Effect of yeast assimilable nitrogen on the synthesis of phenolic aroma compounds byHanseniaspora vineaestrains

Advancements and challenges for brewing aroma-enhancement fruit wines: Microbial metabolizing and brewing techniques

Aroma, a principal determinant of consumer preference for fruit wines, has recently garnered much attention. Fruit wines brewing was concomitant with complex biochemical reactions, in which a variety of compounds jointly contribute to the aroma quality. To date, the mechanisms underlying the synthesis of aroma compounds and biological regulation methods in fruit wines have remained ambiguous, hindering the further improvement of fruit wines sensory profiles. This review provides a detailed account of the synthesis and regulatory mechanisms of typical aroma compounds and their contributions to the characteristics of wines. Additionally, Comprehensive involves between microflora and the formation of aroma compounds have been emphasized. The microflora-mediated aroma compounds evolution can be controlled by key fermentation techniques to protect and enhance. Meanwhile, the genes impacting key aroma compounds can be identified, which provide references for the rapid screening of aroma-enhanced strains as well as target formation of aroma by modifying relative genes.

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.

Influence of climatic variation on microbial communities during organic Pinot noir wine production

To assess the possible impact of climatic variation on microbial community composition in organic winemaking, we employed a metabarcoding approach to scrutinize the microbiome in a commercial, organic, Pinot noir wine production system that utilizes autochthonous fermentation. We assessed microbial composition across two vintages (2018 and 2021) using biological replicates co-located at the same winery. Microbial dynamics were monitored over four important fermentation time points and correlated with contemporaneous climate data. Bacterial (RANOSIM = 0.4743, p = 0.0001) and fungal (RANOSIM = 0.4738, p = 0.0001) compositions were different in both vintages. For bacteria, Lactococcus dominated the diversity associated with the 2018 vintage, while Tatumella dominated the 2021 vintage. For fungal populations, while Saccharomyces were abundant in both vintages, key differences included Starmerella, copious in the 2018 vintage; and Metschnikowia, substantive in the 2021 vintage. Ordination plots correlated the climatic variables with microbial population differences, indicating temperature as a particularly important influence; humidity values also differed significantly between these vintages. Our data illustrates how climatic conditions may influence microbial diversity during winemaking, and further highlights the effect climate change could have on wine production.

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.

Secondary Aroma: Influence of Wine Microorganisms in Their Aroma Profile

Aroma profile is one of the main features for the acceptance of wine. Yeasts and bacteria are the responsible organisms to carry out both, alcoholic and malolactic fermentation. Alcoholic fermentation is in turn, responsible for transforming grape juice into wine and providing secondary aromas. Secondary aroma can be influenced by different factors; however, the influence of the microorganisms is one of the main agents affecting final wine aroma profile. Saccharomyces cerevisiae has historically been the most used yeast for winemaking process for its specific characteristics: high fermentative metabolism and kinetics, low acetic acid production, resistance to high levels of sugar, ethanol, sulfur dioxide and also, the production of pleasant aromatic compounds. Nevertheless, in the last years, the use of non-saccharomyces yeasts has been progressively growing according to their capacity to enhance aroma complexity and interact with S. cerevisiae, especially in mixed cultures. Hence, this review article is aimed at associating the main secondary aroma compounds present in wine with the microorganisms involved in the spontaneous and guided fermentations, as well as an approach to the strain variability of species, the genetic modifications that can occur and their relevance to wine aroma construction.

Genetic and transcriptomic evidences suggest ARO10 genes are involved in benzenoid biosynthesis by yeast

Benzenoids are compounds associated with floral and fruity flavours in flowers, fruits and leaves and present a role in hormonal signalling in plants. These molecules are produced by the phenyl ammonia lyase pathway. However, some yeasts can also synthesize them from aromatic amino acids using an alternative pathway that remains unknown. Hanseniaspora vineae can produce benzenoids at levels up to two orders of magnitude higher than Saccharomyces species, so it is a model microorganism for studying benzenoid biosynthesis pathways in yeast. According to their genomes, several enzymes have been proposed to be involved in a mandelate pathway similar to that described for some prokaryotic cells. Among them, the ARO10 gene product could present benzoylformate decarboxylase activity. This enzyme catalyses the decarboxylation of benzoylformate into benzaldehyde at the end of the mandelate pathway in benzyl alcohol formation. Two homologous genes of ARO10 were found in the two sequenced H. vineae strains. In this study, nine other H. vineae strains were analysed to detect the presence and per cent homology of ARO10 sequences by PCR using specific primers designed for this species. Also, the copy number of the genes was estimated by quantitative PCR. To verify the relation of ARO10 with the production of benzyl alcohol during fermentation, a deletion mutant in the ARO10 gene of Saccharomyces cerevisiae was used. The two HvARO10 paralogues were analysed and compared with other α-ketoacid decarboxylases at the sequence and structural level.

