Response to environmental stresses is a key factor for microbial organism growth. One of the major stresses for yeasts in fermentative environments is ethanol.
is the most tolerant species in its ...genus, but intraspecific ethanol-tolerance variation exists. Although, much effort has been done in the last years to discover evolutionary paths to improve ethanol tolerance, this phenotype is still hardly understood. Here, we selected five strains with different ethanol tolerances, and used comparative genomics to determine the main factors that can explain these phenotypic differences. Surprisingly, the main genomic feature, shared only by the highest ethanol-tolerant strains, was a polysomic chromosome III. Transcriptomic data point out that chromosome III is important for the ethanol stress response, and this aneuploidy can be an advantage to respond rapidly to ethanol stress. We found that chromosome III copy numbers also explain differences in other strains. We show that removing the extra chromosome III copy in an ethanol-tolerant strain, returning to euploidy, strongly compromises its tolerance. Chromosome III aneuploidy appears frequently in ethanol-tolerance evolution experiments, and here, we show that aneuploidy is also used by natural strains to enhance their ethanol tolerance.
To remain competitive in increasingly overcrowded markets, yeast strain development programmes are crucial for fermentation-based food and beverage industries. In a winemaking context, there are many ...yeast phenotypes that stand to be improved. For example, winemakers endeavouring to produce sweet dessert wines wrestle with fermentation challenges particular to fermenting high-sugar juices, which can lead to elevated volatile acidity levels and extended fermentation times. In the current study, we used natural yeast breeding techniques to generate Saccharomyces spp. interspecific hybrids as a non-genetically modified (GM) strategy to introduce targeted improvements in important, wine-relevant traits. The hybrids were generated by mating a robust wine strain of Saccharomyces cerevisiae with a wine isolate of Saccharomyces bayanus, a species previously reported to produce wines with low concentrations of acetic acid. Two hybrids generated from the cross showed robust fermentation properties in high-sugar grape juice and produced botrytised Riesling wines with much lower concentrations of acetic acid relative to the industrial wine yeast parent. The hybrids also displayed suitability for icewine production when bench-marked against an industry standard icewine yeast, by delivering icewines with lower levels of acetic acid. Additionally, the hybrid yeast produced wines with novel aroma and flavour profiles and established that choice of yeast strain impacts on wine colour. These new hybrid yeasts display the desired targeted fermentation phenotypes from both parents, robust fermentation in high-sugar juice and the production of wines with low volatile acidity, thus establishing their suitability for wine styles that are traditionally troubled by excessive volatile acidity levels.
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CEKLJ, DOBA, EMUNI, GEOZS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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•Sterilised green coffee beans were fermented by two wine yeasts with or without Lc. lactis.•Yeast coculture of S. cerevisiae and P. kluyveri boosted ester content.•The mixed culture ...fermentations created coffee with pleasant fruit and winey aroma.•Lactococcus fermentation raised caramel aroma in roasted coffee.•Use of lactococcus with the yeast coculture further elevated the aroma-enhancing effect.
This study attempted to achieve coffee flavour biotransformation through controlled fermentation of sterilsed green coffee beans with a coculture of Saccharomyces cerevisiae and Pichia kluyveri (FYco) and a sequential inoculation of Lc. lactis subsp. cremoris and the yeast coculture (FLYco). Isoamyl acetate, 2-phenylethyl acetate, and ethyl octanoate were produced by 5.76, 1.35 and 0.54 mg/kg, respectively, in FYco fermented green coffee beans. Compared to the green coffee bean fermented by the yeast monocultures in previous study, FYco led to a 1.2- and 4.1-times elevation in production of isoamyl acetate and 2-phenylethyl acetate, respectively. FLYco further increased acetate ester production by more than 2 times relative to FYco. The esters produced in FYco and FLYco partially survived the roasting process and imparted the roasted coffees with considerable fruity and winey aromas. The lactic acid fermentation in FLYco increased the acidity in green coffee beans, which promoted the formation of caramel-smelling furfurals and preservation of acidity and sweetness in the roasted coffees. Apart from the mere additions of flavour modification from individual strains, the proper combination of multiple strains can result in synergistic effects that enhanced the modulating activities of individual strains and further enhance flavour complexity of the resulted coffee.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The aim of this work was to study the responses of Saccharomyces bayanus cells exposed to sub-lethal high-pressure homogenization (HPH) and determine whether the plasmatic membrane can sense HPH in ...the presence, or absence, of exogenous unsaturated fatty acids (UFAs) in the growth medium.
