The impact of fungicide treatments on yeast biota of Verdicchio and Montepulciano grape varieties

Culturable yeast community associated with grape must and honey bees sampled from apiaries located in the vineyards

AIM

In this study, we investigated culturable yeast community, present in grape must sampled from vineyards with apiaries on the borders, and in honey bees collected in these apiaries.

METHODS AND RESULTS

To this aim, yeasts isolated from spontaneously fermented grapes randomly collected in two vineyards (P1 and P2) with apiaries on the borders (A1 and A2) were compared to those isolated from spontaneously fermented grapes collected from a vineyard without apiary (P4). At the same time, yeast community was analyzed on bees collected in each apiary placed in the vineyards, in comparison to yeasts isolated from an apiary (A3) located far from the vineyards. The analysis was performed for two consecutive years (2021 and 2022). The isolated yeasts were identified by restriction analysis of amplified ITS region, followed by sequencing of ITS fragment.Our research showed that the presence of apiaries seems to increase yeast counts of grape must, in particular of Saccharomyces cerevisiae; furthermore, the permanence of apiaries in the vineyards allowed the recovering of these yeasts also from bees.

CONCLUSIONS

Our findings seem to corroborate the role of bees as vectors and reservoirs of oenologically relevant yeasts, such as a source of non-conventional yeasts with potential biotechnological applications.

Yeast communities of a North American hybrid wine grape differ between organic and conventional vineyards

AIMS

To compare the species diversity and composition of indigenous yeast communities of hybrid grapes from conventionally and organically cultivated vineyards of an emerging cool-climate wine producing region.

METHODS AND RESULTS

Illumina MiSeq sequences from L'Acadie blanc grape musts were processed and filtered to characterize indigenous yeast communities in organic and conventional vineyards of the Annapolis Valley wine region in Nova Scotia, Canada. While cultivation practice was not associated with yeast diversity or species richness, there was a strong effect on yeast community composition, with conventional vineyards characterized by higher proportions of Sporidiobolales and Filobasidium magnum, and organic vineyards supporting Filobasidium species other than F. magnum and higher proportions of Symmetrospora. There was also variation in yeast community composition among individual vineyards, and from year to year.

CONCLUSIONS

This is the first comprehensive assessment of yeasts associated with hybrid grapes grown using different cultivation practices in a North American cool climate wine region. Communities were dominated by basidiomycete yeasts and species composition of these yeasts differed significantly between vineyards employing organic and conventional cultivation practices. The role of basidiomycete yeasts in winemaking is not well understood, but some species may influence wine characteristics.

Yeast communities related to honeybees: occurrence and distribution in flowers, gut mycobiota, and bee products

Honeybee (Apis mellifera) is an important agricultural pollinator and a model for sociality. In this study, a deep knowledge on yeast community characterizing the honeybees' environmental was carried out. For this, a total of 93 samples were collected: flowers as food sources, bee gut mycobiota, and bee products (bee pollen, bee bread, propolis), and processed using culture-dependent techniques and a molecular approach for identification. The occurrence of yeast populations was quantitatively similar among flowers, bee gut mycobiota, and bee products. Overall, 27 genera and 51 species were identified. Basidiomycetes genera were predominant in the flowers while the yeast genera detected in all environments were Aureobasidium, Filobasidium, Meyerozyma, and Metschnikowia. Fermenting species belonging to the genera Debaryomyces, Saccharomyces, Starmerella, Pichia, and Lachancea occurred mainly in the gut, while most of the identified species of bee products were not found in the gut mycobiota. Five yeast species, Meyerozyma guilliermondii, Debaryomyces hansenii, Hanseniaspora uvarum, Hanseniaspora guilliermondii, and Starmerella roseus, were present in both summer and winter, thus indicating them as stable components of bee mycobiota. These findings can help understand the yeast community as a component of the bee gut microbiota and its relationship with related environments, since mycobiota characterization was still less unexplored. In addition, the gut microbiota, affecting the nutrition, endocrine signaling, immune function, and pathogen resistance of honeybees, represents a useful tool for its health evaluation and could be a possible source of functional yeasts. KEY POINTS: • The stable yeast populations are represented by M. guilliermondii, D. hansenii, H. uvarum, H. guilliermondii, and S. roseus. • A. pullulans was the most abondance yeast detective in the flowers and honeybee guts. • Aureobasidium, Meyerozyma, Pichia, and Hanseniaspora are the main genera resident in gut tract.

