In the last few years there is an increasing interest on the use of mixed fermentation of Saccharomyces and non-Saccharomyces wine yeasts for inoculation of wine fermentations to enhance the quality ...and improve complexity of wines. In the present work Lachancea (Kluyveromyces) thermotolerans and Saccharomyces cerevisiae were evaluated in simultaneous and sequential fermentation with the aim to enhance acidity and improve the quality of wine.
In this specific pairing of yeast strains in mixed fermentations (S. cerevisiae EC1118 and L. thermotolerans 101), this non-Saccharomyces yeast showed a high level of competitiveness. Nevertheless the S. cerevisiae strain dominated the fermentation over the spontaneous S. cerevisiae strains also under the industrial fermentation conditions.
The different condition tested (modalities of inoculum, temperature of fermentation, different grape juice) influenced the specific interactions and the fermentation behaviour of the co-culture of S. cerevisiae and L. thermotolerans. However, some metabolic behaviours such as pH reduction and enhancement of 2-phenylethanol and glycerol, were shown here under all of the conditions tested.
The specific chemical profiles of these wines were confirmed by the sensory analysis test, which expressed these results at the tasting level as significant increases in the spicy notes and in terms of total acidity increases.
► Lachancea thermotolerans mixed with Saccharomyces cerevisiae reduce pH and enhance 2-phenylethanol, glycerol. ► Inoculum, temperature, grape juices influence the mixed fermentation behaviour. ► Tasting tests of industrial fermentations show different sensorial profiles of wines.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Wine microbiota is a dense and diverse ecosystem that is directly involved in the production and synthesis of many metabolites of oenological interest thereby directly affecting wine composition. The ...biodiversity and successional evolution of yeast and lactic acid bacteria (LAB) species and strains within species during alcoholic (AF) and malolactic fermentation (MLF) is greatly influenced by the complexity of the wine environment. Consequently, the successful prediction of wine characteristics is limited.
The use of starter cultures has allowed better control of the fermentation process and the production of wines with desired characteristics. Mixed culture fermentations with selected non-Saccharomyces and Saccharomyces yeasts has regained attention in recent years due to their potential to modulate a wide range of metabolites of oenological interest. In this context, interactions among yeast species and LAB throughout the AF and MLF are known to influence the main enological parameters and aromatic profile of the wines. Studies have been conducted to uncover the nature of these interactions, with the aim to better control the AF and MLF.
This review provides an overview of microorganism interactions during the different steps of the winemaking process. This gives wine producers the ability to control and fine-tune microorganism population dynamics and therefore the fermentation process and finally wine quality.
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•Wine microbiota are directly involved in the synthesis of many metabolites of oenological interest.•Mixed fermentations with non-Saccharomyces and Saccharomyces yeasts benefits wine quality.•Interactions among microorganisms influence the wine profile but limited knowledge of these interactions are available.•Understanding how yeasts and lactic acid bacteria interact enables better control of wine fermentation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Saccharomyces cerevisiae and grape juice are ‘natural companions’ and make a happy wine marriage. However, this relationship can be enriched by allowing ‘wild’ non‐Saccharomyces yeast to participate ...in a sequential manner in the early phases of grape must fermentation. However, such a triangular relationship is complex and can only be taken to ‘the next level’ if there are no spoilage yeast present and if the ‘wine yeast’ – S. cerevisiae – is able to exert its dominance in time to successfully complete the alcoholic fermentation. Winemakers apply various ‘matchmaking’ strategies (e.g. cellar hygiene, pH, SO₂, temperature and nutrient management) to keep ‘spoilers’ (e.g. Dekkera bruxellensis) at bay, and allow ‘compatible’ wild yeast (e.g. Torulaspora delbrueckii, Pichia kluyveri, Lachancea thermotolerans and Candida/Metschnikowia pulcherrima) to harmonize with potent S. cerevisiae wine yeast and bring the best out in wine. Mismatching can lead to a ‘two is company, three is a crowd’ scenario. More than 40 of the 1500 known yeast species have been isolated from grape must. In this article, we review the specific flavour‐active characteristics of those non‐Saccharomyces species that might play a positive role in both spontaneous and inoculated wine ferments. We seek to present ‘single‐species’ and ‘multi‐species’ ferments in a new light and a new context, and we raise important questions about the direction of mixed‐fermentation research to address market trends regarding so‐called ‘natural’ wines. This review also highlights that, despite the fact that most frontier research and technological developments are often focussed primarily on S. cerevisiae, non‐Saccharomyces research can benefit from the techniques and knowledge developed by research on the former.
