Population and oenological characteristics of non-Saccharomyces yeasts associated with grapes of Northwestern Argentina

Regional aroma characteristics of spontaneously fermented Cabernet Sauvignon wines produced from seven sub-regions in Shangri-La of China

Shangri-La is a promising wine region in China, which has great potential for producing high-quality wines with distinctive regional characteristics. In this work, the aroma properties of spontaneously fermented Cabernet Sauvignon wines produced from seven sub-regions of Shangri-La (Adong, Liutongjiang, Sinong, Xidang, and Nitong from Lancang River basin; Benzilan and Dari from Jinsha River Basin) were comprehensively analyzed using the headspace micro-extraction with gas chromatography-mass spectrometry, odor activity values, and olfactory evaluation. Results showed that a total of 59 volatiles belonging to seven groups were identified and quantified in all regional wines, with alcohols constituting the most abundant group, followed by esters and volatile fatty acids. Based on their odor activity values, six alcohols, seven esters, two terpenes, one C13-norisoprenoids, and three volatile fatty acids were identified as key volatiles which significantly contribute to the aroma of these wines. Principal component analysis showed the distinct compositions of these 19 key volatiles among the seven regional wines. Olfactory evaluation revealed certain differences in aroma profiles, particularly "Tropical fruit", "Dried fruit", "Vegetal", and "Sweet" among them. This study enhances our understanding on the unique terroir flavors of Shangri-La wines and is helpful for further producing high-quality wines with regional characteristics.

Yeast Diversity in Wine Grapes from Japanese Vineyards and Enological Traits of Indigenous Saccharomyces cerevisiae Strains

Japan has numerous vineyards with distinct geographical and climatic conditions. To the best of our knowledge, there is no comprehensive analysis of the diversity of yeasts associated with wine grapes from Japan. This study aimed to determine yeast diversity in wine grapes from four wine-producing regions in Japan and to evaluate the physicochemical characteristics of wines produced with indigenous Saccharomyces cerevisiae strains isolated from two regions. A total of 2648 strains were isolated from nine wine grape samples. MALDI-TOF MS and 26S rDNA sequence analyses revealed that the strains belonged to 21 non-Saccharomyces yeasts and 1 Saccharomyces yeast (S. cerevisiae). Non-Saccharomyces yeasts were found in high quantities and were highly distributed among the wine grape samples. Differences in the distribution of the identified yeast species were noted among the different wine grape varieties and regions. Indigenous S. cerevisiae strains of different genotypes from different regions exhibit distinct physiological traits. Our findings are expected to enhance our understanding of the local yeasts associated with Japanese vineyards and contribute to obtaining cultures that can provide region-specific organoleptic characteristics to local wines produced in Japan.

Exploring future applications of the apiculate yeast Hanseniaspora

As a metaphor, lemons get a bad rap; however the proverb 'if life gives you lemons, make lemonade' is often used in a motivational context. The same could be said of Hanseniaspora in winemaking. Despite its predominance in vineyards and grape must, this lemon-shaped yeast is underappreciated in terms of its contribution to the overall sensory profile of fine wine. Species belonging to this apiculate yeast are known for being common isolates not just on grape berries, but on many other fruits. They play a critical role in the early stages of a fermentation and can influence the quality of the final product. Their deliberate addition within mixed-culture fermentations shows promise in adding to the complexity of a wine and thus provide sensorial benefits. Hanseniaspora species are also key participants in the fermentations of a variety of other foodstuffs ranging from chocolate to apple cider. Outside of their role in fermentation, Hanseniaspora species have attractive biotechnological possibilities as revealed through studies on biocontrol potential, use as a whole-cell biocatalyst and important interactions with Drosophila flies. The growing amount of 'omics data on Hanseniaspora is revealing interesting features of the genus that sets it apart from the other Ascomycetes. This review collates the fields of research conducted on this apiculate yeast genus.

Isolation and identification of native yeasts from the spontaneous fermentation of grape musts

Recently, there has been growing interest in the characterization of native yeasts for their use in production of wines with regional characteristics. This study aimed to investigate Saccharomyces and non-Saccharomyces yeasts present in the spontaneous fermentation of Tannat and Marselan grape musts collected from Concordia (Entre Ríos, Argentina) over 2019, 2020, and 2021 vintages. The evolution of these fermentative processes was carried out by measuring total soluble solids, total acidity, volatile acidity, pH, ethanol concentration, and total carbon content. Isolated Saccharomyces and non-Saccharomyces yeasts were identified based on colony morphology in WL medium, 5.8S-ITS-RFLP analysis, and 26S rDNA D1/D2 gene sequencing. Two hundred and ten yeast colonies were isolated and identified as Pichia kudriavzevii, Saccharomyces cerevisiae, Hanseniaspora uvarum, Metschnikowia pulcherrima, Candida albicans, Candida parapsilosis, Pichia occidentalis, Pichia bruneiensis, Hanseniaspora opuntiae, Issatchenkia terricola, and Hanseniaspora vineae. P. kudriavzevii isolated from all vintages was associated with the spontaneous fermentation of grape musts from the Concordia region.