Ecological Distribution and Oenological Characterization of Native Saccharomyces cerevisiae in an Organic Winery

The relation between regional yeast biota and the organoleptic characteristics of wines has attracted growing attention among winemakers. In this work, the dynamics of a native Saccharomyces cerevisiae population was investigated in an organic winery. In this regard, the occurrence and the persistence of native S. cerevisiae were evaluated in the vineyard and winery and during spontaneous fermentation of two nonconsecutive vintages. From a total of 98 strains, nine different S. cerevisiae biotypes were identified that were distributed through the whole winemaking process, and five of them persisted in both vintages. The results of the oenological characterization of the dominant biotypes (I and II) show a fermentation behavior comparable to that exhibited by three common commercial starter strains, exhibiting specific aromatic profiles. Biotype I was characterized by some fruity aroma compounds, such as isoamyl acetate and ethyl octanoate, while biotype II was differentiated by ethyl hexanoate, nerol, and β-damascenone production also in relation to the fermentation temperature. These results indicate that the specificity of these resident strains should be used as starter cultures to obtain wines with distinctive aromatic profiles.

Use of Microwave Maceration in Red Winemaking: Effect on Fermentation and Chemical Composition of Red Wines

The objective of this study was to evaluate the effect of microwave treatment of crushed grapes on the yeast population of the must and on the development of alcoholic fermentation, as well as on the extraction of different compounds from the grapes such as polysaccharides and amino acids that can affect the organoleptic quality and stability of the wine. This study demonstrated for the first time the effect of the microwave treatment of grapes on native yeast species and their diversity, producing an increase in fermentation kinetics and a decrease in the lag phase. The microwave treatment produced a positive effect on the extraction of amino acids and polysaccharides from the grapes, resulting in significantly higher amounts of the main amino acids of the must and some major volatile compounds in the treated samples. The polysaccharides most affected by the microwave treatment were the PRAGs, the main polysaccharides liberated from grapes during the maceration.

Year, Location, and Variety Impact on Grape-Associated Mycobiota of Arkansas-Grown Wine Grapes for Wine Production

Wine grape berries (Vitis spp.) harbor a wide variety of yeasts and filamentous fungi that impact grapevine health and the winemaking process. Identification of these fungi could be important for controlling and improving wine production. The use of high-throughput sequencing (HTS) strategies has enabled identification and quantification of bacterial and fungal species in vineyards. The aims of this study were to identify mycobiota from Cabernet Sauvignon and Zinfandel (V. vinifera), Carlos and Noble muscadines (V. rotundifolia), Cynthiana (V. aestivalis), and Vignoles hybrid (cross of different Vitis spp.) grapes, and investigate the effect of grape variety, location, and year on grape fungal communities. Grape berries were collected in 2016 and 2017 from four vineyards located in Arkansas. The HTS of the Internal Transcribed Spacer 1 region was used to identify grape indigenous epiphytic and endophytic fungal communities. The predominant genera identified on the Arkansas wine grapes were Uwebraunia, Zymoseptoria, Papiliotrema, Meyerozyma, Filobasidium, and Curvibasidium. Overall, the data suggested that grape fungal community distribution and relative abundance were influenced by grape variety, year, and location, but each was influenced to a different extent. Not only were grape mycobiota influenced by year, variety, and location but also it appeared that communities from the previous year impacted microbial communities the following year. For example, an increase of the mycoparasite Ampelomyces quisqualis was noticed in 2017 on grapes that carried the causal agent of powdery mildew, Erysiphe necator, in 2016, thus, amplifying the importance of vineyard microbiota knowledge for disease management and winemaking.

Year, Location, and Variety Impact on Grape-, Soil-, and Leaf-Associated Fungal Microbiota of Arkansas-Grown Table Grapes

With the recent advancement of next-generation sequencing methods, there has been an increase in studies on identification of vineyard microbiota, winery-associated microbiota, and microbiota in wine fermentation. However, there have been few studies investigating the fungal microbiota of table grapes which present distinct spoilage and food safety challenges. The aims of this study were to identify and compare the impact of year, variety, and vineyard location on grape, leaf, and soil fungal communities of two varieties of table grapes, Faith and Gratitude, grown in two open-air vineyards and one high tunnel vineyard. The grape, leaf, and soil mycobiota were analyzed using high throughput amplicon sequencing of the ITS region. The sampling year and location of table grapes had an impact on grape, leaf, and soil mycobiota. Fungal diversity of grape, leaf, and soil was greater in 2017 than in 2016. Grape and leaf samples presented strong similarities in fungal communities with abundance of Sporidiobolaceae and Filobasidium in two vineyards and Cladosporium in another one. The high tunnel structure had distinct grape and leaf fungal communities compared to the two other vineyard locations. Mortierella was the predominant genus (27%) in soil samples for the three locations; however, genera of lower abundance varied between locations. These results provide extensive description of fungal communities in less-studied table grape vineyards and high tunnels, providing useful insight of potential threats and preventive strategies to help improve the production and marketability of table grapes.

