Yeasts for low input winemaking: Microbial terroir and flavor differentiation

Occurrence and Persistence of Saccharomyces cerevisiae Population in Spontaneous Fermentation and the Relation with "Winery Effect"

The yeast Saccharomyces cerevisiae ensures successful fermentation in winemaking, although the persistent use of commercial strains lead to the loss of aroma complexity of wines. Hence, the research of indigenous S. cerevisiae with proper oenological features and well adapted to specific wine-growing areas become of great interest for winemakers. Here, 206 pure cultures of S. cerevisiae were isolated from two wineries during a two-year sampling campaign and bio-typed through interdelta sequences analyses with the aim to evaluate the occurrence and persistence of the S. cerevisiae wild population linked to each winery. Both wineries belong to the same Verdicchio DOC wine area (Castelli di Jesi), and never used commercial yeasts during fermentation. Results showed 19 different biotypes with a specific population of S. cerevisiae in each winery, without cross-contamination with each other and with commercial starter strains. Moreover, inside each winery a persistence of some dominant biotypes was observed over time (three biotypes in winery 1; 95% of isolates in the two years and one biotype in winery 2; 20% of isolates in the two years), indicating a sort of "winery-effect". The evaluation of S. cerevisiae populations for the oenological characters by microfermentations showed a proper and well distinct aromatic imprinting on the resulted wines supporting the concept of "winery effect".

Impact of phenylalanine on Hanseniaspora vineae aroma metabolism during wine fermentation

Hanseniaspora vineae exhibits extraordinary positive oenological characteristics contributing to the aroma and texture of wines, especially by its ability to produce great concentrations of benzenoid and phenylpropanoid compounds compared with conventional Saccharomyces yeasts. Consequently, in practice, sequential inoculation of H. vineae and Saccharomyces cerevisiae allows to improve the aromatic quality of wines. In this work, we evaluated the impact on wine aroma produced by increasing the concentration of phenylalanine, the main amino acid precursor of phenylpropanoids and benzenoids. Fermentations were carried out using a Chardonnay grape juice containing 150 mg N/L yeast assimilable nitrogen. Fermentations were performed adding 60 mg/L of phenylalanine without any supplementary addition to the juice. Musts were inoculated sequentially using three different H. vineae strains isolated from Uruguayan vineyards and, after 96 h, S. cerevisiae was inoculated to complete the process. At the end of the fermentation, wine aromas were analysed by both gas chromatography-mass spectrometry and sensory evaluation through a panel of experts. Aromas derived from aromatic amino acids were differentially produced depending on the treatments. Sensory analysis revealed more floral character and greater aromatic complexity when compared with control fermentations without phenylalanine added. Moreover, fermentations performed in synthetic must with pure H. vineae revealed that even tyrosine can be used in absence of phenylalanine, and phenylalanine is not used by this yeast for the synthesis of tyrosine derivatives.

Biodiversity and brewing attitude of non-Saccharomyces strains isolated from Uruguayan vineyards and other ecosystems

In recent years, interest in non-Saccharomyces yeasts for the innovation and development of different and alternative beer styles has been increasing, especially for the microbrewing industry. This work studied the biodiversity of non-Saccharomyces yeasts based on isolates from grapes of different Uruguayan vineyards, craft breweries and raw materials, with the aim of selecting autochthonous non-Saccharomyces yeasts with a brewing attitude. Brewing tests were performed on synthetic wort developed for this purpose, and the evolution of alcoholic fermentation was monitored by measuring glucose, maltose, maltotriose consumption, ethanol and glycerol production and final sensory analysis. A total of two hundred seventy-one yeast strains belonging to different genera were evaluated according to these parameters. After evaluating alcoholic fermentation performance, a native yeast strain belonging to the species Starmerella meliponinorum was selected due to its high maltotriose consumption and glycerol production, making it a very promising brewing yeast, especially for production of low carbohydrate beers.

Wine aroma modification by Hanseniaspora uvarum: A multiple-step strategy for screening potential mixed starters

Hanseniaspora uvarum is a prevalent yeast species in vineyards. However, its application in grape wine fermentation remains limited. This study used culture-dependent and -independent approaches to investigate the dynamics of H. uvarum during the spontaneous fermentation of Cabernet Sauvignon grapes. The results revealed that H. uvarum constituted 77.49 % of the non-Saccharomyces yeast population during fermentation. An indigenous strain, QTX-C10, was isolated from the 148 H. uvarum strains using a multistep screening strategy. The 1:1 co-inoculation of QTX-C10 with Saccharomyces cerevisiae proved to be an optimal strategy for mixed fermentation, resulting in a 48.54 %-59.55 % increase in ethyl esters in Cabernet Sauvignon wine and a 96.94 %-110.92 % increase in Chardonnay wine. Furthermore, this approach reduced the acetic acid levels by 12.50 %-17.07 % for Cabernet Sauvignon wine and 10.81 %-17.78 % for Chardonnay wine. Additionally, increased ethyl ester content may enhance the tropical fruit flavor of Cabernet Sauvignon wines.

