Starmerella bacillaris and Saccharomyces cerevisiae mixed fermentations to reduce ethanol content in wine

Microbial Communities and Correlation between Microbiota and Volatile Compounds in Fermentation Starters of Chinese Sweet Rice Wine from Different Regions

Chinese sweet rice wines (CSRW) are traditional, regionally distinct alcoholic beverages that are generally brewed with glutinous rice and fermentation starters. This study aimed to characterize microbial communities and volatile compounds of CSRW starters and explore correlations between them. The major volatiles in starters include 1-heptanol, 1-octanol, 2-nonanol, phenylethyl alcohol, 2-nonanone, acetophenone, and benzaldehyde. Microbiological analysis based on high-throughput sequencing (HTS) technology demonstrated that starter bacterial communities are dominated by Weissella, Pediococcus, and Lactobacillus, while Saccharomycopsis and Rhizopus predominate in fungal communities. Carbohydrate and amino acid metabolism are the most active metabolic pathways in starters. Spearman correlation analysis revealed that 15 important volatile compounds including alcohols, acids, aldehydes and esters were significantly positively correlated with nine microbial genera (|r| > 0.7, p < 0.05), including five bacterial genera (i.e., Weissella, Pediococcus, Lactobacillus, Bacillus, and Nocardiopsis) and four fungal genera (i.e., Saccharomycopsis, Rhizopus, Wickerhamomyces, and Cyberlindnera), spanning 19 distinct relationships and these microorganisms were considered the core functional microorganisms in CSRW starters. The most important positive correlations detected between phenylethyl alcohol and Weissella or Saccharomycopsis and between 2-nonanol and Pediococcus. This study can serve as a reference to guide the development of defined starter cultures for improving the aromatic quality of CSRW.

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.

Oenological characteristics of two indigenous Starmerella bacillaris strains isolated from Chinese wine regions

To broaden knowledge about the oenological characteristics of Starmerella bacillaris, the influence of two Chinese indigenous S. bacillaris strains on the conventional enological parameters and volatile compounds of Cabernet Sauvignon wines were investigated under different inoculation protocols (single inoculation and simultaneous/sequential inoculation with the commercial Saccharomyces cerevisiae EC1118). The results showed that the two S. bacillaris strains could complete alcohol fermentation alone under high sugar concentrations while increasing the content of glycerol and decreasing the content of acetic acid. Compared with wines fermented by EC1118 single inoculation, S. bacillaris single inoculation and S. bacillaris/EC1118 sequential inoculation increased the contents of isobutanol, ethyl isobutanoate, terpenes, and ketones and decreased the contents of isopentanol, phenylethyl alcohol, fatty acids, acetate esters, and total ethyl esters. Furthermore, for S. bacillaris/EC1118 simultaneous inoculation, the concentrations of ethyl esters were increased, contributing to a higher score of "floral" and "fruity" notes in agreement with sensory analysis. KEY POINTS: • S. bacillaris single and simultaneous/sequential inoculation. • Conventional enological parameters and volatile compounds were investigated. • S. bacillaris/EC1118 simultaneous fermentation increased ethyl esters.

Characterization of Nero Antico di Pretalucente Wine and Grape Fungal Microbiota: An Expression of Abruzzo Region Cultivar Heritage

The aim of this study was to characterize the ampelographic and genetic profiles of Vitis vinifera L. cv. Nero Antico di Pretalucente and to describe the grape-borne fungal communities. The oenological characteristics and the aroma profile of wine obtained by spontaneous fermentation were also investigated. Microsatellite profiles and ampelographic traits indicated that this cultivar presented a unique profile, and therefore it can be considered a cultivar in its own right and autochthonous of Gessopalena village. Next-generation sequencing analysis revealed that Aureobasidium spp. was the main genus detected on grapes. At the species level, Aureobasidium pullulans was the main species, followed by Alternaria alternata. Wines were characterized by a final ethanol content of 12.75% (v/v), a pH of 3.4, a volatile acidity lower than 0.6 g/L, a content of glycerol of 8.56 g/L, and a concentration of polyphenols and anthocyanins of 977 GAE/L and 266 mg/L, respectively. The intensity and tonality of the wine as well as the active odor compounds found were described. The results obtained could improve the knowledge concerning the agronomic traits and the wine obtained from this ancient and autochthonous grapevine variety cultivated in a foothill area, in order to offer consumers a wine with unique traits.