Application of MALDI-TOF analysis to reveal diversity and dynamics of winemaking yeast species in wild-fermented, organically produced, New Zealand Pinot Noir wine

Rapid yeast identification is of particular importance in monitoring wine fermentation and assessing strain application in winemaking. We used MALDI-TOF MS analysis supported by 26 S rRNA gene sequence analysis and Saccharomyces-specific PCR testing to differentiate reference and field strains recovered from organic wine production facilities in Waipara, New Zealand, in which Pinot Noir wine was produced by spontaneous fermentations in the vineyard and in the winery. Strains were isolated from each of four key stages of each ferment to evaluate changes in taxonomic diversity. MALDI-TOF MS analysis was confirmed as an excellent yeast identification method, with even closely related Saccharomyces species readily distinguished. A total of 13 indigenous species belonging to eight genera were identified from Pinot Noir ferments, with taxonomic diversity generally reducing as fermentation progressed. However, differences between the taxa recovered were observed between the vineyard and winery ferments, despite the grapes used being from the same batch. Furthermore, some consistent proteomic differences between strains of S. cerevisiae, Hanseniasporum uvarum, Candida californica, Pichia membranifaciens and Starmerella bacillaris correlated with the different fermentation systems used. The high speed, low cost, taxonomic resolution and ability to characterise subtle changes in phenotype that may result from variations in environmental conditions makes MALDI-TOF analysis an attractive tool for further and wider applications in the wine industry. Such applications may include monitoring wine fermentation to actively support the consistency of high-quality wine products, and potentially for the development of such products too.

Occurrence and impact of fungicides residues on fermentation during wine production- A review

Continuous fungicide spraying is required to eliminate fungal pathogens on grapes. However, this practice is associated with several risks, including contamination and environmental imbalance, as well as toxicity to operators and the induction of resistance in pathogens. In addition, a strong correlation has been reported between the presence of fungicides and the occurrence of issues during alcoholic fermentation, resulting in negative impacts on the sensory quality of the final products. Numerous studies have evaluated residue concentrations of phytosanitary products in grapes, juices, and wines, and a significant number of studies have assessed the impact of different agrochemicals on bioprocesses. However, a review compiling the key results of these studies is currently lacking. This review incorporates results obtained in the last decade from research on the presence of fungicide residues, including azoxystrobin, boscalid, captan, copper, fenhexamid, folpet, pyraclostrobin, pyrimethanil and tebuconazole, and their effects on fermentation kinetics. Practical solutions to mitigate these problems, both in vineyards and industry, are also presented and discussed. This review highlights the constant high fungicidal agent concentrations (greater than 1 or 2 mg L^-1) used throughout the winemaking process, with the impact of residues being of particular concern, especially with regard to their effect on yeast activity and the fermentation process. Thus, the adoption of methodologies that allow winemakers to control and trace these residues is an important step in avoiding or reducing fermentation problems throughout the winemaking process.[Figure: see text].

Unravelling the Impact of Grape Washing, SO2, and Multi-Starter Inoculation in Lab-Scale Vinification Trials of Withered Black Grapes

Wine quality is strongly affected by chemical composition and microbial population of grape must, which, in turn, are influenced by several post-harvest treatments, including grape withering. Different strategies have been suggested to manage the fermenting must microbiota, as it plays a central role in the outcomes of both spontaneous and guided fermentations. This study aimed at evaluating the impact of grape washing, SO2 addition, and selected starter culture inoculation on population dynamics, fermentation kinetics, and main oenological parameters in lab-scale trials, focusing on withered grapes usually used for Amarone production. Although grape washing treatment was effective in removing heavy metals and undesirable microorganisms from grape berry surface, inoculation of multi-starter cultures impacted more fermentation rates. Further, both grape washing and starter inoculation procedures had a remarkable impact on wine chemical characteristics, while 30 mg/L SO2 addition did not significantly affect the fermentation process. In summary, the best strategy in terms of limiting off-flavors and potentially reducing the need for SO2 addition in wine from withered grapes was the use of yeast starters, particularly mixed cultures composed by selected strains of Metschnikowia spp. and Saccharomyces cerevisiae. Application of a washing step before winemaking showed a potential to improve organoleptic characteristics of wine.