Non-Saccharomyces in Winemaking: Source of Mannoproteins, Nitrogen, Enzymes, and Antimicrobial Compounds

Traditionally, non-Saccharomyces yeasts have been considered contaminants because of their high production of metabolites with negative connotations in wine. This aspect has been changing in recent years due to an increased interest in the use of these yeasts in the winemaking process. The majority of these yeasts have a low fermentation power, being used in mixed fermentations with Saccharomyces cerevisiae due to their ability to produce metabolites of enological interest, such as glycerol, fatty acids, organic acids, esters, higher alcohols, stable pigments, among others. Additionally, existing literature reports various compounds derived from the cellular structure of non-Saccharomyces yeasts with benefits in the winemaking process, such as polysaccharides, proteins, enzymes, peptides, amino acids, or antimicrobial compounds, some of which, besides contributing to improving the quality of the wine, can be used as a source of nitrogen for the fermentation yeasts. These compounds can be produced exogenously, and later incorporated into the winemaking process, or be uptake directly by S. cerevisiae from the fermentation medium after their release via lysis of non-Saccharomyces yeasts in sequential fermentations.

Genome-wide identification, characterization and expression analysis of lineage-specific genes within Hanseniaspora yeasts

Lineage-specific genes (LSGs) are defined as genes with sequences that are not significantly similar to those in any other lineage. LSGs have been proposed, and sometimes shown, to have significant effects in the evolution of biological function. In this study, two sets of Hanseniaspora spp. LSGs were identified by comparing the sequences of the Kloeckera apiculata genome and of 80 other yeast genomes. This study identified 344 Hanseniaspora-specific genes (HSGs) and 109 genes ('orphan genes') specific to K. apiculata. Three thousand three hundred thirty-one K. apiculata genes that showed significant similarity to at least one sequence outside the Hanseniaspora were classified into evolutionarily conserved genes. We analyzed their sequence features, functional categories, gene origin, gene structure and gene expression. We also investigated the predicted cellular roles and Gene Ontology categories of the LSGs using functional inference. The patterns of the functions of LSGs do not deviate significantly from genome-wide average. The results showed that a few LSGs were formed by gene duplication, followed by rapid sequence divergence. Many of the HSGs and orphan genes exhibited altered expression in response to abiotic stress. Studying these LSGs might be helpful for understanding the molecular mechanism of yeast adaption.

Yeasts for low input winemaking: Microbial terroir and flavor differentiation

Vitis vinifera flowers and grape fruits are one of the most interesting ecosystem niches for native yeasts development. There are more than a 100 yeast species and millions of strains that participate and contribute to design the microbial terroir. The wine terroir concept is understood when grape and wine micro-regions were delimited by different quality characteristics after humans had been growing vines for more than 10,000 years. Environmental conditions, such as climate, soil composition, water management, winds and air quality, altitude, fauna and flora and microbes, are considered part of the "terroir" and contribute to a unique wine style. If "low input winemaking" strategies are applied, the terroir effect will be expected to be more authentic in terms of quality differentiation. Interestingly, the role of the microbial flora associated with vines was very little study until recently when new genetic technologies for massive species identification were developed. These biotechnologies allowed following their environmental changes and their effect in shaping the microbial profiles of different wine regions. In this chapter we explain the interesting positive effects on flavor diversity and wine quality obtained by using "friendly" native yeasts that allowed the microbial terroir flora to participate and contribute during fermentation.

2-Phenylethanol and 2-phenylethylacetate production by nonconventional yeasts using tequila vinasses as a substrate

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Yeast species influenced the de novo synthesis of 2-phenylethylacetate.

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Inhibitory compounds showed a strong influence on cell growth and 2-phenylethylacetate production for the evaluated yeasts.

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More than a 50 % reduction in the chemical and biochemical oxygen demand was achieved by yeast fermentation.

