Impact of oxygenation on the performance of three non-Saccharomyces yeasts in co-fermentation with Saccharomyces cerevisiae

Effect of Hanseniaspora vineae and Saccharomyces cerevisiae co-fermentations on aroma compound production in beer

In recent years, the boom of the craft beer industry refocused the biotech interest from ethanol production to diversification of beer aroma profiles. This study analyses the fermentative phenotype of a collection of non-conventional yeasts and examines their role in creating new flavours, particularly through co-fermentation with industrial Saccharomyces cerevisiae. High-throughput solid and liquid media fitness screening compared the ability of eight Saccharomyces and four non-Saccharomyces yeast strains to grow in wort. We determined the volatile profile of these yeast strains and found that Hanseniaspora vineae displayed a particularly high production of the desirable aroma compounds ethyl acetate and 2-phenethyl acetate. Given that H. vineae on its own can't ferment maltose and maltotriose, we carried out mixed wort co-fermentations with a S. cerevisiae brewing strain at different ratios. The two yeast strains were able to co-exist throughout the experiment, regardless of their initial inoculum, and the increase in the production of the esters observed in the H. vineae monoculture was maintained, alongside with a high ethanol production. Moreover, different inoculum ratios yielded different aroma profiles: the 50/50 S. cerevisiae/H. vineae ratio produced a more balanced profile, while the 10/90 ratio generated stronger floral aromas. Our findings show the potential of using different yeasts and different inoculum combinations to tailor the final aroma, thus offering new possibilities for a broader range of beer flavours and styles.

A comparative study of Lachancea thermotolerans fermentative performance under standardized wine production conditions

The study explores diverse strains of Lachancea thermotolerans in single-inoculum wine fermentation conditions using synthetic grape must. It aims to analyze the role of the species without external influences like other microorganisms or natural grape must variability. Commercial strains and selected vineyard isolates, untested together previously, are assessed. The research evaluates volatile and non-volatile chemical compounds in final wine, revealing significant strain-based variations. L. thermotolerans notably produces lactic acid and consumes malic acid, exhibiting moderate ethanol levels. The volatile profile displays strain-specific impacts, affecting higher alcohol and ester concentrations compared to S. cerevisiae. These effects vary based on the specific compounds. Using a uniform synthetic must enables direct strain comparisons, eliminating grape-related, environmental, or timing variables in the experiment, facilitating clearer insights into the behavior of L. thermotolerans in wine fermentation. The study compares for the first time all available commercial strains of L. thermotolerans.

Competition for Nitrogen Resources: An Explanation of the Effects of a Bioprotective Strain Metschnikowia pulcherrima on the Growth of Hanseniaspora Genus in Oenology

As a biological alternative to the antimicrobial action of SO2, bioprotection has been proposed to winemakers as a means to limit or prevent grape musts microbial alteration. Competition for nitrogenous nutrients and for oxygen are often cited as potential explanations for the effectiveness of bioprotection. This study analyses the effect of a bioprotective M. pulcherrima strain on the growth of one H. valbyensis strain and one H. uvarum strain. Bioprotection efficiency was observed only against H. valbyensis inoculated at the two lowest concentrations. These results indicate a potential species-dependent efficiency of the bioprotective strain and a strong impact of the initial ratio between bioprotective and apiculate yeasts. The analysis of the consumption of nitrogen compounds revealed that leucine, isoleucine, lysine and tryptophan were consumed preferentially by all three strains. The weaker assimilation percentages of these amino acids observed in H. valbyensis at 24 h growth suggest competition with M. pulcherrima that could negatively affects the growth of the apiculate yeast in co-cultures. The slowest rate of O2 consumption of H. valbyensis strain, in comparison with M. pulcherrima, was probably not involved in the bioprotective effect. Non-targeted metabolomic analyses of M. pulcherrima and H. valbyensis co-culture indicate that the interaction between both strains particularly impact lysin and tryptophan metabolisms.

Bioprotection Efficiency of Metschnikowia Strains in Synthetic Must: Comparative Study and Metabolomic Investigation of the Mechanisms Involved

Three Metschnikowia strains marketed as bioprotection yeasts were studied to compare their antimicrobial effect on a mixture of two Hanseniaspora yeast strains in synthetic must at 12 °C, mimicking pre-fermentative maceration by combining different approaches. The growth of the different strains was monitored, their nitrogen and oxygen requirements were characterised, and their metabolomic footprint in single and co-cultures studied. Only the M. fructicola strain and one M. pulcherrima strains colonised the must and induced the rapid decline of Hanseniaspora. The efficiency of these two strains followed different inhibition kinetics. Furthermore, the initial ratio between Metschnikowia and Hanseniaspora was an important factor to ensure optimal bioprotection. Nutrient consumption kinetics showed that apiculate yeasts competed with Metschnikowia strains for nutrient accessibility. However, this competition did not explain the observed bioprotective effect, because of the considerable nitrogen content remaining on the single and co-cultures. The antagonistic effect of Metschnikowia on Hanseniaspora probably implied another form of amensalism. For the first time, metabolomic analyses of the interaction in a bioprotection context were performed after the pre-fermentative maceration step. A specific footprint of the interaction was observed, showing the strong impact of the interaction on the metabolic modulation of the yeasts, especially on the nitrogen and vitamin pathways.

Fate of carbon in synthetic media fermentations containing Metschnikowia pulcherrima or Meyerozyma guilliermondii in the presence and absence of Saccharomyces cerevisiae

While sequentially inoculating non-Saccharomyces yeasts with Saccharomyces cerevisiae can lower the alcohol contents of wine, the abilities of these yeasts to utilize/produce ethanol or generate other byproducts remained unclear. Metschnikowia pulcherrima or Meyerozyma guilliermondii were inoculated into media with or without S. cerevisiae to assess byproduct formation. Both species metabolized ethanol in a yeast-nitrogen-base medium but produced the alcohol in a synthetic grape juice medium. In fact, Mt. pulcherrima and My. guilliermondii generated less ethanol per gram of metabolized sugar (0.372 and 0.301 g/g, respectively) compared to S. cerevisiae (0.422 g/g). Sequentially inoculating each non-Saccharomyces species with S. cerevisiae into grape juice media achieved up to 3.0% v/v alcohol reduction compared to S. cerevisiae alone while producing variable glycerol, succinic acid, and acetic acid concentrations. However, neither non-Saccharomyces yeasts released appreciable CO₂ under fermentative conditions regardless of incubation temperature. Despite equivalent peak populations, S. cerevisiae produced more biomass (2.98 g/L) than the non-Saccharomyces yeasts while sequential inoculations yielded higher biomass with Mt. pulcherrima (3.97 g/L) but not My. guilliermondii (3.03 g/L). To reduce ethanol concentrations, these non-Saccharomyces species may metabolize ethanol and/or produce less from metabolized sugars compared to S. cerevisiae but also divert carbon towards glycerol, succinic acid, and/or biomass.