High-pressure homogenization damaged and caused the collapse of cell walls and membranes of a portion of cells; however, HPH did not significantly affect S. bayanus cell viability (less than 0.3 Log CFU ml(-1)). HPH strongly affected the membrane fatty acid (FA) composition by increasing the percentage of total UFA when compared with saturated fatty acids. The gene expression showed that the transcription of OLE1, ERG3, and ERG11 increased after HPH. The presence of exogenous UFA abolished HPH-induced effects on the OLE1 and ERG3 genes, increased the percentage of membrane lipids and decreased the expression of OLE1 and ERG3 within 30 min of treatment.
The results suggest a key role for UFA in the microbial cell response to sub-lethal stress. In addition, these data provide insight into the molecular basis of the response of S. bayanus to this innovative technology.
Elucidation of the mechanism of action for sub-lethal HPH will enable the utilization of this technology to modulate the starter performance at the industrial scale.
The specific impact of the yeast strain on the wine flavour and aroma has not been well characterised yet because this effect is usually combined with other variables during the winemaking. In this ...study, the contribution to wine flavour of two
Saccharomyces cerevisiae strains widely used in wine production, VIN13 and EC1118, was evaluated after fermentation at 15
°C. Chemical defined grape juice media fermented with the EC1118 strain showed higher solvent, fatty and pineapple aroma attributes, while that fermented with the VIN13 strain exhibited higher banana, fruity, yeasty and green attributes. Sensorial and chemical analyses evidenced that the production of flavour-active compounds is significantly affected by the yeast strain, as well as by the temperature of fermentation, as shown by comparing the former data with those from fermentations carried out at 28
°C under identical culture conditions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Grapes' infection by phytopathogenic fungi may often lead to rot and impair the quality and safety of the final product. Due to the concerns associated with the extensive use of chemicals to control ...these fungi, including their toxicity for environment and human health, bio-based products are being highly preferred, as eco-friendlier and safer alternatives. Specifically, yeasts have shown to possess antagonistic activity against fungi, being promising for the formulation of new biocontrol products.In this work 397 wine yeasts, isolated from Portuguese wine regions, were studied for their biocontrol potential against common grapes phytopathogenic fungal genera:
,
,
and
. This set comprised strains affiliated to 32 species distributed among 20 genera. Time-course monitoring of mold growth was performed to assess the inhibitory activity resulting from either diffusible or volatile compounds produced by each yeast strain. All yeasts displayed antagonistic activity against at least one of the mold targets.
was the most affected being strongly inhibited by 68% of the tested strains, followed by
(20%),
(19%) and
(7%). More notably, the approach used allowed the detection of a wide array of yeast-induced mold response profiles encompassing, besides the decrease of mold growth, the inhibition or delay of spore germination and the complete arrest of mycelial extension, and even its stimulation at different phases. Each factor considered (taxonomic affiliation, mode of action and fungal target) as well as their interactions significantly affected the antagonistic activity of the yeast isolates. The highest inhibitions were mediated by volatile compounds. Total inhibition of
was achieved by a strain of
, while the best performing yeasts against
,
and
, belong to
,
and
, respectively. Notwithstanding the wide diversity of yeasts tested, only three strains were found to possess a broad spectrum of antagonistic activity, displaying strong or very strong inhibition against the four fungal targets tested. Our results confirm the potential of wine yeasts as biocontrol agents, while highlighting the need for the establishment of fit-for-purpose selection programs depending on the mold target, the timing, and the mode of application.
Non-
Saccharomyces yeasts are metabolically active during spontaneous and inoculated must fermentations, and by producing a plethora of by-products, they can contribute to the definition of the wine ...aroma. Thus, use of
Saccharomyces and non-
Saccharomyces yeasts as mixed starter cultures for inoculation of wine fermentations is of increasing interest for quality enhancement and improved complexity of wines. We initially characterized 34 non-
Saccharomyces yeasts of the genera
Candida,
Lachancea (
Kluyveromyces),
Metschnikowia and
Torulaspora, and evaluated their enological potential. This confirmed that non-
Saccharomyces yeasts from wine-related environments represent a rich sink of unexplored biodiversity for the winemaking industry. From these, we selected four non-
Saccharomyces yeasts to combine with starter cultures of
Saccharomyces cerevisiae in mixed fermentation trials. The kinetics of growth and fermentation, and the analytical profiles of the wines produced indicate that these non-
Saccharomyces strains can be used with
S. cerevisiae starter cultures to increase polysaccharide, glycerol and volatile compound production, to reduce volatile acidity, and to increase or reduce the total acidity of the final wines, depending on yeast species and inoculum ratio used. The overall effects of the non-
Saccharomyces yeasts on fermentation and wine quality were strictly dependent on the
Saccharomyces/non-
Saccharomyces inoculum ratio that mimicked the differences of fermentation conditions (natural or simultaneous inoculated fermentation).
