Yeasts from Chinese strong flavour Daqu samples: isolation and evaluation of their potential for fortified Daqu production

In total, 16 yeast were isolated from Chinese strong flavour Daqu samples and underwent RAPD analysis and identification. Totally, 11 different species were identified among these isolates including Saccharomyces cerevisiae, Hanseniaspora vineae, Pichia kluyveri, Trichosporon asahii, Wickerhamomyces anomalus, Kluyveromyces lactis, Yarrowia lipolytica, Wickerhamomyces mori, Galactomyces geotrichum, Dabaryomyces hansenii, and Saccharomyces kudriavzevii. To understand the impact of these yeast strains on the quality and flavour of Daqu, we then assessed volatile compounds associated with Daqu samples fermented with corresponding strains. These analyses revealed strain YE006 exhibited the most robust ability to produce ethanol via fermentation but yielded relatively low quantities of volatile compounds, whereas strain YE010 exhibited relatively poor fermentation efficiency but produced the greatest quantity of volatile compounds. These two yeast strains were then utilized in a mixed culture to produce fortified Daqu, with the optimal inoculum size being assessed experimentally. These analyses revealed that maximal fermentation, saccharifying, liquefying, and esterifying power as well as high levels of volatile compounds were achieved when using a 2% inoculum composed of YE006/YE010 at a 1:2 (v/v) ratio. When the liquor prepared using this optimized fortified Daqu was compared to unfortified control Daqu, the former was found to exhibit significantly higher levels of flavour compounds and better sensory scores. Overall, our findings may provide a reliable approach to ensuring Daqu quality and improving the consistency and flavour of Chinese strong-flavour liquor through bioaugmentation.

Adaptive evolution of Saccharomyces cerevisiae and its application in co-culture with Saccharomyces kudriavzevii in the production of fermented Myrciaria jaboticaba

The objective of this work was to apply the adaptive evolution technique using the Saccharomyces cerevisiae T73 strain to increase its tolerance to ethanol and to evaluate its behavior in co-culture with Saccharomyces kudriavzevii CR85 in the production of fermented Myrciaria jaboticaba. Fermentations were carried out at 25 °C for 186 hours under agitation of 150 rpm, according to a central. The consumption of sugar, ethanol, glycerol and acetic acid formed during the fermentation process was evaluated. The results showed that there is an improvement in ethanol tolerance in S. cerevisiae T73 when submitted to the evolution process. Its use for the production of fermentation of Myrciaria jaboticaba in co-culture shows that the highest yield was observed when 0.0372 g.L-1 and 0.0648 g.L-1 of S. cerevisiae T73 PE (that underwent evolution) and CR85 respectively. These results differed statistically from the experiments using the original T73 strain. Regarding the production of ethanol in co-culture there is a significant increase when using the evolved T73 strain, showing possible changes in the primary metabolism of the ethanol production process, due to the changes promoted during the adaptive evolution of the T73 strain. The results show the potential of the new strain for the production of fermented with higher concentrations of sugars in the must.

Genomic instability in an interspecific hybrid of the genus Saccharomyces: a matter of adaptability

Ancient events of polyploidy have been linked to huge evolutionary leaps in the tree of life, while increasing evidence shows that newly established polyploids have adaptive advantages in certain stress conditions compared to their relatives with a lower ploidy. The genus Saccharomyces is a good model for studying such events, as it contains an ancient whole-genome duplication event and many sequenced Saccharomyces cerevisiae are, evolutionary speaking, newly formed polyploids. Many polyploids have unstable genomes and go through large genome erosions; however, it is still unknown what mechanisms govern this reduction. Here, we sequenced and studied the natural S. cerevisiae × Saccharomyces kudriavzevii hybrid strain, VIN7, which was selected for its commercial use in the wine industry. The most singular observation is that its nuclear genome is highly unstable and drastic genomic alterations were observed in only a few generations, leading to a widening of its phenotypic landscape. To better understand what leads to the loss of certain chromosomes in the VIN7 cell population, we looked for genetic features of the genes, such as physical interactions, complex formation, epistatic interactions and stress responding genes, which could have beneficial or detrimental effects on the cell if their dosage is altered by a chromosomal copy number variation. The three chromosomes lost in our VIN7 population showed different patterns, indicating that multiple factors could explain the mechanisms behind the chromosomal loss. However, one common feature for two out of the three chromosomes is that they are among the smallest ones. We hypothesize that small chromosomes alter their copy numbers more frequently as a low number of genes is affected, meaning that it is a by-product of genome instability, which might be the chief driving force of the adaptability and genome architecture of this hybrid.

Isolation, screening, identification and tolerance of yeast in cherry wine lees

In this study, yeast was isolated from cherry wine lees by rose Bengal medium, and its species was identified through three-stage screening, morphological observation and molecular biological identification. Moreover, the tolerance of screened strains was studied. The results showed that 30 strains of yeast were isolated from cherry wine lees, and five strains of yeast were selected, which were named YJN10, YJN16, YJN18, YJN19 and YJN28. After preliminary appraisal, strain YJN10 was Saccharomyces kudriavzevii, strain YJN16 was Saccharomyces paradoxus, and strains YJN18, YJN19, YJN28 were Saccharomyces cerevisiae. In the tolerance study, the tolerable sugar concentrations of the five strains were 650, 650, 550, 600 and 600 g/L. The tolerable alcohol volume fractions were 20, 20, 16, 18 and 18%. The tolerable molar concentration of potassium chloride was 1.8, 1.8, 1.5, 1.5 and 1.5 mol/L. Finally, strains YJN10, YJN16, YJN19 and YJN28 showed good tolerance, which laid a foundation for subsequent application in cherry wine fermentation.

Draft Genome Sequence of the Saccharomyces cerevisiae × Saccharomyces kudriavzevii HA1836 Interspecies Hybrid Yeast

ABSTRACT Saccharomyces cerevisiae × Saccharomyces kudriavzevii interspecies hybrid yeasts have frequently been isolated from alcoholic fermentation environments. Here, we report the draft genome sequence of the S. cerevisiae × S. kudriavzevii HA1836 strain isolated from grapes from an Austrian vineyard.