Starmerella bacillaris Released in Vineyards at Different Concentrations Influences Wine Glycerol Content Depending on the Vinification Protocols

Starmerella bacillaris is a non-Saccharomyces yeast proposed for must fermentation together with Saccharomyces cerevisiae because of its high glycerol and moderate volatile acidity production. Furthermore, it was demonstrated that the same S. bacillaris strains that possess interesting technological properties exhibited antifungal activity against Botrytis cinerea, suggesting the release of this yeast in the vineyard. To obtain a positive effect during the following winemaking process, the maintenance of suitable concentrations of S. bacillaris is essential. Therefore, to obtain information on the survival of S. bacillaris, a small-scale field trial was performed. One week before the harvest, two different concentrations of S. bacillaris (10⁶ and 10⁷ cells/mL) were sprayed on Pinot grigio bunches, and the strain concentration was monitored by means of qPCR during the subsequent fermentation process. In addition, the combined effect of different winemaking techniques was evaluated, i.e., the vinification of juice, juice with marc and cryomaceration treatment. Results demonstrated that, under the tested conditions, S. bacillaris released in the vineyard remained viable for one week on grape bunches and increased glycerol content during the subsequent fermentation process. Different vinification protocols influenced cell concentrations. In particular, the cryomaceration treatment, due to the use of low temperature, supported S. bacillaris growth due to its cryotolerant aptitude. The collected data open new perspectives on the control of alcoholic fermentation, involving both vineyard and cellar management.

Application of Cool Fermentation Temperatures to Encourage Non-Saccharomyces Yeasts to Yield Lower Ethanol Concentrations in Wines

Application of cool temperatures were studied to encourage Metschnikowia pulcherrima P01A016 and Meyerozyma guilliermondii P40D002 prior inoculation of Saccharomyces cerevisiae D254 to lower ultimate ethanol concentrations achieved. Merlot grape must was distributed into 300 L temperature-controlled tanks and inoculated with non-Saccharomyces yeasts three days before S. cerevisiae. For control fermentations, S. cerevisiae was inoculated with maximum temperatures set to 25 °C (temperature regime I) while those with Mt. pulcherrima or My. guilliermondii were initially set to 15 °C (temperature regime II) or 17.5 °C (temperature regime III) before increasing to 25 °C after adding S. cerevisiae. Once fermentations achieved dryness (≤2 g/L residual sugar), wines were bottled and stored for six months at 7 °C before sensory analysis. Ethanol reduction by Mt. pulcherrima was not observed in wines fermented under II but was by III (0.8% v/v). In contrast, musts inoculated with My. guilliermondii yielded wines with ethanol concentrations lowered by 0.3% (II) or 0.4% v/v (III). Sensory panelists found wines with Mt. pulcherrima to express lower sensory scores for ‘hotness’, ‘bitterness’, and ‘ethanol’ flavor with fewer differences noted for My. guilliermondii. Reducing final ethanol concentrations of Merlot wines were achieved by Mt. pulcherrima or My. guilliermondii using cooler initial fermentation temperatures without adversely affecting final wine quality.

Prospection of indigenous yeasts from Uruguayan Tannat vineyards for oenological applications

Prospection of yeasts from oenological environments can provide knowledge of new native strains that are capable of fermenting must and positively influence the composition and sensory characteristics of the wine. This work addressed the biotechnological characterization of indigenous yeasts of Tannat must, an emblematic and widespread vineyard of Uruguay. Fifty-three yeast isolates were morphologically characterized and further identified by amplification and sequencing of ITS and D1-D2 regions, grouping into a total of fifteen species. One isolate of each species was randomly chosen and evaluated for its technological traits. In presence of ethanol (6 to 16% v/v) and sulfur dioxide (40 mg/L), native Saccharomyces cerevisiae 3FS presented the best growth rates and minor lag phase. Regarding non-Saccharomyces strains, Starmerella bacillaris 3MS stood out for its behavior in vinification conditions, more closely related to S. cerevisiae strains. Saccharomyces cerevisiae 3FS, Starmerella bacillaris 3MS, and Saturnispora diversa 1FS conducted a successful fermentation process reaching a final ethanol concentration ≥ 10% v/v and presenting a killer and resistant phenotype, suggesting that they could be used as pure starter cultures, as well as in mixed culture fermentations. This preliminary screening and oenological characterization of indigenous Saccharomyces cerevisiae and non-Saccharomyces yeasts might be a useful tool to identify some strains as potential candidates for wine vinification.