Bio-protection in oenology by Metschnikowia pulcherrima: from field results to scientific inquiry

Finding alternatives to the use of chemical inputs to preserve the sanitary and organoleptic quality of food and beverages is essential to meet public health requirements and consumer preferences. In oenology, numerous manufacturers already offer a diverse range of bio-protection yeasts to protect must against microbiological alterations and therefore limit or eliminate sulphites during winemaking. Bio-protection involves selecting non-Saccharomyces yeasts belonging to different genera and species to induce negative interactions with indigenous microorganisms, thereby limiting their development and their impact on the matrix. Although the effectiveness of bio-protection in the winemaking industry has been reported in numerous journals, the underlying mechanisms are not yet well understood. The aim of this review is to examine the current state of the art of field trials and laboratory studies that demonstrate the effects of using yeasts for bio-protection, as well as the interaction mechanisms that may be responsible for these effects. It focuses on the yeast Metschnikowia pulcherrima, particularly recommended for the bio-protection of grape musts.

Effect of Metschnikowia pulcherrima on Saccharomyces cerevisiae PDH By-Pass in MixedFermentation with Varied Sugar Concentrations of Synthetic Grape Juice and Inoculation Ratios

The effects of Metschnikowia pulcherrima and high glucose osmolality on S. cerevisiae pyruvate dehydrogenase pathway (PDH) by-pass were examined by varying the starting sugar concentration of synthetic grape juice and the inoculation ratio of S. cerevisiae to M. pulcherrima. The findings revealed that M. pulcherrima and osmolarity impacted S. cerevisiae’s PDH by-pass. The inoculation concentration of M. pulcherrima significantly affected pyruvate decarboxylase (PDC) activity and acs2 expression when the initial sugar concentration was 200 g L−1 and 290 g L−1. The osmolarity caused by the initial sugar (380 g L−1) significantly influenced the enzymatic activity of S. cerevisiae, which decreased PDC and acetaldehyde dehydrogenase (ALD) activities while increasing Acetyl-CoA synthetase (ACS) activity. The reduction in acetic acid in the wine was caused by M. pulcherrima altering the initial sugar concentration faced by S. cerevisiae, which in turn affected enzymatic activity. The alteration of enzyme activity and accumulation of primary metabolites revealed why mixed fermentation could reduce the acetic acid content in wine by altering the enzymatic activity and affecting the expression of several key genes. The M. pulcherrima inoculation levels had no significant effect on the acetic acid and glycerol concentration in the same fermentation medium.

Multiparametric Approach to Interactions between Saccharomyces cerevisiae and Lachancea thermotolerans during Fermentation

The aim of a significant part of current wine technology research is to better understand and monitor mixed culture fermentations and optimize the microbiological processes and characteristics of the final wine. In this context, the yeast couple formed by Lachancea thermotolerans and Saccharomyces cerevisiae is of particular interest. The diverse results observed in the literature have shown that wine characteristics are dependent on both interactions between yeasts and environmental and fermentation parameters. Here, we took a multiparametric approach to study the impact of fermentation parameters on three different but related aspects of wine fermentation: population dynamics, fermentation, and volatile compound production. An experimental design was used to assess the effects of four independent factors (temperature, oxygenation, nitrogen content, inoculum ratio) on variables representing these three aspects. Temperature and, to a lesser extent, oxygenation and the inoculum ratio, were shown to constitute key factors in optimizing the presence of Lachancea thermotolerans during fermentation. The inoculum ratio also appeared to greatly impact lactic acid production, while the quantity of nitrogen seemed to be involved more in the management of aroma compound production. These results showed that a global approach to mixed fermentations is not only pertinent, but also constitutes an important tool for controlling them.

Species-Dependent Metabolic Response to Lipid Mixtures in Wine Yeasts

Lipids are essential energy storage compounds and are the core structural elements of all biological membranes. During wine alcoholic fermentation, the ability of yeasts to adjust the lipid composition of the plasma membrane partly determines their ability to cope with various fermentation-related stresses, including elevated levels of ethanol and the presence of weak acids. In addition, the lipid composition of grape juice also impacts the production of many wine-relevant aromatic compounds. Several studies have evaluated the impact of lipids and of their metabolism on fermentation performance and aroma production in the dominant wine yeast Saccharomyces cerevisiae, but limited information is available on other yeast species. Thus, the aim of this study was to evaluate the influence of specific fatty acid and sterol mixtures on various non-Saccharomyces yeast fermentation rates and the production of primary fermentation metabolites. The data show that the response to different lipid mixtures is species-dependent. For Metschnikowia pulcherrima, a slight increase in carbon dioxide production was observed in media enriched with unsaturated fatty acids whereas Kluyveromyces marxianus fermented significantly better in synthetic media containing a higher concentration of polyunsaturated fatty acids than monounsaturated fatty acids. Torulaspora delbrueckii fermentation rate increased in media supplemented with lipids present at an equimolar concentration. The data indicate that these different responses may be linked to variations in the lipid profile of these yeasts and divergent metabolic activities, in particular the regulation of acetyl-CoA metabolism. Finally, the results suggest that the yeast metabolic footprint and ultimately the wine organoleptic properties could be optimized via species-specific lipid adjustments.

Making wine in Pañul’s craft pottery vessels: a first approach in the study of the dynamic of alcoholic fermentation and wine volatile composition

Traditional winemaking in amphora-like clay vessels is one of the oldest known methods of wine production. Currently, some wine producers have readopted traditional winemaking methods to generate unique attributes that differentiate their products raising regional wine typicity. The aim of this research was to study the dynamic of alcoholic fermentation and volatile composition of ‘Carignan’ wines fermented into Pañul’s clay vessels and comparing them with the wines vinified into stainless-steel tanks. Density curve of the musts contained in the Pañul’s pottery vessels followed a similar trend than in the samples contained in the stainless-steel tanks. The temperatures of the must and the cap during alcoholic fermentation were lower in the Pañul’s pottery vessels than in the stainless-steel tanks in most of the evaluated days. Thus, clay vessels may provide temperature-regulating properties beneficing wine fermentation compared to stainless-steel tanks. Pañul’s clay vessels produced wines with higher terpenes, β-ionone and 2-phenylethyl alcohol content, and lower values of some individual higher alcohols, isoamyl acetate, lactones, and pH than the stainless-steel tanks. Therefore, the results suggest that Pañul’s pottery vessels favored increasing the terpene alcohols and other volatile compounds concentrations, in addition to decreasing certain higher alcohols and acetate esters contents such as benzyl alcohol and iso-amyl acetate. These outcomes may be of interest to ceramic producers and wine producers since they open a range of economic opportunities to diversify their products.

