Biocontrol strategies against Botrytis cinerea in viticulture: evaluating the efficacy and mode of action of selected winemaking yeast strains.

Botrytis cinerea poses a recurring threat to viticulture, causing significant yield losses each year. The study explored the biocontrol capabilities of commercially used winemaking yeasts as a strategy to manage B. cinerea in grape berries. The winemaking yeast strains-Saccharomyces cerevisiae ES181, Saccharomyces pastorianus KBG6, S. cerevisiae BCS103, Lachancea thermotolerans Omega, and Torulaspora delbrueckii TD291-reduced B. cinerea growth and conidiation in vitro. Furthermore, they demonstrated a decreased disease severity and number of conidia in grape berries. Among these strains, S. cerevisiae BCS103 was the most effective, inducing the expression of the defense-related gene PR4 in berries. Its diffusible compounds and volatile organic compounds also reduced the expression of BcLTF2, a positive regulator of B. cinerea conidiogenesis. The examined winemaking yeast strains, especially S. cerevisiae BCS103, demonstrated effective inhibition of B. cinerea in vitro and in grape berries, influencing key defense genes and reducing BcLTF2 expression, offering potential solutions for disease management in viticulture. The study underscores the promise of commercially available winemaking yeast strains as eco-friendly tools against B. cinerea in viticulture. Leveraging their safety and existing use in winemaking offers a potential avenue for sustainable disease management.

A comparative study to investigate the individual contribution of metabolic and physical interaction on volatiles formation in the mixed fermentation of Torulaspora delbrueckii and Saccharomyces cerevisiae.

It is well-known that the co-inoculation of Saccharomyces cerevisiae and non-Saccharomyces strains can modulate and improve the aromatic quality of wine through their multi-level interactions. However, the individual contribution of metabolic interaction (MI) and physical interaction (PI) on wine volatiles remains poorly understood. In this work, we utilized a double-compartment bioreactor to examine the aromatic effect of MI and PI by comparing the volatiles production in Torulaspora delbrueckii and Saccharomyces cerevisiae single fermentations to their mixed fermentations with or without physical separation. Results showed that the PI between T. delbrueckii and S. cerevisiae increased the production of most aroma compounds, especially for acetate esters and volatile fatty acids. In comparison, the MI only promoted a few volatile compounds, including ethyl decanoate, isoamyl acetate, and isobutanol. Noticeably, the MI significantly decreased the levels of ethyl dodecanoate, 2-phenylethyl alcohol, and decanoic acid, which exhibited opposite profiles in PI. Our results indicated that the PI was mainly responsible for the improved volatiles in T. delbrueckii/S. cerevisiae mixed fermentation, while the MI can be targeted to modulate the specific aroma compounds. A thorough understanding of the PI and MI aromatic effect will empower winemakers to accurately and directionally control the volatile profile of the wine, promoting the application of multi-starters to produce diverse styles of wines.

Effects of Torulaspora delbrueckii and Saccharomyces cerevisiae Co-Fermentation on the Physicochemical and Flavor Compounds of Huaniu Apple Cider.

The effects of different fermentation methods utilizing Torulaspora delbrueckii 1004 and Saccharomyces cerevisiae 32169 on the physicochemical properties, organic acid content, polyphenol and flavonoid concentrations, antioxidant activity, and volatile aroma compounds of Huaniu apple cider were investigated in this study. Employing methods of single inoculation, co-inoculation, and sequential inoculation, it was found that sequential fermentation exhibited strong fermentative power in the initial stages, effectively reducing the content of soluble solids and achieving a balanced composition of malic, succinic, and citric acids while maintaining a lower titratable acidity. Sequential inoculation was observed to significantly enhance the total polyphenols and flavonoids, as well as the antioxidant capacity (p < 0.05). Specifically, in the synthesis of volatile aroma compounds, sequential inoculation significantly enhanced the richness and diversity of the Huaniu apple cider's aromas, particularly in terms of the concentration of ester compounds (p < 0.05). Principal component analysis further confirmed the superiority of sequential inoculation in terms of aroma component diversity and richness. The findings of this study suggest that sequential inoculation of fermentation with non-Saccharomyces and S. cerevisiae is an effective strategy for optimizing the flavor characteristics of Huaniu apple cider, offering valuable theoretical support and practical guidance for enhancing cider quality and fostering the development of new products.