Vinasses from the tequila industry are wastewaters with highly elevated organic loads. Therefore, to obtain value-added products by yeast fermentations, such as 2-phenylethanol (2-PE) and 2-phenylethylacetate (2-PEA), could be interesting for industrial applications from tequila vinasses. In this study, four yeasts species (Wickerhamomyces anomalus, Candida glabrata, Candida utilis, and Candida parapsilosis) were evaluated with two different chemically defined media and tequila vinasses. Differences in the aroma compounds production were observed depending on the medium and yeast species used. In tequila vinasses, the highest concentration (65 mg/L) of 2-PEA was reached by C. glabrata, the inhibitory compounds decreased biomass production and synthesis of 2-PEA, and biochemical and chemical oxygen demands were reduced by more than 50 %. Tequila vinasses were suitable for the production of 2-phenylethylacetate by the shikimate pathway. A metabolic network was developed to obtain a guideline to improve 2-PE and 2-PEA production using flux balance analysis (FBA).

Contribution of Non-Saccharomyces Yeasts to Wine Freshness. A Review

Freshness, although it is a concept difficult to define in wines, can be understood as a combination of different circumstances. Organolepticwise, bluish red, floral and fruity, more acidic and full-bodied wines, are perceived as younger and fresher by consumers. In traditional winemaking processes, these attributes are hard to boost if no other technology or biotechnology is involved. In this regard, the right selection of yeast strains plays an important role in meeting these parameters and obtaining wines with fresher profiles. Another approach in getting fresh wines is through the use of novel non-thermal technologies during winemaking. Herein, the contributions of non-Saccharomyces yeasts and emerging technologies to these parameters are reviewed and discussed.

Assessment of chemical composition and sensorial properties of ciders fermented with different non-Saccharomyces yeasts in pure and mixed fermentations

This work presents the attempt to enhance the flavor complexity of cider fermented by different non-Saccharomyces species. Pichia kluyveri and Hanseniaspora vineae pure cultures were used as reference ciders. Mixed cultures between all 4 species gave 5 fermentations, where Hanseniaspora uvarum or Torulaspora quercuum were included for apple juice fermentation. Chemical composition and sensorial properties of all ciders were studied. The results indicated that the growth of P. kluyveri and H. vineae were interreacted and also affected by H. uvarum and T. quercuum. H. vineae was more capable of consuming sugar than P. kluyveri. Ciders from the single culture fermentation with P. kluyveri (Pk), as well as from mixed fermentation with P. kluyveri and H. uvarum (Pk-Hu), had high residual sugar, sugar/acid ratio, and glucose-fructose consumption ratio. Large shifts in the consumption and production of organic acids and polyphenols among all ciders were observed. The calculation of the relative odor activity value (rOAV) showed that 17 volatile compounds had an rOAV >1 in at least one sample, and acetate esters and ethyl esters were the groups with the highest number of volatile compounds of importance to the cider aroma. Among these 17 compounds, 3-methylbutyl acetate, 2-methylbutyl acetate, ethyl hexanoate, ethyl octanoate, and β-damascenone exhibited high rOAVs in some ciders and might contribute fruity, floral, and sweet features to the cider aroma. Besides, the tropical fruity aroma from 3-methylbutyl acetate was only perceived in Pk and Pk-Hu. The partial least squares regression (PLSR) analysis revealed that acetate esters contributed positively to the roasted and cooked odor of all ciders. This is the first study evaluating simultaneous fermentation of two non-Saccharomyces yeasts to produce cider, which provides new insights into cider production.

The Influence of Non-Saccharomyces Species on Wine Fermentation Quality Parameters

In the past, some microbiological studies have considered most non-Saccharomyces species to be undesirable spoilage microorganisms. For several decades, that belief made the Saccharomyces genus the only option considered by winemakers for achieving the best possible wine quality. Nevertheless, in recent decades, some strains of non-Saccharomyces species have been proven to improve the quality of wine. Non-Saccharomyces species can positively influence quality parameters such as aroma, acidity, color, and food safety. These quality improvements allow winemakers to produce innovative and differentiated wines. For that reason, the yeast strains Torulaspora delbrueckii, Lachancea thermotolerans, Metschnikowia pulcherrima, Schizosaccharomyces pombe, and Pichia kluyveri are now available on the market. Other interesting species, such as Starmerella bacillaris, Meyerozyma guilliermondii, Hanseniospora spp., and others, will probably be available in the near future.