Starmerella bacillaris Strains Used in Sequential Alcoholic Fermentation with Saccharomyces cerevisiae Improves Protein Stability in White Wines

Haze can appear in white wines as a result of the denaturation and subsequent aggregation of grape pathogenesis-related (PR) proteins. Yeast cell-wall polysaccharides, particularly mannoproteins, represent a promising strategy to reduce the incidence of this phenomenon. The aim of this study was to evaluate the effects of 13 Starmerella bacillaris strains, in sequential fermentation with Saccharomyces cerevisiae, on wine protein stability of three white wines (Sauvignon blanc, Pinot grigio, and Manzoni bianco). The resulting wines were characterized in terms of their chemical composition, content of PR proteins and polysaccharides, and heat stability. In addition, the mannoprotein fraction was purified from six wines, five produced with S. bacillaris and one with S. cerevisiae EC1118 used as control. Generally, wines produced with S. bacillaris strains were more heat-stable, despite generally containing higher amounts of PR proteins. The increased heat stability of Starmerella wines was attributed to the stabilizing effect resulting from their higher concentrations of both total polysaccharides and mannoprotein fractions. In particular, for the most heat unstable wine (Manzoni bianco), the low MW mannoprotein fraction resulted to be the most involved in wine stability. The ability to produce wines with different heat stability was demonstrated to be strain-dependent and was more evident in the most unstable wines. By reducing fining waste, the use of S. bacillaris as an enological starter can be proposed as a new tool to manage wine protein stability for a more sustainable winemaking.

Effect of Yeast Assimilable Nitrogen Content on Fermentation Kinetics, Wine Chemical Composition and Sensory Character in the Production of Assyrtiko Wines

Two wild-type Saccharomyces cerevisiae yeast strains (Sa and Sb) were tested for white wine production using Assyrtiko grape of Santorini. A third commercial Saccharomyces strain was also studied for comparison reasons. Two concentrations of yeast extract and diammonium phosphate (DAP) were added to the must (150 and 250 mg/L) in order to evaluate the effect of nitrogen content on the final wine quality. Analytical methods (HPLC, GC-MS) and sensory analysis were employed to assess the quality of the wines. Fermentation kinetics were monitored throughout the experiment. By the second day of fermentation, all strains showed an approximate consumption of 70% of amino acids. Differences among strains were observed regarding inorganic nitrogen requirements. Sb strain resulted in higher concentrations of higher alcohols (1.9-fold) and ketones (5.6-fold) and lower concentrations of esters (1.2-fold) compared to the control, while Sa strain resulted in higher content of fatty acids (2.1-fold). Both indigenous strains scored better results in aroma quality, body and acidity compared to control. The overall evaluation of the data highlights the great potential of the indigenous S. cerevisiae strains as fermentation starters providing promising results in the sector of terroir wines.

Promoting Candida zemplinina adhesion on oak chips: A strategy to enhance esters and glycerol content of Montepulciano d'Abruzzo organic wines

In this study cell surface hydrophobicity and the ability to adhere on abiotic surfaces (polystyrene plates, stainless steel and oak chips) of 10 Candida zemplinina strains were assessed. Moreover, the impact of C. zemplinina cells adhered on oak surface on fermentation kinetics and volatile profile of Montepulciano d'Abruzzo organic wines was evaluated. All strains showed a hydrophobic nature with a certain affinity for the apolar solvents tested (hexadecane and decane). In agreement with this data strains were able to adhere on abiotic surfaces in a strain dependent way. On polystyrene plates all strains mainly grew as planktonic cells. On stainless steel surfaces sessile cells ranged from 2.6 Log CFU/mL (SB2) to 4.1 Log CFU/mL (SB8), while on oak chips were about 2 log higher ranging from 4.3 Log CFU/mL (SB8) to 6.1 Log CFU/mL (SB10). Candida zemplinina sessile state resulted in an increase of glycerol (from 6.98 g/L to 11.92 g/L) and esters amount (from 55.47 g/L to 91.5 mg/L), and a reduction of ethanol content (from 14.13% to 9.12% v/v). As for esters, methyl vanillate, ethyl isobutyrate, and ethyl isovalerate were present only when C. zemplinina was adhered on oak chips. This study revealed that changes of concentrations in esters and glycerol content reflected the fermentation bioactivity of yeast cells attached on oak chips. Surface-adhered behaviours should be considered in the improvement of strategies for the development of high-quality organic wines and eventually obtain novel wine styles.