Sequential inoculation of flocculent Torulaspora delbrueckii with Saccharomyces cerevisiae increases color density of Pinot Noir wines.

Pinot noir grapes require careful management in the winery to prevent loss of color density and promote aging stability. Winemaking with flocculent yeast has been shown to increase color density, which is desirable to consumers. This research explored interspecies sequential inoculation and co-flocculation of commercial yeast on Pinot noir wine color. Sedimentation rates of six non-Saccharomyces species and two Saccharomyces cerevisiae strains were assayed individually and in combination. The most flocculent pairings, Torulaspora delbrueckii BIODIVA with S. cerevisiae RC212 or VL3, were used to ferment 20 L Pinot noir must. Sequential fermentations produced wines with greater color density at 420 + 520 nm, confirmed by sensory panel. Total and monomeric anthocyanin concentrations were decreased in sequentially fermented wines, despite being the main source of red wine color. BIODIVA adsorbed more anthocyanins than S. cerevisiae, indicating a greater number of cell wall mannoproteins in flocculent yeast, that could then result in a later release of anthocyanins and enhance copigment formation in red wines.

A glimpse at an early stage of microbe domestication revealed in the variable genome of Torulaspora delbrueckii, an emergent industrial yeast.

Microbe domestication has a major applied relevance but is still poorly understood from an evolutionary perspective. The yeast Torulaspora delbrueckii is gaining importance for biotechnology but little is known about its population structure, variation in gene content or possible domestication routes. Here, we show that T. delbrueckii is composed of five major clades. Among the three European clades, a lineage associated with the wild arboreal niche is sister to the two other lineages that are linked to anthropic environments, one to wine fermentations and the other to diverse sources including dairy products and bread dough (Mix-Anthropic clade). Using 64 genomes we assembled the pangenome and the variable genome of T. delbrueckii. A comparison with Saccharomyces cerevisiae indicated that the weight of the variable genome in the pangenome of T. delbrueckii is considerably smaller. An association of gene content and ecology supported the hypothesis that the Mix-Anthropic clade has the most specialized genome and indicated that some of the exclusive genes were implicated in galactose and maltose utilization. More detailed analyses traced the acquisition of a cluster of GAL genes in strains associated with dairy products and the expansion and functional diversification of MAL genes in strains isolated from bread dough. In contrast to S. cerevisiae, domestication in T. delbrueckii is not primarily driven by alcoholic fermentation but rather by adaptation to dairy and bread-production niches. This study expands our views on the processes of microbe domestication and on the trajectories leading to adaptation to anthropic niches.

The influence of Torulaspora delbrueckii on beer fermentation.

In this study, the effect of five different Torulaspora delbrueckii strains in combination with an ale type Saccharomyces cerevisiae on physical, chemical, microbiological, aroma composition, and sensory profiles of beer were examined. The ethyl alcohol content of produced beers ranged from 5.46% (v/v) to 5.93% (v/v), while the highest alcohol amount was obtained using a pure culture of S. cerevisiae. The major volatiles among beer aroma compounds was acetaldehyde, n-propanol, 3-methyl-butanol, 2-methyl-butanol, ethyl acetate, isoamyl acetate, 2,3-butanedione, and 2,3-pentanedione. It was ascertained that the total amount of higher alcohols was higher in the S. cerevisiae control beer compared to all mixed fermentations. Total ester levels were higher in all the mixed culture beers than the control beer. Sensory evaluation showed that all the mixed cultures of S. cerevisiae and T. delbrueckii positively influenced the sensory profile of the beers. Strain Y1031 was the most preferred and was characterized as rich in hop aroma and full bodied. It is therefore a suitable strategy to use T. delbrueckii in mixed fermentations with S. cerevisiae to produce beer with a distinctive flavor. The results demonstrate that, T. delbrueckii strains isolated or commercialized for winemaking can be equally employed as well in brewing.

Screening of Saccharomyces cerevisiae and Torulaspora delbrueckii strains in relation to their effect on malolactic fermentation.