Genomic and Transcriptomic Basis of Hanseniaspora vineae's Impact on Flavor Diversity and Wine Quality

Hanseniaspora is the main genus of the apiculate yeast group that represents approximately 70% of the grape-associated microflora. Hanseniaspora vineae is emerging as a promising species for quality wine production compared to other non-Saccharomyces species. Wines produced by H. vineae with Saccharomyces cerevisiae consistently exhibit more intense fruity flavors and complexity than wines produced by S. cerevisiae alone. In this work, genome sequencing, assembling, and phylogenetic analysis of two strains of H. vineae showed that it is a member of the Saccharomyces complex and it diverged before the whole-genome duplication (WGD) event from this clade. Specific flavor gene duplications and absences were identified in the H. vineae genome compared to 14 fully sequenced industrial S. cerevisiae genomes. The increased formation of 2-phenylethyl acetate and phenylpropanoids such as 2-phenylethyl and benzyl alcohols might be explained by gene duplications of H. vineae aromatic amino acid aminotransferases (ARO8 and ARO9) and phenylpyruvate decarboxylases (ARO10). Transcriptome and aroma profiles under fermentation conditions confirmed these genes were highly expressed at the beginning of stationary phase coupled to the production of their related compounds. The extremely high level of acetate esters produced by H. vineae compared to that by S. cerevisiae is consistent with the identification of six novel proteins with alcohol acetyltransferase (AATase) domains. The absence of the branched-chain amino acid transaminases (BAT2) and acyl coenzyme A (acyl-CoA)/ethanol O-acyltransferases (EEB1) genes correlates with H. vineae's reduced production of branched-chain higher alcohols, fatty acids, and ethyl esters, respectively. Our study provides sustenance for understanding and potentially utilizing genes that determine fermentation aromas.IMPORTANCE The huge diversity of non-Saccharomyces yeasts in grapes is dominated by the apiculate genus Hanseniaspora Two native strains of Hanseniaspora vineae applied to winemaking because of their high oenological potential in aroma and fermentation performance were selected to obtain high-quality genomes. Here, we present a phylogenetic analysis and the complete transcriptome and aroma metabolome of H. vineae during three fermentation steps. This species produced significantly richer flavor compound diversity than Saccharomyces, including benzenoids, phenylpropanoids, and acetate-derived compounds. The identification of six proteins, different from S. cerevisiae ATF, with diverse acetyltransferase domains in H. vineae offers a relevant source of native genetic variants for this enzymatic activity. The discovery of benzenoid synthesis capacity in H. vineae provides a new eukaryotic model to dilucidate an alternative pathway to that catalyzed by plants' phenylalanine lyases.

Grape berry surface bacterial microbiome: impact from the varieties and clones in the same vineyard from central China

AIMS

Bacterial microbiome on grape berry surface may play an important role in grape quality and health. This study aims to investigate the impact of grape varieties and clones on grape berry surface bacterial microbiome from the same vineyard.

METHODS AND RESULTS

High-throughput sequencing strategy was used to investigate the bacterial diversity and abundance on the grape surfaces of 12 clones belonging to six varieties grown in the same vineyard of Zhengzhou Fruit Research Institute in Henan Province. In total, 45 bacterial phyla and 933 genera were detected from all samples. Cyanobacteria, Proteobacteria and Firmicutes were the most abundant and prevalent phyla, while Bacteroidetes, Chloroflexi, Acidobacteria and Planctomycetes were grape clone specific phyla. The nonrank genus from phylum Cyanobacteria occupied 30-81% of grape clones from Italian Riesling (GRX), Cabernet Franc (PLZ), Pinot Blanc (BBN) and Riesling (LSL). Interestingly, Bacillus, Pseudomonas and Lactococcus were the only three prevalent genera found on all the clones. Furthermore, the predicted functional activities of grape surface bacterial communities varied according to the clones.

CONCLUSIONS

The present study revealed that in addition to the grape varieties, the variations in grape clone background may also affect the bacterial microbiome on grape surfaces which may ultimately determine their functional activities.

SIGNIFICANCE AND IMPACT OF THE STUDY

This research provides an important information for grape planting and wine fermentation that not only the grape varieties need to be paid attention but also grape clones from the specific variety need to be concerned.