Biotechnological Approaches to Lowering the Ethanol Yield during Wine Fermentation

One of the most prominent consequences of global climate warming for the wine industry is a clear increase of the sugar content in grapes, and thus the alcohol level in wines. Among the several approaches to address this important issue, this review focuses on biotechnological solutions, mostly relying on the selection and improvement of wine yeast strains for reduced ethanol yields. Other possibilities are also presented. Researchers are resorting to both S. cerevisiae and alternative wine yeast species for the lowering of alcohol yields. In addition to the use of selected strains under more or less standard fermentation conditions, aerobic fermentation is increasingly being explored for this purpose. Genetic improvement is also playing a role in the development of biotechnological tools to counter the increase in the wine alcohol levels. The use of recombinant wine yeasts is restricted to research, but its contribution to the advancement of the field is still relevant. Furthermore, genetic improvement by non-GMO approaches is providing some interesting results, and will probably result in the development of commercial yeast strains with a lower alcohol yield in the near future. The optimization of fermentation processes using natural isolates is, anyway, the most probable source of advancement in the short term for the production of wines with lower alcohol contents.

Techniques for Dealcoholization of Wines: Their Impact on Wine Phenolic Composition, Volatile Composition, and Sensory Characteristics

The attention of some winemakers and researchers over the past years has been drawn towards the partial or total dealcoholization of wines and alcoholic beverages due to trends in wine styles, and the effect of climate change on wine alcohol content. To achieve this, different techniques have been used at the various stages of winemaking, among which the physical dealcoholization techniques, particularly membrane separation (nanofiltration, reverse osmosis, evaporative perstraction, and pervaporation) and thermal distillation (vacuum distillation and spinning cone column), have shown promising results and hence are being used for commercial production. However, the removal of alcohol by these techniques can cause changes in color and losses of desirable volatile aroma compounds, which can subsequently affect the sensory quality and acceptability of the wine by consumers. Aside from the removal of ethanol, other factors such as the ethanol concentration, the kind of alcohol removal technique, the retention properties of the wine non-volatile matrix, and the chemical-physical properties of the aroma compounds can influence changes in the wine sensory quality during dealcoholization. This review highlights and summarizes some of the techniques for wine dealcoholization and their impact on wine quality to help winemakers in choosing the best technique to limit adverse effects in dealcoholized wines and to help meet the needs and acceptance among different targeted consumers such as younger people, pregnant women, drivers, and teetotalers.

Evaluation of Autochthonous Non-Saccharomyces Yeasts by Sequential Fermentation for Wine Differentiation in Galicia (NW Spain)

Non-Saccharomyces yeasts constitute a useful tool in winemaking because they secrete hydrolytic enzymes and produce metabolites that enhance wine quality; in addition, their ability to reduce alcohol content and/or to increase acidity can help to mitigate the effects of climatic change on wines. The purpose of this study was to evaluate the oenological traits of non-Saccharomyces yeast strains autochthonous from Galicia (NW Spain). To do that, we carried out sequential fermentation using 13 different species from the yeast collection of Estación de Viticultura e Enoloxía de Galicia (Evega) and Saccharomyces cerevisiae EC1118. The fermentation kinetics and yeast implantation were monitored using conventional methods and genetic techniques, respectively. The basic chemical parameters of wine were determined using the OIV official methodology, and the fermentative aroma compounds were determined by GC–FID. The results evidenced the limited fermentative power of these yeasts and the differences in their survival after the addition of S. cerevisiae to complete fermentation. Some strains reduced the alcohol and/or increased the total acidity of the wine. The positive effect on sensory wine properties as well as the production of desirable volatile compounds were confirmed for Metschnikowia spp. (Mf278 and Mp176), Lachancea thermotolerans Lt93, and Pichia kluyveri Pkl88. These strains could be used for wine diversification in Galicia.