Exploring the ecological characteristics of natural microbial communities along the continuum from grape berries to winemaking

Under natural conditions, a complex and dynamic microbial ecosystem exists on the grape epidermis, which plays an important role in safeguarding grape health and facilitating the conversion of grapes into wine. However, current viticulture and vinification are flooded with excessive chemical additives and commercial ferments, leading to a reduction in microbial diversity, affecting the ecological balance of the natural microbiota and masking the wine terroir. This experiment comprehensively explored the continuous changes in the natural microbiota from the Ecolly (Vitis vinifera L.) grape epidermis to spontaneous fermentation over two years. The results suggested that microbial community structure and composition were significantly influenced by vintage and growing stage, with fungal genera being more stable than bacterial genera during the growing season. The fungal genera Alternaria, Ascochyta, Gibberella and Dissoconium and the bacterial genera Pantoea, Sediminibacterium, Ralstonia and Sphingomonas were mainly present on the grape epidermis in both years. The natural microbial diversity decreased from grape growth to spontaneous fermentation, and the fermentation environment reshapes the community structure, composition and diversity of the wine microbial consortium. These findings provide insights to promote cultivation and fermentation management strategies, advocate natural terroir attributes for grapes and wines, and promote sustainable development of the wine industry.

Vitis vinifera Manseng noir, the sister of Tannat. Alternative variety for low alcohol wines produced in Uruguayan conditions

Vitis vinifera Tannat was introduced in Uruguay in 1870 from the Basque Pyrenees, and within several grapevines it became the variety best adapted to our viticultural conditions. Recently, through genetic analysis it was demonstrated that Manseng Noir, in addition to originate from the same region of Tannat, is the only natural sister identified within 2500 Vitis varieties surveyed [1]. Given the small commercial vineyard of this variety in France, after several years we have managed to plant in 2019 the first vineyard outside the Pyrenees in Uruguay. In 2021 and 2022 harvests, its elaboration is achieved with the aim of comparing its wine with Tannat. Results obtained show that its agronomic phenotype, as well as aspects of sanity, acidity, and color intensity are similar to Tannat, but with the particularity that grapes are of moderate ripening, 12.5% of alc., total polyphenol index was 12% lower than the control Tannat at 14% of alcohol. Interestingly, Manseng Noir shows an early smoothness in its tannins that allow to achieve lower alcohol wines, still powerful color and structure but less astringency in the mouth. Its complete genome was sequenced by Illumina technology and comparative genome analysis with Tannat was carried on. Genetic, metabolomic and sensory analyzes comparison with Tannat are discussed in this work.

Proteolytic activity under white wine fermentation by Hanseniaspora vineae yeast strains

Apiculate yeasts from Hanseniaspora genus are predominant on the native flora of grapevines, while Hanseniaspora uvarum is well known for its abundant presence in grapes, it results generally, in detrimental quality effects on wine due to high production of acetic acid. By contrast, Hanseniaspora vineae is better adapted to fermentation, increasing flavor complexity in wines as it has been demonstrated in winemaking practices during the last decade. We obtained a collection of more than 22 different Hanseniaspora vineae strains from which we could detect, by a plating screening method, high and moderate protease activity. In this study, we tested these strains under real winemaking conditions on a Sauvignon blanc white wine must. Results obtained demonstrated that there is an interesting protease active diversity in all H. vineae strains when compared to conventional fermentations conducted by Saccharomyces cerevisiae. Four H. vineae strains showed a decrease in wine protein turbidity, up to three times lower than that observed in S. cerevisiae, which imply a significant decrease in the demand for bentonite before bottling. This attribute of some H. vineaestrains should be very attractive at the commercial level to reduce manipulations and flavor removal in the production of delicate white wines such as Sauvignon blanc.