► Widespread biodiversity within non-Saccharomyces wine yeasts. ► Mixed fermentation with selected non-Saccharomyces wine yeasts may improve wine quality. ► The modulation of inoculum determines the influence of non-Saccharomyces yeast. ► Interactions in mixed culture fermentations should be further investigated.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Saccharomyces cerevisiae isolates from grapes, soil, vine bark and buds collected at seven phenological stages of an annual growth cycle, were molecular typed by Microsatellite Multiplex PCR. ...Subsequently 30 S. cerevisiae genotypes were selected and the effect of vineyard environmental stressors, in both sublethal upper and lower levels, on their growth parameters was evaluated. The effect of low and high temperature (7–40 °C), pH (2.5–8.0), glucose concentration (3.0–300.0 g/L), nitrogen concentration (0.008–8.0 g/L), and copper presence (24 mg/L) were modelled individually using the reparametrized Gompertz equation. Multivariate ANOVA and Generalized Procrustes Analysis were used to determine the environmental stressor's influence over the lag phase (λ) and the maximum specific growth rate (μmax). Both parameters were significantly affected by the S. cerevisiae genotype, the treatments, and the interaction between them. Despite a generalized reduction in μmax and a variable answer in λ, the 30 S. cerevisiae genotypes were able to overcome all the treatments. Extreme glucose limitation, copper presence and low temperature had the highest impact over the growth parameters. Interestingly, ten genotypes mostly distributed in the vineyard were the least affected, suggesting a greater acclimatization fitness and the possibility to persist in the changing conditions of the vine annual cycle.
•Growth parameters A, λ and μmax are genotype and stress treatments dependent.•Copper and low temperature stresses produce the most diverse response in the strains.•Ten repeatedly isolated genotypes showed better acclimatization in the vineyard.•Strains' phenotypic diversity would allow them to acclimatize in the vineyard.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
AIMS: In the present study, it was investigated the antagonistic behaviour of Metschnikowia pulcherrima, as biocontrol agent, against the main wine yeast species involved in the winemaking process. ...METHODS AND RESULTS: Seven strains of M. pulcherrima were evaluated for the antimicrobial activity against 114 yeast strains belonging to Pichia, Candida, Hanseniaspora, Kluyveromyces, Saccharomycodes, Torulaspora, Brettanomyces and Saccharomyces genera. Results showed both different inter‐generic and intra‐generic responses to the antimicrobial action of M. pulcherrima strains. Interestingly, the antimicrobial activity of M. pulcherrima did not have any influence on the growth of Saccharomyces cerevisiae. Instead, M. pulcherrima displayed a broad and effective antimicrobial action on undesired wild spoilage yeasts, such as Brettanomyces/Dekkera, Hanseniaspora and Pichia genera. Fermentation trials carried out in synthetic grape must confirmed the antimicrobial activity of M. pulcherrima, determining the early death of the non‐Saccharomyces co‐inoculated cultures. CONCLUSIONS: The antimicrobial activity of M. pulcherrima does not seem due to proteinaceous compounds such as killer phenomenon, but to the pulcherriminic acid (the precursor of pulcherrimin pigment) that depletes iron present in the medium, making it not available to the other yeasts. SIGNIFICANCE AND IMPACT OF THE STUDY: These data agree with and further support the potential use of selected M. pulcherrima strains in controlled multistarter fermentations with S. cerevisiae starter cultures.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Abstract
Wine fermentations are dominated by Saccharomyces yeast. However, dozens of non-Saccharomyces yeast genera can be found in grape musts and in the early and intermediate stages of wine ...fermentation, where they co-exist with S. cerevisiae. The diversity of non-Saccharomyces species is determinant for the sensorial attributes of the resulting wines, both directly (by producing aroma impact compounds) and indirectly (modulating the performance of Saccharomyces). Many research groups worldwide are exploring the great diversity of wine yeasts to exploit their metabolic potential to improve wine flavor or to prevent wine spoilage. In this work, we share a new data set from a wide ITS amplicon survey of 272 wine samples, and we perform a preliminary exploration to build a catalogue of 242 fungal and yeast genera detectable in wine samples, estimating global figures of their prevalence and relative abundance patterns across wine samples. Thus, our mycobiome survey provides a broad measure of the yeast diversity potentially found in wine fermentations; we hope that the wine yeast research community finds it useful, and we also want to encourage further discussion on the advantages and limitations that meta-taxonomic studies may have in wine research and industry.
Wine fermentations harbor a higher-than-expected yeast diversity that deserves to be explored.
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