Chemical and Sensory Profiles of Merlot Wines Produced by Sequential Inoculation of Metschnikowia pulcherrima or Meyerzyma guilliermondii

Inoculation of selected non-Saccharomyces yeasts with Saccharomyces cerevisiae as means to produce Merlot wines with reduced ethanol contents was investigated. Fermentations of grape musts (25.4° Brix, pH 3.50, and 4.23 g/L titratable acidity) were conducted in stainless steel tanks inoculated with Metschnikowia pulcherrima strains P01A016 or NS-MP or Meyerozyma guilliermondii P40D002 with S. cerevisiae Syrah added after three days. After fermentation, wines with Mt. pulcherrima contained 13.8% (P01A016) or 13.9% (NS-MP) v/v ethanol, respectively, amounts which were lower than in wines with S. cerevisiae alone (14.9% v/v). Delayed inoculation of must with S. cerevisiae (day 3) or musts with My. guilliermondii contained elevated concentrations of ethyl acetate (145 and 148 mg/L, respectively), concentrations significantly higher than those with S. cerevisiae inoculated on day 0 or with either strain of Mt. pulcherrima. Descriptive sensory analysis revealed a significant effect due to panelist but not due to Mt. pulcherrima or My. guilliermondii. This research indicates the potential for commercial application of these yeasts towards the production of reduced alcohol wines but without imparting negative sensory attributes.

Yeast Interactions and Molecular Mechanisms in Wine Fermentation: A Comprehensive Review

Wine can be defined as a complex microbial ecosystem, where different microorganisms interact in the function of different biotic and abiotic factors. During natural fermentation, the effect of unpredictable interactions between microorganisms and environmental factors leads to the establishment of a complex and stable microbiota that will define the kinetics of the process and the final product. Controlled multistarter fermentation represents a microbial approach to achieve the dual purpose of having a less risky process and a distinctive final product. Indeed, the interactions evolved between microbial consortium members strongly modulate the final sensorial properties of the wine. Therefore, in well-managed mixed fermentations, the knowledge of molecular mechanisms on the basis of yeast interactions, in a well-defined ecological niche, becomes fundamental to control the winemaking process, representing a tool to achieve such objectives. In the present work, the recent development on the molecular and metabolic interactions between non-Saccharomyces and Saccharomyces yeasts in wine fermentation was reviewed. A particular focus will be reserved on molecular studies regarding the role of nutrients, the production of the main byproducts and volatile compounds, ethanol reduction, and antagonistic actions for biological control in mixed fermentations.

Influence of Microencapsulation on Fermentative Behavior of Hanseniaspora osmophila in Wine Mixed Starter Fermentation

In recent years, as a consequence of the re-evaluation of the role of non-Saccharomyces yeasts, several studies have been conducted on the use of controlled mixed fermentations with Saccharomyces and different non-Saccharomyces yeast species from the winemaking environment. To benefit from the metabolic particularities of some non-Saccharomyces yeasts, the management of a non-Saccharomyces strain in mixed fermentation is a crucial step, in particular the use of procedures addressed to increase the persistence of non-Saccharomyces strains during the fermentative process. The use of microencapsulation for cell immobilization might represent a strategy for enhancing the competitiveness of non-Saccharomyces yeasts during mixed fermentation. This study was aimed to assess the fermentative performance of a mixed starter culture, composed by a wild Hanseniaspora osmophila strain (ND1) and a commercial Saccharomyces cerevisiae strain (EC1118). For this purpose, free and microencapsulated cells of ND1 strain were tested in co-culture with EC1118 during mixed fermentations in order to evaluate the effect of the microencapsulation on fermentative behavior of mixed starter and final wine composition. The data have shown that H. osmophila cell formulation affects the persistence of both ND1 and EC1118 strains during fermentations and microencapsulation resulted in a suitable system to increase the fermentative efficiency of ND1 strain during mixed starter fermentation.

Genetic, Physiological, and Industrial Aspects of the Fructophilic Non-Saccharomyces Yeast Species, Starmerella bacillaris

Starmerella bacillaris (synonym Candida zemplinina) is a non-Saccharomyces yeast species, frequently found in enological ecosystems. Peculiar aspects of the genetics and metabolism of this yeast species, as well as potential industrial applications of isolated indigenous S. bacillaris strains worldwide, have recently been explored. In this review, we summarize relevant observations from studies conducted on standard laboratory and indigenous isolated S. bacillaris strains.