Forests influence yeast populations vectored by insects into vineyards

Introduction

In the vineyard, yeast communities impact the ripening and fermentation of grapes and are influenced by geographical location, climate, and soil characteristics. Despite the great advancement in our knowledge of the vineyard mycobiota, a key step of the process leading to the definition of the vineyard yeast community is still poorly understood: if geography, climate, and soil influence the mycobiota, potentially through selection, where do the yeast originate from, and how can they reach the vineyard? In this perspective, it is currently acknowledged that forests host several yeast species and that insects, particularly social wasps, can vector and maintain the yeasts known to populate the vineyard. Alas, the conveyance, fostered by insects, of yeasts from the forest to the vineyard has not been proven yet. In this study, we aimed to assess the existence of links between a potential natural source of yeasts (woods), the vectors (social wasps), and the composition of the vineyard mycobiota.

Methods

For this purpose, the mycobiota of wasps caught in six Italian vineyards were analyzed over 2 years through culturomics approaches.

Results

The results clearly indicate that the presence of wooded areas close to vineyards is associated with particular features of the mycobiota vectored by social wasps. Wasps caught in vineyards near wooded areas bear a higher number of yeast cells and higher biodiversity than insects caught in vineyards far from woods. Furthermore, insects caught in vineyards close to woods bear distinctive yeast populations, encompassing species such as Saccharomyces cerevisiae.

Discussion

Overall, our work provides fundamental insights into the ecology of the vineyard mycobiota and highlights the need to maintain a vineyard-woodland mosaic landscape, thus preserving the suitable habitat for yeast species relevant to wine-making.

Rumen Fermentation and Microbiome Responses to Enzymatic Hydrolysate of Cottonseed Protein Supplementation in Continuous In Vitro Culture

This study aimed to evaluate the effect of enzymatic hydrolysate of cottonseed protein (ECP) on the kinetic of gas production, rumen fermentation characteristics, and microbial diversity in continuous in vitro culture with a single factorial design of supplementation with various concentrations of ECP or yeast culture. Treatments were control (without supplementation, CON), supplementation with 10 g/kg Diamond-V XP yeast culture of substrate (XP), and supplementation with 6, 12 and 18 g/kg ECP of substrate (ECP1, ECP2, ECP3), each incubated with 30 mL of buffered incubation fluids and 200 mg of fermentation substrate in graduated glass syringes fitted with plungers for 48 h. Compared with the CON treatment, supplementation of XP yeast culture increased the cumulative gas production at 12 and 24 h, the concentration of ammonia nitrogen (NH3-N) concentration at 24 and 36 h, the concentration of microbial protein (MCP) concentration at 24 and 48 h, the molar butyrate proportion at 12, 24, and 48 h, the molar valerate proportion at 48 h, and the ratio of non-glucogenic to glucogenic acids (p < 0.05). Compared with the CON treatment, the concentration of MCP and the molar propionate proportion at 12 h were higher in the ECP1 treatment (p < 0.05); the cumulative gas production at 2, 4, and 12 h, the concentration of NH3-N at 36 h and the molar valerate proportion at 48 h were higher in the ECP2 treatment (p < 0.05); the cumulative gas production at 2, 12, and 48 h, the concentration of NH3-N at 12 and 36 h, the concentration of MCP at 12, 36, and 48 h, the molar butyrate proportion at 12 and 48 h, and the molar valerate proportion at 48 h were higher in the ECP3 treatment (p < 0.05). Compared with the CON treatment, supplementation with XP yeast culture significantly altered the relative abundance of the phyla Firmicutes, Kiritimatiellaeota, and Proteobacteria, while supplementation with ECP had minimal effect on bacterial diversity. The prediction of bacterial functions showed that the main gene functions of rumen bacteria are associated with carbohydrate metabolism, amino acid metabolism, and membrane transport. The findings of this study suggest that ECP can be used as a superior feed ingredient for ruminants, the suitable level of ECP was 18 g/kg in vitro experiment.

Natural and sustainable wine: a review

With the awakening of consumers' awareness of sustainable development issues and demand for terroir wines, natural wines provide opportunities for the future development of the wine industry. Microbiomes are integral to viticulture and winemaking, where various microorganisms can exert positive and negative effects on grape health and wine quality. Communities of microorganisms associated with the vineyard play an important role in soil productivity as well as disease resistance developed by the vine. Wine is a fermented natural product, and the vineyard serves as a key point of entry for quality-modulating microbiota, particularly in wine fermentations that are conducted without the addition of exogenous yeasts. Thus, the sources and persistence of wine-relevant microbiota in vineyards critically impact its quality. In this review, we first examined that mimicking natural ecological cultivation to improve microbial diversity can enhance vineyard ecological services and reduce external inputs; then we examined that grape berries naturally possess all the elements of winemaking, including the nutrients for microbial growth, driving forces for the microbiota succession, and the enzymatic system for biochemical reactions; finally, we examined food safety, stability, specific interventions, and sustainability of natural wine industry-scale practices.