The use of Torulaspora delbrueckii in the alcoholic fermentation (AF) of grape must is increasingly studied and used in the wine industry. In addition to the organoleptic improvement of wines, the synergy of this yeast species with the lactic acid bacterium Oenococcus oeni is an interesting field of study. In this work, 60 strain combinations were compared: 3 strains of Saccharomyces cerevisiae (Sc) and 4 strains of Torulaspora delbrueckii (Td) in sequential AF, and four strains of O. oeni (Oo) in malolactic fermentation (MLF). The objective was to describe the positive or negative relationships of these strains with the aim of finding the combination that ensures better MLF performance. In addition, a new synthetic grape must has been developed that allows the success of AF and subsequent MLF. Under these conditions, the Sc-K1 strain would be unsuitable for carrying out MLF unless there is prior inoculation with Td-Prelude, Td-Viniferm or Td-Zymaflore always with the Oo-VP41 combination. However, from all the trials performed, it appears that the combinations of sequential AF with Td-Prelude and Sc-QA23 or Sc-CLOS, followed by MLF with Oo-VP41, reflected a positive effect of T. delbrueckii compared to inoculation of Sc alone, such as a reduction in L-malic consumption time. In conclusion, the obtained results highlight the relevance of strain selection and yeast-LAB strain compatibility in wine fermentations. The study also reveals the positive effect on MLF of some T. delbrueckii strains.

Identification of genes related to hydrolysis and assimilation of Agave fructans in Candida apicola NRRL Y-50540 and Torulaspora delbrueckii NRRL Y-50541 by denovo transcriptome analysis.

Fructans are the main sugar in agave pine used by yeasts during mezcal fermentation processes, from which Candida apicola NRRL Y-50540 and Torulaspora delbrueckii NRRL Y-50541 were isolated. De novo transcriptome analysis was carried out to identify genes involved in the hydrolysis and assimilation of Agave fructans (AF). We identified a transcript annotated as SUC2, which is related to ß-fructofuranosidase activity, and several differential expressed genes involved in the transcriptional regulation of SUC2 such as: MIG1, MTH1, SNF1, SNF5, REG1, SSN6, SIP1, SIP2, SIP5, GPR1, RAS2, and PKA. Some of these genes were specifically expressed in some of the yeasts according to their fructans assimilation metabolism. Different hexose transporters that could be related to the assimilation of fructose and glucose were found in both the transcriptomes. Our findings provide a better understanding of AF assimilation in these yeasts and provide resources for further metabolic engineering and biotechnology applications.

Impact of Saccharomyces cerevisiae and non-Saccharomyces yeasts to improve traditional sparkling wines production.

In this study the effect of a co-inoculum of S. cerevisiae (F6789) with Torulaspora delbrueckii (TB1) or Starmerella bacillaris (SB48) on the oenological and aroma characteristics of sparkling wines obtained with the Champenoise method was investigated. The autolytic outcome and the sensory profile of sparkling wines were also evaluated. The secondary fermentations were completed by all mixed and single starter cultures with the only exception of those guided by Starm.bacillaris. Sparkling wines produced with S. cerevisiae F6789+Starm.bacillaris SB48 showed the highest amounts of glycerol (6.51 g/L). The best autolytic potential was observed in sparkling wines produced with +Starm.bacillaris (81.98 mg leucin/L) and S. cerevisiae+T. delbrueckii (79.03 mg leucin/L). The lowest value was observed for sparkling wines obtained with S. cerevisiae F6789 (53.96 mg leucin/L). Sparkling wines showed different aroma and sensory profiles. Esters were mainly present in sparkling wines obtained with S. cerevisiae F6789 (88.09 mg/L) followed by those obtained with S. cerevisiae+T. delbrueckii (87.20 mg/L), S. cerevisiae +Starm.bacillaris (81.93 mg/L). The content of esters decreased over time, and that might be related to the adsorption on lees and chemical hydrolysis. The highest concentrations of higher alcohols were found in sparkling wines produced with S. cerevisiae+T. delbrueckii (27.50 mg/L). Sparkling wines obtained with S. cerevisiae +Starm.bacillaris were well differentiated from the others due to their high score for the descriptor for spicy, bread crust, freshness and floral. Tailored strains with different autolytic potential might represent an interesting strategy to improve traditional sparkling wine production and favour their differentiation.