Starmerella bombicola and Saccharomyces cerevisiae in Wine Sequential Fermentation in Aeration Condition: Evaluation of Ethanol Reduction and Analytical Profile

In the last few decades, the increase of ethanol in wine, due to global climate change and consumers’ choice is one of the main concerns in winemaking. One of the most promising approaches in reducing the ethanol content in wine is the use of non-Saccharomyces yeasts in co-fermentation or sequential fermentation with Saccharomyces cerevisiae. In this work, we evaluate the use of Starmerella bombicola and S. cerevisiae in sequential fermentation under aeration condition with the aim of reducing the ethanol content with valuable analytical profile. After a preliminary screening in synthetic grape juice, bench-top fermentation trials were conducted in natural grape juice by evaluating the aeration condition (20 mL/L/min during the first 72 h) on ethanol reduction and on the analytical profile of wines. The results showed that S. bombicola/S. cerevisiae sequential fermentation under aeration condition determined an ethanol reduction of 1.46% (v/v) compared with S. cerevisiae pure fermentation. Aeration condition did not negatively affect the analytical profile of sequential fermentation S. bombicola/S. cerevisiae particularly an overproduction of volatile acidity and ethyl acetate. On the other hand, these conditions strongly improved the production of glycerol and succinic acid that positively affect the structure and body of wine.

Effect of a Multistarter Yeast Inoculum on Ethanol Reduction and Population Dynamics in Wine Fermentation

Microbiological strategies are currently being considered as methods for reducing the ethanol content of wine. Fermentations started with a multistarter of three non-Saccharomyces yeasts (Metschnikowia pulcherrima (Mp), Torulaspora delbrueckii (Td) and Zygosaccharomyces bailii (Zb)) at different inoculum concentrations. S. cerevisiae (Sc) was inoculated into fermentations at 0 h (coinoculation), 48 h or 72 h (sequential fermentations). The microbial populations were analyzed by a culture-dependent approach (Wallerstein Laboratory Nutrient (WLN) culture medium) and a culture-independent method (PMA-qPCR). The results showed that among these three non-Saccharomyces yeasts, Td became the dominant non-Saccharomyces yeast in all fermentations, and Mp was the minority yeast. Sc was able to grow in all fermentations where it was involved, being the dominant yeast at the end of fermentation. We obtained a significant ethanol reduction of 0.48 to 0.77% (v/v) in sequential fermentations, with increased concentrations of lactic and acetic acids. The highest reduction was achieved when the inoculum concentration of non-Saccharomyces yeast was 10 times higher (10⁷ cells/mL) than that of S. cerevisiae. However, this reduction was lower than that obtained when these strains were used as single non-Saccharomyces species in the starter, indicating that interactions between them affected their performance. Therefore, more combinations of yeast species should be tested to achieve greater ethanol reductions.

Impacts of non-Saccharomyces species and aeration on sequential inoculation with Saccharomyces cerevisiae to produce lower alcohol Merlot wines from Washington state

BACKGROUND

Species of non-Saccharomyces yeasts isolated from Washington vineyards were evaluated for their abilities to reduce alcohol contents of wines. As many of these yeasts benefit from some oxygen, the effect of limited aeration was also studied.

RESULTS

Although fermentations of a high sugar Merlot grape must (310 g L^-1 ) did not reach dryness, inoculation of Metschnikowia chrysoperlae, Mt. pulcherrima, Meyerozyma guillermondii, Pichia kluyveri, or P. membranifaciens yielded in wines with lower amounts of ethanol without excessive levels of acetic acid. Aeration frequently resulted in wines with less ethanol but with more acetic acid compared to non-aerated fermentations. Inoculation of Mt. pulcherrima or My. guilliermondii into another Merlot grape must that contained a lower initial amount of fermentable sugar (266 g L^-1 ) resulted in dry wines that contained less alcohol.

CONCLUSIONS

Inoculation of My. guilliermondii or Mt. pulcherrima before primary alcoholic fermentation resulted in wines with reduced alcohol contents without excessive acetic acid production. © 2020 Society of Chemical Industry.

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.

Correlation between bacterial community succession and propionic acid during gray sufu fermentation

In order to explore the correlation between the production of propionic acid (PA) and the succession of bacterial community during the fermentation of gray sufu, high-throughput sequencing and HPLC (High Performance Liquid Chromatography) were used to monitor the changes of bacterial community and metabolite content. The abundance and metabolite concentration of Propionibacterium increased rapidly in the early stage of fermentation. In the middle stage, the abundance of Lactobacillus began to increase, while the pH decreased rapidly. In the late stage, the concentration of PA began to decrease, but it remained at a high level at the end of fermentation. Correlation analysis showed that Lactobacillus and Bacillus had a strong negative correlation with PA and its precursor. The results showed that Fusobacterium, Providencia, Lactobacillus and Bacillus could be the key factors to reduce the PA content. This study provides a new idea for the quality control of traditional fermented food.