Influence of Kazachstania spp. on the chemical and sensory profile of red wines

We report the fermentative traits of two Kazachstania species (K. aerobia and K. servazzii) in non-sterile red wine and the resulting chemical and sensory properties. This builds on our previous work which revealed that Kazachstania spp. increased acetate esters in sterilised white wine. In this study Kazachstania spp. were initially evaluated in laboratory-scale fermentations (500 mL) in Merlot must to assess whether similar increases in chemical/volatile compounds would occur. The impact of malolactic fermentation (MLF) by Oenococcus oeni (VP41) on aroma composition was considered and found to reduce ester profiles in Merlot wines. The sensory implications of sequential inoculation with Kazachstania spp., followed by Saccharomyces cerevisiae, were then evaluated in small-lot fermentations (7 kg) of Shiraz must. Fungal diversity was monitored during early fermentation stages and was influenced by the early implantation of Kazachstania spp., followed by the dominance of S. cerevisiae. The effect of MLF in Shiraz wines was inconclusive due to high ethanol levels providing an inhospitable environment for lactic acid bacteria. When compared to S. cerevisiae alone, Kazachstania spp. significantly increased acetate esters, particularly phenylethyl acetate and isoamyl acetate, in both Merlot and Shiraz. The Shiraz wines fermented with Kazachstania spp. had higher jammy and red fruit aroma/flavour compared to S. cerevisiae (monoculture) wines. No influence was observed on colour one-year post-bottling. Results from this study show the contribution of Kazachstania spp. to the aroma profile of red wines and demonstrate their potential as starter cultures for improving the aromatic complexity of wines.

Hanseniaspora vineae and the Concept of Friendly Yeasts to Increase Autochthonous Wine Flavor Diversity

In this perspective, we will explain the concept of “friendly” yeasts for developing wine starters that do not suppress desirable native microbial flora at the initial steps of fermentation, as what usually happens with Saccharomyces strains. Some non-Saccharomyces strains might allow the development of yeast consortia with the native terroir microflora of grapes and its region. The positive contribution of non-Saccharomyces yeasts was underestimated for decades. Avoiding them as spoilage strains and off-flavor producers was the main objective in winemaking. It is understandable, as in our experience after more than 30 years of wine yeast selection, it was shown that no more than 10% of the isolated native strains were positive contributors of superior flavors. Some species that systematically gave desirable flavors during these screening processes were Hanseniaspora vineae and Metschnikowia fructicola. In contrast to the latter, H. vineae is an active fermentative species, and this fact helped to build an improved juice ecosystem, avoiding contaminations of aerobic bacteria and yeasts. Furthermore, this species has a complementary secondary metabolism with S. cerevisiae, increasing flavor complexity with benzenoid and phenylpropanoid synthetic pathways practically inexistent in conventional yeast starters. How does H. vineae share the fermentation niche with other yeast strains? It might be due to the friendly conditions it creates, such as ideal low temperatures and low nitrogen demand during fermentation, reduced synthesis of medium-chain fatty acids, and a rich acetylation capacity of aromatic higher alcohols, well-known inhibitors of many yeasts. We will discuss here how inoculation of H. vineae strains can give the winemaker an opportunity to develop ideal conditions for flavor expression of the microbial terroir without the risk of undesirable strains that can result from spontaneous yeast fermentations.

Biocompatibility in Ternary Fermentations With Lachancea thermotolerans, Other Non-Saccharomyces and Saccharomyces cerevisiae to Control pH and Improve the Sensory Profile of Wines From Warm Areas