Genome Features of a New Double-Stranded RNA Helper Virus (LBCbarr) from Wine Torulaspora delbrueckii Killer Strains.

The killer phenotype of Torulaspora delbrueckii (Td) and Saccharomyces cerevisiae (Sc) is encoded in the genome of medium-size dsRNA viruses (V-M). Killer strains also contain a helper large size (4.6 kb) dsRNA virus (V-LA) which is required for maintenance and replication of V-M. Another large-size (4.6 kb) dsRNA virus (V-LBC), without known helper activity to date, may join V-LA and V-M in the same yeast. T. delbrueckii Kbarr1 killer strain contains the killer virus Mbarr1 in addition to two L viruses, TdV-LAbarr1 and TdV-LBCbarr1. In contrast, the T. delbrueckii Kbarr2 killer strain contains two M killer viruses (Mbarr1 and M1) and a LBC virus (TdV-LBCbarr2), which has helper capability to maintain both M viruses. The genomes of TdV-LBCbarr1 and TdV-LBCbarr2 were characterized by high-throughput sequencing (HTS). Both RNA genomes share sequence identity and similar organization with their ScV-LBC counterparts. They contain all conserved motifs required for translation, packaging, and replication of viral RNA. Their Gag-Pol amino-acid sequences also contain the features required for cap-snatching and RNA polymerase activity. However, some of these motifs and features are similar to those of LA viruses, which may explain that at least TdV-LBCbarr2 has a helper ability to maintain M killer viruses. Newly sequenced ScV-LBC genomes contained the same motifs and features previously found in LBC viruses, with the same genome location and secondary structure. Sequence comparison showed that LBC viruses belong to two clusters related to each species of yeast. No evidence for associated co-evolution of specific LBC with specific M virus was found. The presence of the same M1 virus in S. cerevisiae and T. delbrueckii raises the possibility of cross-species transmission of M viruses.

Hexose transport in Torulaspora delbrueckii: identification of Igt1, a new dual-affinity transporter.

Torulaspora delbrueckii is a yeast species receiving increasing attention from the biotechnology industry, with particular relevance in the wine, beer and baking sectors. However, little is known about its sugar transporters and sugar transport capacity, frequently a rate-limiting step of sugar metabolism and efficient fermentation. Actually, only one glucose transporter, Lgt1, has been characterized so far. Here we report the identification and characterization of a second glucose transporter gene, IGT1, located in a cluster, upstream of LGT1 and downstream of two other putative hexose transporters. Functional characterization of IGT1 in a Saccharomyces cerevisiae hxt-null strain revealed that it encodes a transporter able to mediate uptake of glucose, fructose and mannose and established that its affinity, as measured by Km, could be modulated by glucose concentration in the medium. In fact, IGT1-transformed S. cerevisiae hxt-null cells, grown in 0.1% glucose displayed biphasic glucose uptake kinetics with an intermediate- (Km = 6.5 ± 2.0 mM) and a high-affinity (Km = 0.10 ± 0.01 mM) component, whereas cells grown in 2% glucose displayed monophasic kinetics with an intermediate-affinity (Km of 11.5 ± 1.5 mM). This work contributes to a better characterization of glucose transport in T. delbrueckii, with relevant implications for its exploitation in the food industry.

Early adaptation strategies of Saccharomyces cerevisiae and Torulaspora delbrueckii to co-inoculation in high sugar grape must-like media.

Torulaspora delbrueckii and Saccharomyces cerevisiae are yeast species found concurrently in wine. In order to commence fermentation, they adapt to the initial harsh environment, maintaining cellular homeostasis and promoting metabolism. These actions involve an intricate regulation of stress tolerance, growth and metabolic genes. Their phenotypes are influenced by the fermentation environment and physiological state of the cell, but such gene-environment interactions are poorly understood. This study aimed to compare the cell physiology of the two species, through genome-wide analysis of gene expression, coupling Oxford Nanopore MinION and Illumina Hiseq sequencing platforms. The early transcriptional responses to stress, nutrients and cell-to-cell communication were analysed. Particular attention was given to the fundamental gene modulations, leading to an understanding of the physiological changes needed to maintain cellular homeostasis, exit the quiescent state and establish dominance in the fermentation. Our findings suggest the existence of species-specific adaptation strategies in response to growth in a high sugar synthetic grape juice medium.