Phenotypic characterization of cell-to-cell interactions between two yeast species during alcoholic fermentation

Microbial multispecies ecosystems are responsible for many biotechnological processes and are particularly important in food production. In wine fermentations, in addition to the natural microbiota, several commercially relevant yeast species may be co-inoculated to achieve specific outcomes. However, such multispecies fermentations remain largely unpredictable because of multilevel interactions between naturally present and/or co-inoculated species. Understanding the nature of such interactions has therefore become essential for successful implementation of such strategies. Here we investigate interactions between strains of Saccharomyces cerevisiae and Lachancea thermotolerans. Co-fermentations with both species sharing the same bioreactor (physical contact) were compared to co-fermentations with physical separation between the species in a membrane bioreactor ensuring free exchange of metabolites. Yeast culturability, viability and the production of core metabolites were monitored. The previously reported negative interaction between these two yeast species was confirmed. Physical contact greatly reduced the culturability and viability of L. thermotolerans and led to earlier cell death, compared to when these yeasts were co-fermenting without cell-cell contact. In turn, in the absence of cell-cell contact, L. thermotolerans metabolic activity led to an earlier decline in culturability in S. cerevisiae. Cell-cell contact did not result in significant differences in the major fermentation metabolites ethanol, acetic acid and lactic acid, but impacted on the production of some volatile compounds.

Evaluation of Autochthonous Non-Saccharomyces Yeasts by Sequential Fermentation for Wine Differentiation in Galicia (NW Spain)

Non-Saccharomyces yeasts constitute a useful tool in winemaking because they secrete hydrolytic enzymes and produce metabolites that enhance wine quality; in addition, their ability to reduce alcohol content and/or to increase acidity can help to mitigate the effects of climatic change on wines. The purpose of this study was to evaluate the oenological traits of non-Saccharomyces yeast strains autochthonous from Galicia (NW Spain). To do that, we carried out sequential fermentation using 13 different species from the yeast collection of Estación de Viticultura e Enoloxía de Galicia (Evega) and Saccharomyces cerevisiae EC1118. The fermentation kinetics and yeast implantation were monitored using conventional methods and genetic techniques, respectively. The basic chemical parameters of wine were determined using the OIV official methodology, and the fermentative aroma compounds were determined by GC–FID. The results evidenced the limited fermentative power of these yeasts and the differences in their survival after the addition of S. cerevisiae to complete fermentation. Some strains reduced the alcohol and/or increased the total acidity of the wine. The positive effect on sensory wine properties as well as the production of desirable volatile compounds were confirmed for Metschnikowia spp. (Mf278 and Mp176), Lachancea thermotolerans Lt93, and Pichia kluyveri Pkl88. These strains could be used for wine diversification in Galicia.

Understanding Wine through Yeast Interactions

Wine is a product of microbial activities and microbe–microbe interactions. Yeasts are the principal microorganisms responsible for the evolution and fulfillment of alcoholic fermentation. Several species and strains coexist and interact with their environment and with each other during the fermentation course. Yeast–yeast interactions occur even from the early stages of fermentation, determining yeast community structure and dynamics during the process. Different types of microbial interactions (e.g., mutualism and commensalism or competition and amensalism) may exert positive or negative effects, respectively, on yeast populations. Interactions are intimately linked to yeast metabolic activities that influence the wine analytical profile and shape the wine character. In this context, much attention has been given during the last years to the interactions between Saccharomyces cerevisiae (SC) and non-Saccharomyces (NS) yeast species with respect to their metabolic contribution to wine quality. Yet, there is still a significant lack of knowledge on the interaction mechanisms modulating yeast behavior during mixed culture fermentation, while much less is known about the interactions between the various NS species or between SC and Saccharomyces non-cerevisiae (SNC) yeasts. There is still much to learn about their metabolic footprints and the genetic mechanisms that alter yeast community equilibrium in favor of one species or another. Gaining deeper insights on yeast interactions in the grape–wine ecosystem sets the grounds for understanding the rules underlying the function of the wine microbial system and provides means to better control and improve oenological practices.

Mechanisms Involved in Interspecific Communication between Wine Yeasts

In parallel with the development of non-Saccharomyces starter cultures in oenology, a growing interest has developed around the interactions between the microorganisms involved in the transformation of grape must into wine. Nowadays, it is widely accepted that the outcome of a fermentation process involving two or more inoculated yeast species will be different from the weighted average of the corresponding individual cultures. Interspecific interactions between wine yeasts take place on several levels, including interference competition, exploitation competition, exchange of metabolic intermediates, and others. Some interactions could be a simple consequence of each yeast running its own metabolic programme in a context where metabolic intermediates and end products from other yeasts are present. However, there are clear indications, in some cases, of specific recognition between interacting yeasts. In this article we discuss the mechanisms that may be involved in the communication between wine yeasts during alcoholic fermentation.

Growth of Non-Saccharomyces Native Strains under Different Fermentative Stress Conditions

The selection of yeast strains adapted to fermentation stresses in their winegrowing area is a key factor to produce quality wines. Twelve non-Saccharomyces native strains from Denomination of Origin (D.O.) “Vinos de Madrid” (Spain), a warm climate winegrowing region, were tested under osmotic pressure, ethanol, and acidic pH stresses. In addition, mixed combinations between non-Saccharomyces and a native Saccharomyces cerevisiae strain were practised. Phenotypic microarray technology has been employed to study the metabolic output of yeasts under the different stress situations. The yeast strains, Lachancea fermentati, Lachancea thermotolerans, and Schizosaccharomyces pombe showed the best adaptation to three stress conditions examined. The use of mixed cultures improved the tolerance to osmotic pressure by Torulaspora delbrueckii, S. pombe, and Zygosaccharomyces bailii strains and to high ethanol content by Candida stellata, S. pombe, and Z. bailii strains regarding the control. In general, the good adaptation of the native non-Saccharomyces strains to fermentative stress conditions makes them great candidates for wine elaboration in warm climate areas.