Global warming is causing serious problems, especially, in warm regions, where musts with excess sugars and high pH produce wines with decreased freshness and unstable evolution. This study aimed to determine biocompatibility between yeast species, the capacity for microbiological acidification, and the aromatic profile produced in ternary fermentations in which Lachancea thermotolerans has been co-inoculated with Hanseniaspora vineae, Torulaspora delbrueckii, or Metschnikowia pulcherrima, and the fermentation process is subsequently completed with sequential inoculation of Saccharomyces cerevisiae. For this purpose, different cell culture media and instruments were used such as infrared spectroscopy, enzymatic autoanalyzer, chromatograph coupled with a flame ionization detector, spectrophotometric analysis, among others. The behavior of these yeasts was evaluated alone and in co-inoculation, always finishing the fermentation with sequential inoculation of S. cerevisiae, at a stable temperature of 16°C and with a low level of sulfites (25 mg/L) in white must. Significant results were obtained in terms of biocompatibility using population counts (CFU/ml) in differential plating media that permitted monitoring. Quantification of the five species was studied. Concerning acidification by L. thermotolerans in co-inoculations, we showed some metabolic interactions, such as the inhibition of acidification when H. vineae/L. thermotolerans were used, generating just over 0.13 g/L of lactic acid and, conversely, a synergistic effect when M. pulcherrima/L. thermotolerans were used, achieving 3.2 g/L of lactic acid and a reduction in pH of up to 0.33. A diminution in alcohol content higher than 0.6% v/v was observed in co-inoculation with the L. thermotolerans/M. pulcherrima yeasts, with total sugar consumption and very slow completion of fermentation in the inoculations with H. vineae and T. delbrueckii. The aromatic composition of the wines obtained was analyzed and a sensory evaluation conducted, and it was found that both L. thermotolerans and co-inoculations retained more aromatic esters over time and had a lower evolution toward the yellow tones typical of oxidation and that the best sensory evaluation was that of the Lt + Mp co-inoculation. Lachancea thermotolerans and co-inoculations produced wines with low levels of volatile acidity (<0.4 g/L). This work shows that good consortia strategies with binary and ternary fermentations of yeast strains can be a powerful bio-tool for producing more complex wines.

Characterization of Microbial Dynamics and Volatile Metabolome Changes During Fermentation of Chambourcin Hybrid Grapes From Two Pennsylvania Regions

Microbial diversity present on grapes in wineries, and throughout fermentation has been associated with important metabolites for final wine quality. Although microbiome-metabolome associations have been well characterized and could be used as indicators of wine quality, the impact of regionality on the microbiome and metabolome is not well known. Additionally, studies between microbiome and metabolome have been conducted on single species grape such as Vitis vinifera instead of other species and interspecific hybrids. Although the Pennsylvania wine industry is relatively young compared to California, the industry has been experiencing rapid growth over the past decade and is expected to continue to grow in the future. Pennsylvania's climate of cold winters and high levels of rainfall throughout the growing season favors cultivation of interspecific hybrid grapes such as Vitis ssp. Chambourcin, one of the most commonly grown hybrid varieties in the state. Chambourcin is a prime candidate for studying the impact of regionality on microbiome-metabolome interactions as interspecific hybrid varieties could shape the future of winemaking. Here, we identify for the first time the regional distribution of microbial communities and their interactions with volatile metabolome during fermentation (0-20 days) by integrating high throughput Illumina sequencing (16S and ITS) and headspace-solid phase microextraction-gas chromatography-mass spectrometry. Analyzing 88 samples from nine wineries in the Central and East Pennsylvania regions, we observed high microbial diversity during early stages of fermentation (1-4 days) where non-Saccharomyces yeasts such as Starmerella and Aureobasidium and non-Oenococcus bacteria, Sphingomonas, likely contribute to microbial terroir to the resulting wines. Furthermore, key differentiators between two regions in Pennsylvania, as identified by LEfSe analysis, include the fungal genera Cladosporium and Kazachstania and the bacterial genera Lactococcus and Microbacterium. Moreover, 29 volatile fermentation metabolites were discriminated significantly (variable importance in projection > 1) between the two regions as shown by Partial Least Squares-Discriminant Analysis. Finally, Spearman's correlation identified regional differences of microbial-metabolite associations throughout fermentation that could be used for targeted microbiome manipulation to improve wine quality and preserve regionality. In summary, these results demonstrate the microbial signatures during fermentation and differential microorganisms and metabolites further support impact of regionality on Chambourcin wines in Pennsylvania.

Phenotypic and transcriptional analysis of Saccharomyces cerevisiae during wine fermentation in response to nitrogen nutrition and co-inoculation with Torulaspora delbrueckii

Nitrogen content of grape musts strongly impacts on fermentation performance and wine metabolite production. As nitrogen is a limiting nutrient in most grape musts, nitrogen supplementation is a common practice that ensures yeast growth during fermentation. However, preferred nitrogen sources -as ammonium- repress the genes related to alternative nitrogen sources consumption, usually involved in aromatic compounds production. Here, we describe the effect of high ammonium doses in Saccharomyces cerevisiae fermentation performance and wine properties, and how it is affected by yeast co-inoculation in mixed (S. cerevisiae + Torulaspora delbrueckii) fermentations. In addition, an RNA-seq analysis allowed us to study the S. cerevisiae transcriptional response to ammonium nutrition and yeast interaction, demonstrating that T. delbrueckii presence affects the global S. cerevisiae transcriptional response, reducing ammonium effects at both phenotypic -fermentation kinetics and metabolite production- and transcriptional levels, under experimental conditions.