Melatonin and glycolytic protein interactions are related to yeast fermentative capacity.

Melatonin is an indole amine that interacts with some proteins in mammals, such as calreticulin, calmodulin or sirtuins. In yeast, melatonin is synthetized and interacts with glycolytic proteins during alcoholic fermentation in Saccharomyces cerevisiae. Due to its importance as an antioxidant molecule in both Saccharomyces and non-Saccharomyces yeasts, the aim of this study was to determine the intracellular and extracellular synthesis profiles of melatonin in four non-Saccharomyces strains (Torulaspora delbrueckii, Hanseniaspora uvarum, Starmeralla bacillaris and Metschnikowia pulcherrima) and to confirm whether glycolytic enzymes can also interact with this molecule in non-conventional yeast cells. Melatonin from fermentation samples was analyzed by liquid chromatography mass spectrometry, and proteins bound to melatonin were immunopurified by melatonin-IgG-Dynabeads. Melatonin was produced in a similar pattern in all non-Saccharomyces yeast, with M. pulcherrima and S. bacillaris being the highest producers. However, melatonin only bound to proteins in two non-conventional yeasts, S. bacillaris and T. delbrueckii, which specifically had higher fermentative capacities. Sequence analysis showed that most proteins shared high levels of homology with glycolytic enzymes, but an RNA-binding protein, the elongation alpha factor, which is related to mitochondria, was also identified. This study reports for the first time the interaction of melatonin with proteins inside non-Saccharomyces yeast cells. These results reinforce the possible role of melatonin as a signal molecule, likely related to fermentation metabolism and provide a new perspective for understanding its role in yeast.

Nitrogen sources preferences of non-Saccharomyces yeasts to sustain growth and fermentation under winemaking conditions.

Wine-related non-Saccharomyces yeasts are becoming more widely used in oenological practice for their ability to confer wine a more complex satisfying aroma, but their metabolism remains unknown. Our study explored the nitrogen utilisation profile of three popular non-Saccharomyces species, Torulaspora delbrueckii, Metschnikowia pulcherrima and Metschnikowia fructicola. The nitrogen source preferences to support growth and fermentation as well as the uptake order of different nitrogen sources during wine fermentation were investigated. While T. delbrueckii and S. cerevisiae strains shared the same nitrogen source preferences, Metschnikowia sp. Displayed a lower capacity to efficiently use the preferred nitrogen compounds, but were able to assimilate a wider range of amino acids. During alcoholic fermentation, the non-Saccharomyces strains consumed different nitrogen sources in a similar order as S. cerevisiae, but not as quickly. Furthermore, when all the nitrogen sources were supplied in the same amount, their assimilation order was similarly affected for both S. cerevisiae and non-Saccharomyces strains. Under this condition, the rate of nitrogen source consumption of non-Saccharomyces strains and S. cerevisiae was comparable. Overall, this study expands our understanding about the preferences and consumption rates of individual nitrogen sources by the investigated non-Saccharomyces yeasts in a wine environment. This knowledge provides useful information for a more efficient exploitation of non-Saccharomyces strains that improves the management of the wine fermentation.

Volatile composition of bilberry wines fermented with non-Saccharomyces and Saccharomyces yeasts in pure, sequential and simultaneous inoculations.