Comparative evaluation of package types in alleviating textural softening and package-swelling of Paocai during storage: Insight into microbial invasion, cell wall pectinolysis and alteration in sugar and organic acid profiles

The present study aimed to investigate the effect of initial vacuum package (VP), air package (AP) and salt-solution package (NP) on texture softening and package-swelling of Paocai by comparing the changes in physicochemical properties, pectinolysis, microstructure, microbial profile, as well as sugar and organic acid profiles during storage. Results showed that, when compared with AP and NP, with suppressive microbial invasion and less total pectinase activity, VP could retain more soluble pectin and induce more compact microstructure of Paocai, leading to higher hardness of Paocai during storage. As for package-swelling, VP mitigated gas-production in package by changing the microbial composition and metabolic patterns of sugar and organic acid in Paocai, especially targeted regulating the abundance of genus Kazachstania. This study provided a perspective for appropriate packaging technology to control the pectinase activity as well as cell-invading and gas-producing microorganisms for manufacturing fermented vegetable with better texture and non-package-swelling.

Effect of Aeration on Yeast Community Structure and Volatile Composition in Uninoculated Chardonnay Wines

Uninoculated wines are regarded as having improved mouthfeel and texture and more complex flavor profiles when compared to wines inoculated with commercial S. cerevisiae strains. Uninoculated fermentation involves a complex microbial succession of yeasts and bacteria during fermentation. Microbial population dynamics are affected by several factors that can ultimately determine if a particular species or strain contributes to wine aroma and flavor. In this work, we have studied the effect of aeration, a common winemaking practice, on the yeast microbiota during uninoculated Chardonnay wine fermentation. The timing of aeration and then aeration intensity were evaluated across two successive vintages. While the timing of aeration significantly impacted fermentation efficiency across oxygen treatments, different levels of aeration intensity only differed when compared to the non-aerated control ferments. Air addition increased the viable cell population size of yeast from the genera Hanseniaspora, Lachancea, Metschnikowia and Torulaspora in both vintages. While in 2019, a high relative abundance was found for Hanseniaspora species in aerated ferments, in 2020, T. delbrueckii was visibly more abundant than other species in response to aeration. Accompanying the observed differences in yeast community structure, the chemical profile of the finished wines was also different across the various aeration treatments. However, excessive aeration resulted in elevated concentrations of ethyl acetate and acetic acid, which would likely have a detrimental effect on wine quality. This work demonstrates the role of aeration in shaping yeast population dynamics and modulating a volatile profile in uninoculated wines, and highlights the need for careful air addition to avoid a negative sensory impact on wine flavor and aroma.

The metabolism of lipids in yeasts and applications in oenology

Lipids are valuable compounds present in all living organisms, which display an array of functions related to compartmentalization, energy storage and enzyme activation. Furthermore, these compounds are an integral part of the plasma membrane which is responsible for maintaining structure, facilitating the transport of solutes in and out of the cell and cellular signalling necessary for cell survival. The lipid composition of the yeast Saccharomyces cerevisiae has been extensively investigated and the impact of lipids on S. cerevisiae cellular functions during wine alcoholic fermentation is well documented. Although other yeast species are currently used in various industries and are receiving increasing attention in winemaking, little is known about their lipid metabolism. This review article provides an extensive and critical evaluation of our knowledge on the biosynthesis, accumulation, metabolism and regulation of fatty acids and sterols in yeasts. The implications of the yeast lipid content on stress resistance as well as performance during alcoholic fermentation are discussed and a particular emphasis is given on non-Saccharomyces yeasts. Understanding lipid requirements and metabolism in non-Saccharomyces yeasts may lead to a better management of these yeast to enhance their contributions to wine properties.

Measurement Techniques to Resolve and Control Population Dynamics of Mixed-Culture Processes

Microbial mixed cultures are gaining increasing attention as biotechnological production systems, since they offer a large but untapped potential for future bioprocesses. Effects of secondary metabolite induction and advantages of labor division for the degradation of complex substrates offer new possibilities for process intensification. However, mixed cultures are highly complex, and, consequently, many biotic and abiotic parameters are required to be identified, characterized, and ideally controlled to establish a stable bioprocess. In this review, we discuss the advantages and disadvantages of existing measurement techniques for identifying, characterizing, monitoring, and controlling mixed cultures and highlight promising examples. Moreover, existing challenges and emerging technologies are discussed, which lay the foundation for novel analytical workflows to monitor mixed-culture bioprocesses.

The non-Saccharomyces yeast Pichia kluyveri for the production of aromatic volatile compounds in alcoholic fermentation

Alcoholic fermentation is influenced by yeast strain, culture media, substrate concentration and fermentation conditions, which contribute to taste and aroma. Some non-Saccharomyces yeasts are recognized as volatile compound producers that enrich aromatic profile of alcoholic beverages. In this work, 21 strains of Pichia kluyveri isolated from different fermentative processes and regions were evaluated. A principal component analysis (PCA) showed statistical differences between strains mainly associated with the variety and concentration of the compounds produced. From the PCA, two strains (PK1 and PK8) with the best volatile compound production were selected to evaluate the impact of culture media (M12 medium and Agave tequilana juice), stirring speeds (100 and 250 rpm) and temperatures (20°C, 25°C and 30°C). Increased ester production was observed at 250 rpm. Greatest effect in alcohols and ester production was found with A. tequilana, identifying PK1 as higher alcohol producer, and PK8 as better ester producer. Regarding temperature, PK1 increased ester production with decreased fermentation temperature. PK8 presented maximum levels of ethyl acetate and ethyl dodecanoate at 20°C, and finally isoamyl acetate increased its production at 30°C. Therefore, P. kluyveri strains are of great interest to produce different aromatic profiles that are affected by factors including medium, agitation and temperature.

Flavor Formation in Chinese Rice Wine (Huangjiu): Impacts of the Flavor-Active Microorganisms, Raw Materials, and Fermentation Technology

Huangjiu (Chinese rice wine) has been consumed for centuries in Asian countries and is known for its unique flavor and subtle taste. The flavor compounds of Huangjiu are derived from a wide range of sources, such as raw materials, microbial metabolic activities during fermentation, and chemical reactions that occur during aging. Of these sources, microorganisms have the greatest effect on the flavor quality of Huangjiu. To enrich the microbial diversity, Huangjiu is generally fermented under an open environment, as this increases the complexity of its microbial community and flavor compounds. Thus, understanding the formation of flavor compounds in Huangjiu will be beneficial for producing a superior flavored product. In this paper, a critical review of aspects that may affect the formation of Huangjiu flavor compounds is presented. The selection of appropriate raw materials and the improvement of fermentation technologies to promote the flavor quality of Huangjiu are discussed. In addition, the effects of microbial community composition, metabolic function of predominant microorganisms, and dynamics of microbial community on the flavor quality of Huangjiu are examined. This review thus provides a theoretical basis for manipulating the fermentation process by using selected microorganisms to improve the overall flavor quality of Huangjiu.