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BFBNIB, FZAB, GIS, IJS, KILJ, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Abstract
Hanseanispora species, including H. guilliermondii, are long known to be abundant in wine grape-musts and to play a critical role in vinification by modulating, among other aspects, the wine ...sensory profile. Despite this, the genetics and physiology of Hanseniaspora species remains poorly understood. The first genomic sequence of a H. guilliermondii strain (UTAD222) and the discussion of its potential significance are presented in this work. Metabolic reconstruction revealed that H. guilliermondii is not equipped with a functional gluconeogenesis or glyoxylate cycle, nor does it harbours key enzymes for glycerol or galactose catabolism or for biosynthesis of biotin and thiamine. Also, no fructose-specific transporter could also be predicted from the analysis of H. guilliermondii genome leaving open the mechanisms underlying the fructophilic character of this yeast. Comparative analysis involving H. guilliermondii, H. uvarum, H. opuntiae and S. cerevisiae revealed 14 H. guilliermondii-specific genes (including five viral proteins and one β-glucosidase). Furthermore, 870 proteins were only found within the Hanseniaspora proteomes including several β-glucosidases and decarboxylases required for catabolism of biogenic amines. The release of H. guilliermondii genomic sequence and the comparative genomics/proteomics analyses performed, is expected to accelerate research focused on Hanseniaspora species and to broaden their application in the wine industry and in other bio-industries in which they could be explored as cell factories.
The yeast Saccharomyces cerevisiae synthesises a variety of volatile aroma compounds during wine fermentation. In this study, the influence of fermentation temperature on (1) the production of ...yeast-derived aroma compounds and (2) the expression of genes involved in aroma compounds' metabolism (ADH1, PDC1, BAT1, BAT2, LEU2, ILV2, ATF1, ATF2, EHT1 and IAH1) was assessed, during the fermentation of a defined must at 15 and 28°C. Higher concentrations of compounds related to fresh and fruity aromas were found at 15°C, while higher concentrations of flowery related aroma compounds were found at 28°C. The formation rates of volatile aroma compounds varied according to growth stage. In addition, linear correlations between the increases in concentration of higher alcohol and their corresponding acetates were obtained. Genes presented different expression profiles at both temperatures, except ILV2, and those involved in common pathways were co-expressed (ADH1, PDC1 and BAT2; and ATF1, EHT1 and IAH1). These results demonstrate that the fermentation temperature plays an important role in the wine final aroma profile, and is therefore an important control parameter to fine-tune wine quality during winemaking.
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CEKLJ, DOBA, EMUNI, FZAB, GEOZS, IJS, IMTLJ, IZUM, KILJ, KISLJ, 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 with S. cerevisiae or P. kluyveri.•Fermentations led to direct and indirect sensory modulation in roasted coffees.•The yeast ...fermentations raised fruity aroma in roasted coffee through ester production.•S. cerevisiae fermentation also elevated nutty aroma in the roasted coffee.