Bilberry (Vaccinium myrtillus L.) juice was fermented with Torulaspora delbrueckii (TD291 and TD70526) and Schizosaccharomyces pombe (SP3796 and SP70572) in pure fermentation as well as in sequential and simultaneous inoculations with Saccharomyces cerevisiae 1116 (SC1116). Altogether, 56 volatile compounds were identified and semi-quantified with HS-SPME-GC/MS in bilberry products. Yeast fermentation prominently enhanced the aroma complexity of bilberry with a sharp increase in alcohols, esters, aldehydes, and acetals. Compared to S. cerevisiae, T. delbrueckii produced less ethanol but more fusel alcohols that potentially enhance "alcohol" and "nail polish" odors in TD70526 and less "fruity" esters in TD291. SP70572 resulted in high productions of undesirable compounds of acetoin and acetaldehyde but a low content of higher alcohols and esters, SP3796 produced a high content of fatty acid ethyl esters and acetoin. In comparison with monoculture of non-Saccharomyces yeast, sequential and simultaneous cultures of S. pombe and S. cerevisiae significantly decreased the content of acetoin while increased the relative level of esters; sequential cultures of T. delbrueckii and S. cerevisiae remarkably increased the concentration of acetaldehyde; simultaneous inoculations of S. cerevisiae with TD70526 and TD291 significantly decreased the content of fusel alcohols and increased the content of esters, respectively. The findings suggested that non-Saccharomyces yeasts possess the potential to affect and modulate the aromatic profile of fermented bilberry products. Sequential and simultaneous inoculations with S. pombe strains and S. cerevisiae as well as simultaneous fermentation using T. delbrueckii strains and S. cerevisiae are optimal strategies to positively influence the aroma profile of bilberry wines.

A Metagenomic-Based Approach for the Characterization of Bacterial Diversity Associated with Spontaneous Malolactic Fermentations in Wine.

This study reports the first application of a next generation sequencing (NGS) analysis. The analysis was designed to monitor the effect of the management of microbial resources associated with alcoholic fermentation on spontaneous malolactic consortium. Together with the analysis of 16S rRNA genes from the metagenome, we monitored the principal parameters linked to MLF (e.g., malic and lactic acid concentration, pH). We encompass seven dissimilar concrete practices to manage microorganisms associated with alcoholic fermentation: Un-inoculated must (UM), pied-de-cuve (PdC), Saccharomyces cerevisiae (SC), S. cerevisiae and Torulaspora delbrueckii co-inoculated and sequentially inoculated, as well as S. cerevisiae and Metschnikowia pulcherrima co-inoculated and sequentially inoculated. Surprisingly, each experimental modes led to different taxonomic composition of the bacterial communities of the malolactic consortia, in terms of prokaryotic phyla and genera. Our findings indicated that, uncontrolled AF (UM, PdC) led to heterogeneous consortia associated with MLF (with a relevant presence of the genera Acetobacter and Gluconobacter), when compared with controlled AF (SC) (showing a clear dominance of the genus Oenococcus). Effectively, the SC trial malic acid was completely degraded in about two weeks after the end of AF, while, on the contrary, malic acid decarboxylation remained uncomplete after 7 weeks in the case of UM and PdC. In addition, for the first time, we demonstrated that both (i) the inoculation of different non-Saccharomyces (T. delbrueckii and M. pulcherrima) and, (ii) the inoculation time of the non-Saccharomyces with respect to S. cerevisiae resources (co-inoculated and sequentially inoculated) influence the composition of the connected MLF consortia, modulating MLF performance. Finally, we demonstrated the first findings of delayed and inhibited MLF when M. pulcherrima, and T. delbrueckii were inoculated, respectively. In addition, as a further control test, we also assessed the effect of the inoculation with Oenococcus oeni and Lactobacillus plantarum at the end of alcoholic fermentation, as MLF starter cultures. Our study suggests the potential interest in the application of NGS analysis, to monitor the effect of alcoholic fermentation on the spontaneous malolactic consortium, in relation to wine.

Artisanal cachaça and brewer's spent grain as sources of yeasts with promising biotechnological properties.