The transcriptomic response of a wine strain of Lachancea thermotolerans to oxygen deprivation

The yeast Lachancea thermotolerans is of significant biotechnological interest, and selected strains of this species have become commonly used starter cultures in wine fermentation. However, the impact of this species on wine is frequently limited by the rapid dominance of Saccharomyces cerevisiae strains which are better adapted to wine alcoholic fermentation conditions. Previous studies have shown that the major limiting factor for L. thermotolerans competitive performance in the wine ecosystem is oxygen availability, and not ethanol levels as had been previously suggested. Here we investigated the transcriptional response of L. thermotolerans to anaerobiosis in wine fermentation conditions. The data show that L. thermotolerans broadly redirects gene expression towards genes involved in central carbon metabolism, lipid metabolism, remodeling of the cell wall as well as autophagy. Furthermore, the induction of genes that are likely involved in the generation of lactate indicates a redirection of metabolic flux towards this metabolite. The data provide the first insight into the oxygen-dependent response of L. thermotolerans and suggest potential genetic targets to improve lactate production and/or anaerobic fermentation performance of this yeast.

Comparison of microbial diversity during two different wine fermentation processes

Wine production is a complex procedure in which an important role is played by many microorganisms, particularly yeasts and bacteria. In modern wineries, alcoholic fermentation is usually carried out by adding microbial starter cultures of Saccharomyces cerevisiae strains for precisely controlled production. Nowadays, in the Slovak Republic, autochthonous vinification is getting more popular. The present article deals with the comparison of two vinification approaches, namely spontaneous fermentation and fermentation controlled by a standard commercial S. cerevisiae starter, from the point of view of microbiota dynamics and the chemical characteristics of the wines produced. The dynamics of microbial populations were determined during the fermentation process by a 16S and 28S rRNA next-generation sequencing approach. A profile of the volatile compounds during these fermentation processes was identified by solid-phase microextraction (SPME) coupled to gas chromatography-mass spectrometry (GC-MS). In summary, the microbial diversity in the m1 phase (initial must) was higher, despite the presence of the starter culture. In the m3 phase (young wine), the microbiome profiles of both batches were very similar. It seems that the crucial phase in order to study the relationship of the microbiome and the resulting product should be based on the m2 phase (fermented must), where the differences between the autochthonous and inoculated batches were more evident.

The Effect of Non-Saccharomyces and Saccharomyces Non-Cerevisiae Yeasts on Ethanol and Glycerol Levels in Wine

Non-Saccharomyces and Saccharomyces non-cerevisiae studies have increased in recent years due to an interest in uninoculated fermentations, consumer preferences, wine technology, and the effect of climate change on the chemical composition of grapes, juice, and wine. The use of these yeasts to reduce alcohol levels in wines has garnered the attention of researchers and winemakers alike. This review critically analyses recent studies concerning the impact of non-Saccharomyces and Saccharomyces non-cerevisiae on two important parameters in wine: ethanol and glycerol. The influence they have in sequential, co-fermentations, and solo fermentations on ethanol and glycerol content is examined. This review highlights the need for further studies concerning inoculum rates, aeration techniques (amount and flow rate), and the length of time before Saccharomyces cerevisiae sequential inoculation occurs. Challenges include the application of such sequential inoculations in commercial wineries during harvest time.

Oenological potential of non-Saccharomyces yeasts to mitigate effects of climate change in winemaking: impact on aroma and sensory profiles of Treixadura wines

The effects of climate change on wine include high-alcohol content, low acidity and aroma imbalance. The potential of several non-Saccharomyces wine yeasts to mitigate these effects was evaluated by sequential fermentation of Treixadura grape must. Fermentations with only Saccharomyces cerevisiae ScXG3 and a spontaneous process were used as control assays. All yeast strains were obtained from the yeast collection of Estación de Viticultura e Enoloxía de Galicia (EVEGA), Galicia, Spain. Fermentation kinetics as well as yeast dynamics and implantation ability varied depending on inoculated yeasts. In addition, the results showed significant differences in the chemical composition of wine. Starmerella bacillaris 474 reduced the alcohol content (1.1% vol) and increased the total acidity (1.2 g L-1) and glycerol of wines. Fermentation with Lachancea thermotolerans Lt93 and Torulaspora delbrueckii Td315 also decreased the alcohol content, although to a lesser extent (0.3% and 0.7% vol, respectively); however, their effect on wine acidity was less significant. The wines also differed in their concentration of volatile compounds and sensory characteristics. Thus, wines made with Metschnikowia fructicola Mf278 and S. cerevisiae ScXG3 had higher content of esters, acetates and some acids than other wines, and were most appreciated by tasters due to their fruity character and overall impression.

Investigations of the mechanisms of interactions between four non-conventional species with Saccharomyces cerevisiae in oenological conditions

Fermentation by microorganisms is a key step in the production of traditional food products such as bread, cheese, beer and wine. In these fermentative ecosystems, microorganisms interact in various ways, namely competition, predation, commensalism and mutualism. Traditional wine fermentation is a complex microbial process performed by Saccharomyces and non-Saccharomyces (NS) yeast species. To better understand the different interactions occurring within wine fermentation, isolated yeast cultures were compared with mixed co-cultures of one reference strain of S. cerevisiae with one strain of four NS yeast species (Metschnikowia pulcherrima, M. fructicola, Hanseniaspora opuntiae and H. uvarum). In each case, we studied population dynamics, resource consumed and metabolites produced from central carbon metabolism. This phenotyping of competition kinetics allowed us to confirm the main mechanisms of interaction between strains of four NS species. S. cerevisiae competed with H. uvarum and H. opuntiae for resources although both Hanseniaspora species were characterized by a strong mortality either in mono or mixed fermentations. M. pulcherrima and M. fructicola displayed a negative interaction with the S. cerevisiae strain tested, with a decrease in viability in co-culture. Overall, this work highlights the importance of measuring specific cell populations in mixed cultures and their metabolite kinetics to understand yeast-yeast interactions. These results are a first step towards ecological engineering and the rational design of optimal multi-species starter consortia using modeling tools. In particular the originality of this paper is for the first times to highlight the joint-effect of different species population dynamics on glycerol production and also to discuss on the putative role of lipid uptake on the limitation of some non-conventional species growth although interaction processes.