Survey of the yeast ecology of dehydrated grapes and strain selection for wine fermentation

In this study we investigated the yeast population present on partially dehydrated Nebbiolo grapes destined for 'Sforzato di Valtellina', with the aim to select indigenous starters suitable for the production of this wine. Yeasts were enumerated, isolated, and identified by molecular methods (5.8S-ITS-RFLP and D1/D2 domain sequencing). A genetic, physiological (ethanol and sulphur dioxide tolerance, potentially useful enzymatic activities, hydrogen sulphide production, adhesive properties, and killer activity) and oenological (laboratory pure micro-fermentations) characterization was also carried out. Based on relevant physiological features, seven non-Saccharomyces strains were chosen for laboratory-scale fermentations, either in pure or in mixed-culture (simultaneous and sequential inoculum) with a commercial Saccharomyces cerevisiae strain. Finally, the best couples and inoculation strategy were further tested in mixed fermentations in winery. In both laboratory and winery, microbiological and chemical analyses were conducted during fermentation. The most abundant species on grapes were Hanseniaspora uvarum (27.4 % of the isolates), followed by Metschnikowia spp. (21.0 %) and Starmerella bacillaris (12.9 %). Technological characterization highlighted several inter- and intra-species differences. The best oenological aptitude was highlighted for species Starm. bacillaris, Metschnikowia spp., Pichia kluyveri and Zygosaccharomyces bailli. The best fermentation performances in laboratory-scale fermentations were found for Starm. bacillaris and P. kluyveri, due to their ability to reduce ethanol (-0.34 % v/v) and enhance glycerol production (+0.46 g/L). This behavior was further confirmed in winery. Results of this study contribute to the knowledge of yeast communities associated with a specific environment, like those of Valtellina wine region.

The Use of Hanseniaspora occidentalis in a Sequential Must Inoculation to Reduce the Malic Acid Content of Wine

In this study, the impact of the apiculate yeast Hanseniaspora occidentalis as a co-partner with Saccharomyces cerevisiae was investigated in a sequential-type mixed-culture fermentation of Muscaris grape must. As with other fermentation trials using Hanseniaspora strains, a significant increase in ethyl acetate was observed, but most intriguing was the almost complete abolition of malic acid (from 2.0 g/L to 0.1 g/L) in the wine. Compared to the pure S. cerevisiae inoculum, there was also a marked increase in the concentrations of the other acetate esters. Modulation of some of the varietal elements, such as rose oxide, was also observed. This work shows the promising use of H. occidentalis in a mixed-culture must fermentation, especially in the acid modulation of fruit juice matrices.

Evaluation of Four Indigenous Non-Saccharomyces Yeasts Isolated from the Shangri-La Wine Region (China) for Their Fermentation Performances and Aroma Compositions in Synthetic Grape Juice Fermentation

This study investigated the fermentation performances and aroma compositions of synthetic grape juice that was fermented by four indigenous non-Saccharomyces yeast isolates that were obtained from the Shangri-La wine region (China): Meyerozyma guilliermondii (AD-58), Saccharomycopsis vini (BZL-28), Saturnispora diversa (BZL-11), and Wickerhamomyces anomalus (DR-110), in comparison to those of Saccharomyces cerevisiae (EC1118). The four indigenous non-Saccharomyces yeasts showed a lower fermentative capacity and a lower conversion rate of sugar to alcohol, but a higher yield of volatile acidity. W. anomalus (DR-110) had a greater ability to produce numerous esters and short-chain fatty acids and the representative flavors of its fermented medium were fruity and fatty. Sac. vini (BZL-28), interestingly, exhibited great capacity in the formation of many monoterpenes, particularly (Z)-β-ocimene, E-β-ocimene, linalool, citral, and geraniol and its fermented medium was characterized by a strong fruity (citrus-like) and floral flavor. M. guilliermondii (AD-58) and Sat. diversa (BZL-11) only mildly affected the aroma profiles of their resultant fermented media, since the concentrations of most of the volatiles that were produced by these two isolates were much lower than their sensory thresholds. The four indigenous non-Saccharomyces yeasts exhibited distinctive fermentation performances and aroma production behaviors. In particularly, W. anomalus (DR-110) and Sac. vini (BZL-28) have shown good potential in enhancing the aromas and complexity of wine.

