the same appellation, but also in relatively distant wineries as far away as the Mddoc. This strain has since been selected and commercialized under the name Zymaflore FIO. 

However, in the same grape must, interactions also depend on the strains. LAB growth can be much easier in the wines which are made when certain yeast strains are dominant (Fomachon 1968). Yeasts differences can be attributed to many factors such as the production of varying levels of SO and fatty acids as well as specific proteinaceous molecules and mannoproteins. The last two compounds should act as inhibitors (Comitini et al. 2005) or activators, respectively (Diez et al. 2010). 

This is what occurred to those strains of S. cerevisiae selected for traditional vinification processes (whether a commercial starter and not) that have been tested for the production of sweet wines, such as Picolit (Urso et al., 2008) and Vin Santo wine (Domizio et al., 2008) here, they were not able to dominate the relative fermentation process. On the contrary, Unican Sherry yeast, which is normally used for the production... 

As noted earlier, the yeast Saccharomyces, an Important experimental organism, can exist in either a haploid or a diploid state. In these unicellular eukaryotes, crosses between haploid cells can determine whether a mutant allele is dominant or recessive. Haploid yeast cells, which carry one copy of each chromosome, can be of two different mating types known as a and a. Haploid cells of opposite mating type can mate to produce a/a diploids, which carry two copies of each chromosome. If a new mutation with an observable phenotype is Isolated in a haploid strain, the mutant strain can be mated to a wild-type strain of the opposite mating type to produce a/a diploids that are heterozygous for the mutant allele. If these diploids exhibit the mutant trait, then the mutant allele is dominant, but if the diploids appear as wild-type, then the mutant allele is recessive. When a/a diploids are placed under starvation conditions, the cells... 

The [PSP] element is inherited in an orderly, reproducible way but one that is different from most genetic traits (Fig. 1) (Cox, 1965). When a haploid [PSP] strain is mated to a haploid [psi strain, the resulting diploid has a suppression phenotype that is, [PSP] is dominant. On sporulation, however, none of the haploid progeny are [psir] as would be expected for a nuclear determinant Instead, [PSP] is transmitted to all haploid progeny. (The capital letters in [PSP] signify dominance the brackets signify nonchromosomal inheritance.) This unusual pattern of inheritance was partly explained by later experiments that localized the [PS7+] determinant to the cytoplasm (Cox et al, 1980 Fink and Conde, 1976). Surprisingly, however, the [PSP] phenotype could not be linked to any of tbe known cytoplasmic nucleic acids in yeast (Cox et al, 1988 Serio and Lindquist, 1999). 

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