Lower-alcohol wines produced by Metschnikowia pulcherrima and Saccharomyces cerevisiae co-fermentations: The effect of sequential inoculation timing

In Latin, 'pulcherrima' is a superlative form of an adjective that translates as beautiful. Apart from being 'the most beautiful' yeast, Metschnikowia pulcherrima has a remarkable potential in production of wines with lower ethanol content. The oenological performance of six M. pulcherrima strains was hereby tested in sequential cultures with Saccharomyces cerevisiae. The best-performing strain MP2 was further characterised in fermentations with different S. cerevisiae inoculation delays in both white grape juice and Chemically Defined Grape Juice Medium (CDGJM). The analysis of main metabolites, undertaken prior to sequential inoculations and upon fermentation completion, highlighted metabolic interactions and carbon sinks other than ethanol in MP2 treatments. Depending on the inoculation delay, MP2 white wines contained between 0.6% and 1.2% (v/v) less ethanol than the S. cerevisiae monoculture, with even larger decreases detected in the CDGJM. The MP2 treatments also contained higher concentrations of TCA cycle by-products (i.e. fumarate and succinate) and glycerol, and lower concentrations of acetic acid. The analysis of volatile compounds showed increased production of acetate esters and higher alcohols in all MP2 wines, alongside other compositional alterations arising from the S. cerevisiae inoculation delay.

Yeast-Yeast Interactions: Mechanisms, Methodologies and Impact on Composition

During the winemaking process, alcoholic fermentation is carried out by a consortium of yeasts in which interactions occurs. The consequences of these interactions on the wine matrix have been widely described for several years with the aim of controlling the winemaking process as well as possible. In this review, we highlight the wide diversity of methodologies used to study these interactions, and their underlying mechanisms and consequences on the final wine composition and characteristics. The wide variety of matrix parameters, yeast couples, and culture conditions have led to contradictions between the results of the different studies considered. More recent aspects of modifications in the composition of the matrix are addressed through different approaches that have not been synthesized recently. Non-volatile and volatile metabolomics, as well as sensory analysis approaches are developed in this paper. The description of the matrix composition modification does not appear sufficient to explain interaction mechanisms, making it vital to take an integrated approach to draw definite conclusions on them.

Fermentative and post-fermentative oxygenation of Corvina red wine: influence on phenolic and volatile composition, colour and wine oxidative response

BACKGROUND

During the production of red wine, moderate uptake of oxygen in the post-fermentative phase helps the stabilization of colour and the decrease of astringent tannins. However, the influence of oxygen uptake during the fermentative phase in must has not been completely investigated. In this study we evaluated the effect of controlled oxygen supply during fermentation-maceration of Corvina grapes on colour characteristics, tannins, volatile compounds, acetaldehyde production and oxidative stability of the finished wine.

RESULTS

Oxygen supply during fermentation improved the formations of stable pigments of Corvina wines due to the higher production of acetaldehyde. However, in wines treated with oxygen a lower production of fruity esters by yeasts was observed. Wines obtained from higher oxygen exposure during fermentation-maceration showed reduced ability to react with oxygen during storage.

CONCLUSIONS

Fermentative and post-fermentative oxygenation should be considered as a technological approach for modifying colour composition and stability, as well as oxidative behaviour of wine during aging. © 2020 Society of Chemical Industry.

Ecological interactions are a primary driver of population dynamics in wine yeast microbiota during fermentation

Spontaneous wine fermentation is characterized by yeast population evolution, modulated by complex physical and metabolic interactions amongst various species. The contribution of any given species to the final wine character and aroma will depend on its numerical persistence during the fermentation process. Studies have primarily evaluated the effect of physical and chemical factors such as osmotic pressure, pH, temperature and nutrient availability on mono- or mixed-cultures comprising 2-3 species, but information about how interspecies ecological interactions in the wine fermentation ecosystem contribute to population dynamics remains scant. Therefore, in the current study, the effect of temperature and sulphur dioxide (SO2) on the dynamics of a multi-species yeast consortium was evaluated in three different matrices including synthetic grape juice, Chenin blanc and Grechetto bianco. The population dynamics were affected by temperature and SO2, reflecting differences in stress resistance and habitat preferences of the different species and influencing the production of most volatile aroma compounds. Evidently at 15 °C and in the absence of SO2 non-Saccharomyces species were dominant, whereas at 25 °C and when 30 mg/L SO2 was added S. cerevisiae dominated. Population growth followed similar patterns in the three matrices independently of the conditions. The data show that fermentation stresses lead to an individual response of each species, but that this response is strongly influenced by the interactions between species within the ecosystem. Thus, our data suggest that ecological interactions, and not only physico-chemical conditions, are a dominant factor in determining the contribution of individual species to the outcome of the fermentation.

Volatile profile of reduced alcohol wines fermented with selected non-Saccharomyces yeasts under different aeration conditions

Over the last decades there has been an increase in ethanol concentration in wine. High ethanol concentration may impact negatively wine flavor and can be associated with harmful effects on human health. In this study, we investigated a microbiological approach to reduce wine ethanol concentration, using three non-Saccharomyces yeast strains (Metschnikowia pulcherrima, Torulaspora delbrueckii and Zygosaccharomyces bailii) in sequential fermentations with S. cerevisiae under different aeration conditions. At the same time, we evaluated the volatile profile of the resulting reduced alcohol Chardonnay wines. Results showed that the non-Saccharomyces yeasts tested were able to reduce wine ethanol concentration when oxygen was provided. Compared to S. cerevisiae wines, ethanol reduction was 1.6% v/v, 0.9% v/v and 1.0% v/v for M. pulcherrima, T. delbrueckii and Z. bailii sequential fermentations, respectively. Under the conditions evaluated here, aeration did not affect acetic acid production for any of the non-Saccharomyces strains tested. Although aeration affected wine volatile profiles, this was depended on yeast strain. Thus, wines produced with M. pulcherrima under aeration of 0.05 volume of air per volume of culture per minute (VVM) showed excessive ethyl acetate content, while Z. bailli wines produced with 0.05 VVM aeration had increased concentrations of higher alcohols and volatile acids. Increased concentrations of these compounds over their sensory thresholds, are likely to impact negatively on wine sensory profile. Contrarily, all three non-Saccharomyces strains under 0.025 VVM aeration conditions produced wines with reduced ethanol concentration and acceptable chemical volatile profiles.