Oenological Impact of the Hanseniaspora/Kloeckera Yeast Genus on Wines—A Review

Apiculate yeasts of the genus Hanseniaspora/Kloeckera are the main species present on mature grapes and play a significant role at the beginning of fermentation, producing enzymes and aroma compounds that expand the diversity of wine color and flavor. Ten species of the genus Hanseniaspora have been recovered from grapes and are associated in two groups: H. valbyensis, H. guilliermondii, H. uvarum, H. opuntiae, H. thailandica, H. meyeri, and H. clermontiae; and H. vineae, H. osmophila, and H. occidentalis. This review focuses on the application of some strains belonging to this genus in co-fermentation with Saccharomyces cerevisiae that demonstrates their positive contribution to winemaking. Some consistent results have shown more intense flavors and complex, full-bodied wines, compared with wines produced by the use of S. cerevisiae alone. Recent genetic and physiologic studies have improved the knowledge of the Hanseniaspora/Kloeckera species. Significant increases in acetyl esters, benzenoids, and sesquiterpene flavor compounds, and relative decreases in alcohols and acids have been reported, due to different fermentation pathways compared to conventional wine yeasts.

Attraction of Coffee Bean Weevil, Araecerus fasciculatus, to Volatiles from the Industrial Yeast Kluyveromyces lactis

The coffee bean weevil (CBW), Araecerus fasciculatus (De Geer, 1775) (Coleoptera: Anthribidae) is an important pest of stored products such as grains, coffee beans, cassava, and traditional Chinese medicine materials. In China, CBW causes large losses of Daqu, a traditional Chinese liquor fermentation starter, and, unfortunately, the use of conventional insecticides against CBW is not suitable in Daqu storage. We found CBW to be highly attracted to fermenting yeast cultures, such as Kluyveromyces lactis. Eight volatile compounds, produced by fermenting cultures and not by sterile samples, were identified by gas chromatography coupled with mass spectrometry. Five of these substances elicited significant responses in Y-tube behavioral bioassays. Field trapping experiments revealed 2-phenylethanol and 2-phenylethyl acetate to be crucial for attraction of CBW. Results show that yeast volatiles play an important role in host location, and that 2-phenylethanol and 2-phenylethyl acetate could be utilized as potential attractants in monitoring and control systems against this important pest.

Wine microbiology is driven by vineyard and winery anthropogenic factors

The effects of different anthropic activities (vineyard: phytosanitary protection; winery: pressing and sulfiting) on the fungal populations of grape berries were studied. The global diversity of fungal populations (moulds and yeasts) was performed by pyrosequencing. The anthropic activities studied modified fungal diversity. Thus, a decrease in biodiversity was measured for three successive vintages for the grapes of the plot cultivated with Organic protection compared to plots treated with Conventional and Ecophyto protections. The fungal populations were then considerably modified by the pressing‐clarification step. The addition of sulfur dioxide also modified population dynamics and favoured the domination of the species Saccharomyces cerevisiae during fermentation. The non‐targeted chemical analysis of musts and wines by FT‐ICR‐MS showed that the wines could be discriminated at the end of alcoholic fermentation as a function of adding SO₂ or not, but also and above all as a function of phytosanitary protection, regardless of whether these fermentations took place in the presence of SO₂ or not. Thus, the existence of signatures in wines of chemical diversity and microbiology linked to vineyard protection has been highlighted.

De Novo Synthesis of Benzenoid Compounds by the Yeast Hanseniaspora vineae Increases the Flavor Diversity of Wines

Benzyl alcohol and other benzenoid-derived metabolites of particular importance in plants confer floral and fruity flavors to wines. Among the volatile aroma components in Vitis vinifera grape varieties, benzyl alcohol is present in its free and glycosylated forms. These compounds are considered to originate from grapes only and not from fermentative processes. We have found increased levels of benzyl alcohol in red Tannat wine compared to that in grape juice, suggesting de novo formation of this metabolite during vinification. In this work, we show that benzyl alcohol, benzaldehyde, p-hydroxybenzaldehyde, and p-hydroxybenzyl alcohol are synthesized de novo in the absence of grape-derived precursors by Hanseniaspora vineae. Levels of benzyl alcohol produced by 11 different H. vineae strains were 20-200 times higher than those measured in fermentations with Saccharomyces cerevisiae strains. These results show that H. vineae contributes to flavor diversity by increasing grape variety aroma concentration in a chemically defined medium. Feeding experiments with phenylalanine, tryptophan, tyrosine, p-aminobenzoic acid, and ammonium in an artificial medium were tested to evaluate the effect of these compounds either as precursors or as potential pathway regulators for the formation of benzenoid-derived aromas. Genomic analysis shows that the phenylalanine ammonia-lyase (PAL) and tyrosine ammonia lyase (TAL) pathways, used by plants to generate benzyl alcohols from aromatic amino acids, are absent in the H. vineae genome. Consequently, alternative pathways derived from chorismate with mandelate as an intermediate are discussed.