Capturing yeast associated with grapes and spontaneous fermentations of the Negro Saurí minority variety from an experimental vineyard near León

‘Microbial terroir’ relates to the influence of autochthonous yeasts associated with a grape cultivar on the resultant wine. Geographic region, vineyard site and topography, climate and vintage influence the biodiversity of these microbial communities. Current research focus attempts to correlate their ‘microbial fingerprint’ to the sensorial and chemical characteristics of varietal wines from distinct geographical wine regions. This study focuses on the minor red grape variety, Negro Saurí, which has seen a resurgence in the León Appellation of Origin in Spain as a varietal wine. An experimental vineyard at Melgarajo S.A. (42° 15′ 48.68_N 5° 9′ 56.66_W) was sampled over four consecutive vintages, with autochthonous yeasts being isolated from grapes, must and pilot-scale un-inoculated fermentations, and identified by ITS sequencing. Forty-nine isolates belonging to Metschnikowia pulcherrima, Lachancea thermotolerans, Hanseniaspora uvarum and Torulaspora delbrueckii were isolated from grapes and must, and early stages of fermentation dependent on seasonal variation. Saccharomyces cerevisiae predominated throughout fermentation, as a heterogeneous and dynamic population, with seven major biotypes identified amongst 110 isolates across four consecutive vintages. Twenty-four S. cerevisiae isolates representing five strains dominated in two or more vintages. Their persistence through fermentation warrants further validation of their oenological properties as starter cultures.

Unusual Non-Saccharomyces Yeasts Isolated from Unripened Grapes without Antifungal Treatments

There a lot of studies including the use of non-Saccharomyces yeasts in the process of wine fermentation. The attention is focused on the first steps of fermentation. However, the processes and changes that the non-Saccharomyces yeast populations may have suffered during the different stages of grape berry ripening, caused by several environmental factors, including antifungal treatments, have not been considered in depth. In our study, we have monitored the population dynamics of non-Saccharomyces yeasts during the ripening process, both with biochemical identification systems (API 20C AUX and API ID 32C), molecular techniques (RFLP-PCR) and enzymatic analyses. Some unusual non-Saccharomyces yeasts have been identified (Metschnikowia pulcherrima, Aureobasidium pullulans, Cryptococcus sp. and Rhodotorula mucilaginosa). These yeasts could be affected by antifungal treatments used in wineries, and this fact could explain the novelty involved in their isolation and identification. These yeasts can be a novel source for novel biotechnological uses to be explored in future work.

Impact of Chemical and Alternative Fungicides Applied to Grapevine cv Nebbiolo on Microbial Ecology and Chemical-Physical Grape Characteristics at Harvest

Viticulture is a cropping system in which treatment against fungal diseases (in particular powdery and downy mildews) can be extremely frequent. Accordingly, a reduction in antimicrobial treatments and the application of environmentally-friendly compounds are becoming increasingly important for a more sustainable viticulture. In addition to their effect against pathogens, the impact of these products on the quality of the grapes is very important for the oenological industries, but unfortunately at present few data are available. We evaluated the effect of the application of biocontrol products and resistance inducers in the vineyard on the mechanical properties, microbial ecology, technological and phenolic maturity of Vitis vinifera "Nebbiolo" grapes at harvest. The yield and vigor of vines were not influenced by the treatments, nor were the production of primary and secondary metabolites. However, the active ingredients influenced the mechanical properties of the skin (hardness and thickness). A significant hardening of the skin was detected when laminarin and chito-oligosaccharides were used, and sulfur induced a thickening of the skin with potential consequences for wine quality. Furthermore, the yeast community present on grape berries was influenced by the treatments. The abundance of Aureobasidium pullulans, the dominant species on the grape berry, changed in response to the compounds used. In addition, Alternaria sp. was reduced in some treatments with a potentially positive effect on the quality and the safety of the grapes. This study provides an overview of the effect of biocontrol products and resistance inducers on microbial ecology and "Nebbiolo" grape quality, contributing to the establishment of more sustainable and effective defense strategies in viticulture.