Influence of cell-cell contact between L. thermotolerans and S. cerevisiae on yeast interactions and the exo-metabolome

Sequential fermentation of grape must inoculated with L. thermotolerans and then S. cerevisiae 24 h later (typical wine-making practice) was conducted with or without cell-cell contact between the two yeast species. We monitored cell viability of the two species throughout fermentation by flow cytometry. The cell viability of S. cerevisiae decreased under both conditions, but the decrease was greater if there was cell-cell contact. An investigation of the nature of the interactions showed competition between the two species for nitrogen compounds, oxygen, and must sterols. Volatile-compound analysis showed differences between sequential and pure fermentation and that cell-cell contact modifies yeast metabolism, as the volatile-compound profile was significantly different from that of sequential fermentation without cell-cell contact. We further confirmed that cell-cell contact modifies yeast metabolism by analyzing the exo-metabolome of all fermentations by FT-ICR-MS analysis. These analyses show specific metabolite production and quantitative metabolite changes associated with each fermentation condition. This study shows that cell-cell contact not only affects cell viability, as already reported, but markedly affects yeast metabolism.

Torulaspora delbrueckii produces high levels of C5 and C6 polyols during wine fermentations

Non-Saccharomyces yeasts impact wine fermentations and can diversify the flavor profiles of wines. However, little information is available on the metabolic networks of most of these species. Here we show that unlike the main wine yeast Saccharomyces cerevisiae, Torulaspora delbrueckii and to a lesser extent Lachancea thermotolerans produce significant concentrations of C5 and C6 polyols under wine fermentation conditions. In particular, D-arabitol, D-sorbitol and D-mannitol were produced at significant levels. Their release into the extracellular matrix started when that of glycerol ceased. The data also show that polyol production is influenced by initial sugar concentration, repressed by acetic acid and induced in ethanol supplemented media. Moreover, unlike glycerol and sorbitol, mannitol was partially re-assimilated when populations started to decline. The findings suggest that polyol synthesis is a physiological adaptation to stressful conditions characteristic of alcoholic fermentation and that these polyols may serve a similar purpose as glycerol production in S. cerevisiae, including osmoadaptation and redox balancing.

RNA-seq based transcriptional analysis of Saccharomyces cerevisiae and Lachancea thermotolerans in mixed-culture fermentations under anaerobic conditions

Background

In wine fermentation starter cultures, the blending of non-Saccharomyces yeast with Saccharomyces cerevisiae to improve the complexity of wine has become common practice, but data regarding the impact of co-cultivation on yeast physiology and on genetic and metabolic regulation remain limited. Here we describe a transcriptomic analysis of mixed fermentations of Saccharomyces cerevisiae and Lachancea thermotolerans. The fermentations were carried out in carefully controlled environmental conditions in a bioreactor to reduce transcriptomic responses that would be due to factors other than the presence of the second species.

Results

The transcriptomic data revealed that both yeast species showed a clear response to the presence of the other. Affected genes primarily belonged to two groups: genes whose expression can be linked to the competition for certain trace elements such as copper and iron, as well as genes required for cell wall structure and integrity. Furthermore, the data revealed divergent transcriptional responses with regard to carbon metabolism in response to anoxic conditions.

Conclusions

The results suggest that the mixed fermentation created a more competitive and stressful environment for the two species than single strain fermentations independently from total biomass, i.e. competition between cells of the same species is less stressful, or may present a different set of challenges, than interspecies competition. The changes in cell wall and adhesion properties encoding genes suggest that the adjustment of physical contact between cells may play a direct role in the response to the presence of competing species.

Electronic supplementary material

The online version of this article (10.1186/s12864-019-5511-x) contains supplementary material, which is available to authorized users.

Lachancea yeast species: Origin, biochemical characteristics and oenological significance

The genus Lachancea, first proposed in 2003, currently comprises 12 valid species, all found to have eight chromosomes. Lachancea spp. occupy a myriad of natural and anthropic habitats, and their geographic as well as ecological origin have been identified as key drivers in the genetic variations amongst strains of several of the species. Lachancea thermotolerans is the type species of the genus and also the most widely explored, especially for its role in fermentation environments. Indeed, L. thermotolerans is desired for its ability to acidify beer and wine through the production of lactic acid, and to enhance aroma and flavor through increased production of various compounds. Similarly, L. fermentati has been characterized for its potential contribution to the chemical composition of these beverages, albeit to a lesser extent, while other species have received little attention. Overall, members of the genus Lachancea form part of the microbiomes in many fermentation ecosystems and contribute directly or indirectly to the modulation of aroma and flavor of different products. The current review provides an overview of this genus, including the latest reports on the genetic and biochemical characteristics of member species, as well as their biotechnological potential.

Investigating the Effect of Selected Non-Saccharomyces Species on Wine Ecosystem Function and Major Volatiles

Natural alcoholic fermentation is initiated by a diverse population of several non-Saccharomyces yeast species. However, most of the species progressively die off, leaving only a few strongly fermentative species, mainly Saccharomyces cerevisiae. The relative performance of each yeast species is dependent on its fermentation capacity, initial cell density, ecological interactions as well as tolerance to environmental factors. However, the fundamental rules underlying the working of the wine ecosystem are not fully understood. Here we use variation in cell density as a tool to evaluate the impact of individual non-Saccharomyces wine yeast species on fermentation kinetics and population dynamics of a multi-species yeast consortium in synthetic grape juice fermentation. Furthermore, the impact of individual species on aromatic properties of wine was investigated, using Gas Chromatography-Flame Ionization Detector. Fermentation kinetics was affected by the inoculation treatment. The results show that some non-Saccharomyces species support or inhibit the growth of other non-Saccharomyces species in the multi-species consortium. Overall, the fermentation inoculated with a high cell density of Starmerella bacillaris displayed the fastest fermentation kinetics while fermentation inoculated with Hanseniaspora vineae showed the slowest kinetics. The production of major volatiles was strongly affected by the treatments, and the aromatic signature could in some cases be linked to specific non-Saccharomyces species. In particular, Wickerhamomyces anomalus at high cell density contributed to elevated levels of 2-Phenylethan-1-ol whereas Starm. bacillaris at high cell density resulted in the high production of 2-methylpropanoic acid and 3-Hydroxybutanone. The data revealed possible direct and indirect influences of individual non-Saccharomyces species within a complex consortium, on wine chemical composition.