Direct fermentations of sterilised green coffee beans by monocultures of Saccharomyces cerevisiae and Pichia kluyveri were investigated for coffee flavour biotransformation. During fermentation, fruity esters were generated in the green coffee beans by yeasts. 2-Phenylethyl acetate was elevated by 1.1 mg/kg and 0.03 mg/kg in P. kluyveri- and S. cerevisiae-fermented green beans, respectively, as compared to the untreated sample. Ethyl octanoate (0.51 mg/kg) and isoamyl acetate (1.69 mg/kg) only existed in S. cerevisiae- and P. kluyveri-fermented green beans, respectively. After roasting, higher levels of 2-phenylethyl acetate were detected in fermented coffees, and ethyl octanoate was found only in the S. cerevisiae-fermented sample, despite the loss of isoamyl acetate in P. kluyveri-fermented coffees during roasting. The fruity esters generated by the yeasts during green coffee bean fermentations were directly transferred to the volatile profiles formed after roasting and enhanced the fruity attribute in the roasted coffees, with a more noticeable effect observed from S. cerevisiae fermentation. Higher productions of N-heterocyclic volatiles occurred during roasting of S. cerevisiae-fermented coffees and contributed to elevated nutty and roasted aromas. S. cerevisiae and P. kluyveri are considered suitable starter cultures for controlled coffee flavour biotransformation through controlled fermentations of green coffee beans.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Surveys conducted worldwide have shown that a significant proportion of grape musts are suboptimal for yeast nutrients, especially assimilable nitrogen. Nitrogen deficiencies are linked to slow and ...stuck fermentations and sulphidic off-flavour formation. Nitrogen supplementation of grape musts has become common practice; however, almost no information is available on the effects of nitrogen supplementation on wine flavour. In this study, the effect of ammonium supplementation of a synthetic medium over a wide range of nitrogen values on the production of volatile and non-volatile compounds by two high-nitrogen-demand wine fermentation strains of Saccharomyces cerevisiae was determined. To facilitate this investigation, a simplified chemically defined medium that resembles the nutrient composition of grape juice was used. Analysis of variance revealed that ammonium supplementation had significant effects on the concentration of residual sugar, L-malic acid, acetic acid and glycerol but not the ethanol concentration. While choice of yeast strain significantly affected half of the aroma compounds measured, nitrogen concentrations affected 23 compounds, including medium-chain alcohols and fatty acids and their esters. Principal component analysis showed that branched-chain fatty acids and their esters were associated with low nitrogen concentrations, whereas medium-chain fatty esters and acetic acid were associated with high nitrogen concentrations.
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CEKLJ, DOBA, EMUNI, FZAB, GEOZS, IJS, IMTLJ, IZUM, KILJ, KISLJ, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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.
Saccharomyces cerevisiae is a highly fermentative species able to complete the wine fermentation. However, the interaction with other non-Saccharomyces yeasts can determine the fermentation ...performance of S. cerevisiae. We have characterised three rare non-Saccharomyces yeasts (Cyberlindnera fabianii, Kazachstania unispora and Naganishia globosa), studying their impact on S. cerevisiae fitness and wine fermentation performance. Using a wide meta-taxonomic dataset of wine samples, analysed through ITS amplicon sequencing, we show that about a 65.07% of wine samples contains Naganishia spp., a 27.21% contains Kazachstania spp., and only a 4.41% contains Cyberlindnera spp; in all cases with average relative abundances lower than 1% of total fungal populations. Although the studied N. globosa strain showed a limited growth capacity in wine, both K. unispora and C. fabianii showed a similar growth phenotype to that of S. cerevisiae in different fermentation conditions, highlighting the outstanding growth rate values of K. unispora. In mixed fermentations with S. cerevisiae, the three yeast species affected co-culture growth parameters and wine chemical profile (volatile compounds, polysaccharides and proteins). K. unispora DN201 strain presents an outstanding capacity to compete with S. cerevisiae strains during the first stage of wine fermentation, causing stuck fermentations in both synthetic and natural grape musts.
•The prevalence of Cyberlindnera spp. in wine populations is about 4% of samples.•The prevalence of Kazachstania spp. in wine populations is about 27% of samples.•The prevalence of Naganishia spp. in wine populations is about 65% of samples.•Kazachstania unispora DN201 caused stuck fermentations.•K.unispora DN201 has high nitrogen consumption rate and production of acetic acid.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
At high cell density or under low nutrient conditions, yeasts collectively adapt their metabolism by secreting aromatic alcohols in what is known as quorum sensing. However, the mechanisms and role ...of quorum sensing in yeast are poorly understood, and the methodology behind this process is not well established. This paper describes an effective approach to study quorum sensing in yeast fermentations. The separation, detection, and quantification of the putative quorum-sensing molecules 2-phenylethanol, tryptophol, and tyrosol have been optimized on a simple HPLC-based system. With the use of a phenyl HPLC column and a fluorescence detector, the sensitivity of the system was significantly increased. This allowed extraction and concentration procedures to be eliminated and the process to be scaled down to 2 mL minifermentations. Additionally, an innovative method for rapid viable-cell counting is presented. This study forms the basis for detailed studies in kinetics and regulation of quorum sensing in yeast fermentation.
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IJS, KILJ, NUK, PNG, UL, UM, UPUK
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