AIMS: This study aimed to characterize yeasts isolated from the environment of artisanal cachaça production and brewer's spent grain-bearing in mind their further application in bioprocesses. METHODS AND RESULTS: Cell morphology, growth and fermentative parameters, and karyotyping were employed for the selection and grouping of yeast strains. The results showed that from 134 yeast strains studied, 14·2% exhibited cells with snowflake morphology, which is not appropriate for bioethanol production. The fermentation in sugarcane syrup was carried out with 71 Saccharomyces cerevisiae, 19 Torulaspora delbrueckii, eight Wickerhamomyces anomalus, six Candida parapsilosis, five Pichia mashurica, three Candida intermedia, two Clavispora lusitaniae and one Candida aaseri. Among the most important ethanol-producing strains, T. delbrueckii LMQA BSG 7 and S. cerevisiae LMQA SNR 65 presented biomass yield, ethanol yield and productivity similar or higher than PE-2 and CAT-1 (bioethanol industrial strains). CONCLUSIONS: This study showed a high potential for industrial application of the strains LMQA SNR 65 (S. cerevisiae) and LMQA BSG 7 (T. delbrueckii). It was found that the use of the chromosomal profile is not adequate to qualify yeasts concerning their technological performance. SIGNIFICANCE AND IMPACT OF THE STUDY: This study reported yeasts isolated from uncommon sources that present significant characteristics for potential application in bioprocesses.

Wine aromatic compound production and fermentative behaviour within different non-Saccharomyces species and clones.

AIMS: Twenty-five enological yeasts belonging to nine different species (Candida zeylanoides, Cryptococcus uzbekistanensis, Debaryomyces hansenii, Lachancea thermotolerans, Metschnikowia pulcherrima, Torulaspora delbrueckii, Williopsis pratensis, Zygosaccharomyces bailii and Saccharomyces cerevisiae) were screened for aroma formation and fermentative behaviour as part of a non-Saccharomyces yeast selection programme. METHODS AND RESULTS: Pure cultures were inoculated in pasteurized grape juice in order to perform alcoholic fermentations. Some non-Saccharomyces species did not ferment, others did not get established and none of them completed alcoholic fermentations. The physico-chemical parameters of the wines and the abundance of aromatic compounds at the end of alcoholic fermentation highlighted the notable differences in the aroma-forming ability and fermentative behaviour of the different non-Saccharomyces species, but not within clones. CONCLUSIONS: Lower diversity was detected within non-Saccharomyces species than that reported in S. cerevisiae with regard to enological behaviour and aromatic profiles. Metschnikowia pulcherrima and L. thermotolerans are the two species with higher possibilities to become an inoculum. SIGNIFICANCE AND IMPACT OF THE STUDY: Few significant differences were found within clones of the same species, but very important parameters in wine quality, such as volatile acidity, ethyl acetate and acetoin, which would justify selection programmes within those species. The results also demonstrated that T. delbrueckii and L. thermotolerans are two close species in their aromatic profiles.

The impact of Torulaspora delbrueckii yeast in winemaking.

Commercial Saccharomyces strains are usually inoculated to ferment alcoholic beverages due to their ability to convert all fermentable sugars into ethanol. However, modern trends in winemaking have turned toward less known, non-Saccharomyces yeast species. These species perform the first stages of natural spontaneous fermentation and play important roles in wine variety. New alcoholic fermentation trends have begun to consider objectives other than alcohol production to improve flavor diversity. This review explores the influence of the most used and commercialized non-Saccharomyces yeast, Torulaspora delbrueckii, on fermentation quality parameters, such as ethanol, glycerol, volatile acidity, volatile profile, succinic acid, mannoproteins, polysaccharides, color, anthocyanins, amino acids, and sensory perception.

Torulaspora delbrueckii for secondary fermentation in sparkling wine production.

In the search for the desired oenological features and flavour complexity of wines, there is growing interest in the potential use of non-Saccharomyces yeast that are naturally present in the winemaking environment. Torulaspora delbrueckii is one such yeast that has seen profitable use in mixed fermentations with Saccharomyces cerevisiae and with different grape varieties. T. delbrueckii can have positive and distinctive impacts on the overall aroma of wines, and has also been used at an industrial level. Here, T. delbrueckii was successfully used in pure and mixed secondary fermentations for sparkling wine. The two selected T. delbrueckii strains used completed the secondary fermentation 'prise de mousse' in these pure and mixed fermentations. The sparkling wines obtained with T. delbrueckii showed different aromatic compositions and sensory profiles to those of S. cerevisiae. T. delbrueckii strain DiSVA 130 showed high esters production and significantly high scores for some of the aromatic descriptors that positively influence the sensory profile of sparkling wine. Thus, the use of T. delbrueckii in pure and mixed fermentations is a suitable strategy to further develop the flavour complexity during secondary fermentation of sparkling wines.