Microbiological strategies to produce beer and wine with reduced ethanol concentration

Changes in consumer preferences, government policies and environmental conditions have driven research efforts towards producing alcoholic beverages with reduced alcohol content, namely wine and beer. While the strategies available to accomplish this goal vary for wine and beer, a common approach relies on the use of yeast strains which are less efficient at producing ethanol. Here we discuss current research on the isolation and/or generation of yeast strains able to produce beer or wine with reduced ethanol concentration. Particular consideration is given to the impact of 'low-ethanol' yeasts on volatile composition and sensory profile of beer and wine.

Non-Saccharomyces in Wine: Effect Upon Oenococcus oeni and Malolactic Fermentation

This work is a short review of the interactions between oenological yeasts and lactic acid bacteria (LAB), especially Oenococcus oeni, the main species carrying out the malolactic fermentation (MLF). The emphasis has been placed on non-Saccharomyces effects due to their recent increased interest in winemaking. Those interactions are variable, ranging from inhibitory, to neutral and stimulatory and are mediated by some known compounds, which will be discussed. One phenomena responsible of inhibitory interactions is the media exhaustion by yeasts, and particularly a decrease in L-malic acid by some non-Saccharomyces. Clearly ethanol is the main inhibitory compound of LAB produced by S. cerevisiae, but non-Saccharomyces can be used to decrease it. Sulfur dioxide and medium chain fatty acids (MCFAs) produced by yeasts can exhibit inhibitory effect upon LAB or even result lethal. Interestingly mixed fermentations with non-Saccharomyces present less MCFA concentration. Among organic acids derived as result of yeast metabolism, succinic acid seems to be the most related with MLF inhibition. Several protein factors produced by S. cerevisiae inhibiting O. oeni have been described, but they have not been studied in non-Saccharomyces. According to the stimulatory effects, the use of non-Saccharomyces can increase the concentration of favorable mediators such as citric acid, pyruvic acid, or other compounds derived of yeast autolysis such as peptides, glucans, or mannoproteins. The emergence of non-Saccharomyces in winemaking present a new scenario in which MLF has to take place. For this reason, new tools and approaches should be explored to better understand this new winemaking context.

Inoculation of Torulaspora delbrueckii as a bio-protection agent in winemaking

In oenology, bio-protection consists in adding bacteria, yeasts or a mixture of microorganisms on grape must before fermentation in order to reduce the use of chemical compounds such as sulphites. More particularly, non-Saccharomyces yeasts are used as a total or partial alternative to sulphites. However, scientific data capable of proving the effectiveness of adding these yeasts on grape must is lacking. This study reports the analysis of antimicrobial and antioxidant effects of one non-Saccharomyces yeast, Torulaspora delbrueckii, inoculated at the beginning of the white winemaking process in two Burgundian wineries as an alternative to sulphiting. The implantation of the T. delbrueckii strain was successful in both wineries and had no impact on fermentation kinetics. Adding T. delbrueckii reduced biodiversity during the pre-fermentation stages compared to sulphited controls and it also effectively limited the development of spoilage microorganisms in the same way as the addition of sulphites. T. delbrueckii could protect must and wine from oxidation as demonstrated by the analysis of colour and phenolic compounds. This is the first evidence that early addition of T. delbrueckii during winemaking can be a microbiogical and chemical alternative to sulphites. However, its contribution seems to be matrix dependent.

The Use of Mixed Populations of Saccharomyces cerevisiae and S. kudriavzevii to Reduce Ethanol Content in Wine: Limited Aeration, Inoculum Proportions, and Sequential Inoculation

Saccharomyces cerevisiae is the most widespread microorganism responsible for wine alcoholic fermentation. Nevertheless, the wine industry is currently facing new challenges, some of them associate with climate change, which have a negative effect on ethanol content and wine quality. Numerous and varied strategies have been carried out to overcome these concerns. From a biotechnological point of view, the use of alternative non-Saccharomyces yeasts, yielding lower ethanol concentrations and sometimes giving rise to new and interesting aroma, is one of the trendiest approaches. However, S. cerevisiae usually outcompetes other Saccharomyces species due to its better adaptation to the fermentative environment. For this reason, we studied for the first time the use of a Saccharomyces kudriavzevii strain, CR85, for co-inoculations at increasing proportions and sequential inoculations, as well as the effect of aeration, to improve its fermentation performance in order to obtain wines with an ethanol yield reduction. An enhanced competitive performance of S. kudriavzevii CR85 was observed when it represented 90% of the cells present in the inoculum. Furthermore, airflow supply of 20 VVH to the fermentation synergistically improved CR85 endurance and, interestingly, a significant ethanol concentration reduction was achieved.

The Impact of Saccharomyces cerevisiae on a Wine Yeast Consortium in Natural and Inoculated Fermentations

Natural, also referred to as spontaneous wine fermentations, are carried out by the native microbiota of the grape juice, without inoculation of selected, industrially produced yeast or bacterial strains. Such fermentations are commonly initiated by non-Saccharomyces yeast species that numerically dominate the must. Community composition and numerical dominance of species vary significantly between individual musts, but Saccharomyces cerevisiae will in most cases dominate the late stages of the fermentation and complete the process. Nevertheless, non-Saccharomyces species contribute significantly, positively or negatively, to the character and quality of the final product. The contribution is species and strain dependent and will depend on each species or strain's absolute and relative contribution to total metabolically active biomass, and will therefore, be a function of its relative fitness within the microbial ecosystem. However, the population dynamics of multispecies fermentations are not well understood. Consequently, the oenological potential of the microbiome in any given grape must, can currently not be evaluated or predicted. To better characterize the rules that govern the complex wine microbial ecosystem, a model yeast consortium comprising eight species commonly encountered in South African grape musts and an ARISA based method to monitor their dynamics were developed and validated. The dynamics of these species were evaluated in synthetic must in the presence or absence of S. cerevisiae using direct viable counts and ARISA. The data show that S. cerevisiae specifically suppresses certain species while appearing to favor the persistence of other species. Growth dynamics in Chenin blanc grape must fermentation was monitored only through viable counts. The interactions observed in the synthetic must, were upheld in the natural must fermentations, suggesting the broad applicability of the observed ecosystem dynamics. Importantly, the presence of indigenous yeast populations did not appear to affect the broad interaction patterns between the consortium species. The data show that the wine ecosystem is characterized by both mutually supportive and inhibitory species. The current study presents a first step in the development of a model to predict the oenological potential of any given wine mycobiome.