Diversity of non-Saccharomyces yeasts of grape berry surfaces from representative Cabernet Sauvignon vineyards in Henan Province, China

Non-Saccharomyces yeasts are important players during winemaking and may come from grapes grown in vineyards. To study the diversity of non-Saccharomyces yeasts on surface grape berries, 433 strains were isolated from different Cabernet Sauvignon vineyards grown in Henan Province. Our results demonstrated that these strains were classified into 16 morphotypes according to their growth morphology on Wallerstein Laboratory agar medium, and were identified as seven species from four genera: Hanseniaspora opuntiae, Hanseniaspora vineae, Hanseniaspora uvarum, Pichia occidentalis, Pichia kluyveri, Issatchenkia terricola and Saturnispora diversa based on a series of molecular biological experiments. Hanseniaspora opuntiae was obtained from all sampling sites except Changyuan County, while Pichia kluyveri and Saturnispora diversa were only found in sites of Zhengzhou Grape Resource Garden and Minquan County, respectively. The site Minquan was home of the greatest species richness while only one single species (Hanseniaspora opuntiae) was detected at NAPA winery from Zhengzhou or at Anyang County. Finally, this study suggested that the geographic distribution and diversity of non-Saccharomyces yeast populations on Cabernet Sauvignon grape berries were likely to be determined by a combination of grape varieties and environmental factors.

Biodiversity of non-Saccharomyces yeasts associated with spontaneous fermentation of Cabernet Sauvignon wines from Shangri-La wine region, China

Shangri-La is a wine region that has the highest altitude vineyards in China. This is the first study investigated the biodiversity of non-Saccharomyces yeasts associated with spontaneous fermentation of Cabernet Sauvignon wines produced from two sub-regions (Lancang River and Jinsha River) of Shangri-La. The culturable yeasts were preliminarily classified based on their colonial morphology on the Wallerstein Laboratory nutrient agar plates. Yeast species were identified by the sequencing of the 26S rRNA D1/D2 region and the 5.8S rRNA ITS region. Twenty-five non-Saccharomyces yeast species belonging to sixteen genera were isolated and identified in Shangri-La wine region. Candida, Hanseniaspora, Pichia, and Starmerella were found in both sub-regions, but the Lancang River showed more diverse yeast species than the Jinsha River. Shangri-La not only exhibited high diversity of non-Saccharomyces yeasts, and furthermore, seven species of non-Saccharomyces yeasts were exclusively found in this region, including B. bruxellensis, D. hansenii, M. guilliermondii, S. vini, S. diversa, T. delbrueckii and W. anomalus, which might play an important role in distinctive regional wine characteristics. This study provide a relatively comprehensive analysis of indigenous non-Saccharomyces yeasts associated with Cabernet Sauvignon from Shangri-La, and has significance for exploring 'microbial terroir' of wine regions in China.

Saccharomyces cerevisiae and Hanseniaspora uvarum mixed starter cultures: Influence of microbial/physical interactions on wine characteristics

The growing trend in the wine industry is the revaluation of the role of non-Saccharomyces yeasts, promoting the use of these yeasts in association with Saccharomyces cerevisiae. Non-Saccharomyces yeasts contribute to improve wine complexity and organoleptic composition. However, the use of mixed starters needs to better understand the effect of the interaction between these species during alcoholic fermentation. The aim of this study is to evaluate the influence of mixed starter cultures, composed by combination of different S. cerevisiae and Hanseniaspora uvarum strains, on wine characteristics and to investigate the role of cell-to-cell contact on the metabolites produced during alcoholic fermentation. In the first step, three H. uvarum and two S. cerevisiae strains, previously selected, were tested during mixed fermentations in natural red grape must in order to evaluate yeast population dynamics during inoculated fermentation and influence of mixed starter cultures on wine quality. One selected mixed starter was tested in a double-compartment fermentor in order to compare mixed inoculations of S. cerevisiae/H. uvarum with and without physical separation. Our results revealed that physical contact between S. cerevisiae and H. uvarum affected the viability of H. uvarum strain, influencing also the metabolic behaviour of the strains. Although different researches are available on the role of cell-to-cell contact-mediated interactions on cell viability of the strains included in the mixed starter, to our knowledge, very few studies have evaluated the influence of cell-to-cell contact on the chemical characteristics of wine.

The Genus Metschnikowia in Enology

Over the last decade, several non-Saccharomyces species have been used as an alternative yeast for producing wines with sensorial properties that are distinctive in comparison to those produced using only Saccharomycescerevisiae as the classical inoculum. Among the non-Saccharomyces wine yeasts, Metschnikowia is one of the most investigated genera due to its widespread occurrence and its impact in winemaking, and it has been found in grapevine phyllospheres, fruit flies, grapes, and wine fermentations as being part of the resident microbiota of wineries and wine-making equipment. The versatility that allows some Metschnikowia species to be used for winemaking relies on an ability to grow in combination with other yeast species, such as S. cerevisiae, during the first stages of wine fermentation, thereby modulating the synthesis of secondary metabolites during fermentation in order to improve the sensory profile of the wine. Metschnikowia exerts a moderate fermentation power, some interesting enzymatic activities involving aromatic and color precursors, and potential antimicrobial activity against spoilage yeasts and fungi, resulting in this yeast being considered an interesting tool for use in the improvement of wine quality. The abovementioned properties have mostly been determined from studies on Metschnikowia pulcherrima wine strains. However, M. fructicola and M. viticola have also recently been studied for winemaking purposes.