Color Stabilization of Apulian Red Wines through the Sequential Inoculation of Starmerella bacillaris and Saccharomyces cerevisiae

Mixed fermentation using Starmerella bacillaris and Saccharomyces cerevisiae has gained attention in recent years due to their ability to modulate the qualitative parameters of enological interest, such as the color intensity and stability of wine. In this study, three of the most important red Apulian varieties were fermented through two pure inoculations of Saccharomyces cerevisiae strains or the sequential inoculation of Saccharomyces cerevisiae after 48 h from Starmerella bacillaris. The evolution of anthocyanin profiles and chromatic characteristics were determined in the produced wines at draining off and after 18 months of bottle aging in order to assess the impact of the different fermentation protocols on the potential color stabilization and shelf-life. The chemical composition analysis showed titratable acidity and ethanol content exhibiting marked differences among wines after fermentation and aging. The 48 h inoculation delay produced wines with higher values of color intensity and color stability. This was ascribed to the increased presence of compounds, such as stable A-type vitisins and reddish/violet ethylidene-bridge flavonol-anthocyanin adducts, in the mixed fermentation. Our results proved that the sequential fermentation of Starmerella bacillaris and Saccharomyces cerevisiae could enhance the chromatic profile as well as the stability of the red wines, thus improving their organoleptic quality.

Influence of Non-Saccharomyces on Wine Chemistry: A Focus on Aroma-Related Compounds

Wine fermentation processes are driven by complex microbial systems, which comprise eukaryotic and prokaryotic microorganisms that participate in several biochemical interactions with the must and wine chemicals and modulate the organoleptic properties of wine. Among these, yeasts play a fundamental role, since they carry out the alcoholic fermentation (AF), converting sugars to ethanol and CO₂ together with a wide range of volatile organic compounds. The contribution of Saccharomyces cerevisiae, the reference organism associated with AF, has been extensively studied. However, in the last decade, selected non-Saccharomyces strains received considerable commercial and oenological interest due to their specific pro-technological aptitudes and the positive influence on sensory quality. This review aims to highlight the inter-specific variability within the heterogeneous class of non-Saccharomyces in terms of synthesis and release of volatile organic compounds during controlled AF in wine. In particular, we reported findings on the presence of model non-Saccharomyces organisms, including Torulaspora delbrueckii, Hanseniaspora spp,Lachancea thermotolerans, Metschnikowia pulcherrima, Pichia spp. and Candida zemplinina, in combination with S. cerevisiae. The evidence is discussed from both basic and applicative scientific perspective. In particular, the oenological significance in different kind of wines has been underlined.

From the vineyard to the cellar: new insights of Starmerella bacillaris (synonym Candida zemplinina) technological properties and genomic perspective

A large diversity of yeasts can be involved in alcoholic fermentation; however, Starmerella bacillaris strains have gained great attention due to their relevant and particular characteristics. S. bacillaris is commonly known as an osmotolerant, acidogenic, psychrotolerant, and fructophilic yeast. Most strains of this species are high producers of glycerol and show low ethanol production rates, being highlighted as promising alternatives to the manufacture of low-alcohol beverages. The increased production of high alcohols, such as benzyl alcohol that has antifungal and antibacterial properties, highlights S. bacillaris potential as a biocontrol agent. After harvest, antifungal yeasts become part of the must microbiota and may also improve the fermentation process. Moreover, during the fermentation, S. bacillaris releases important molecules with biotechnological properties, such as mannoproteins and glutathione. Considering the potential biotechnological properties of S. bacillaris strains, this review presents an overview of recent trends concerning the application of S. bacillaris in fermented beverages. KEY POINTS: •S. bacillaris as an alternative to the production of low-alcohol beverages. •S. bacillaris strains present biocontrol potential. •Molecules released by S. bacillaris may be of great biotechnological interest.

Determination of the microbial communities of Guizhou Suantang, a traditional Chinese fermented sour soup, and correlation between the identified microorganisms and volatile compounds

Guizhou Suantang (GZST), a type of sour soup, is a traditional fermented food that can be classified into Hong Suantang (HST) and Bai Suantang (BST). GZST possesses unique flavors arising from various microbiota in fermentation ecosystems. However, the association between these microbiota and flavors remains poorly understood. Accordingly, this study analyzed the volatile components and microbial communities of GZST via headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry and high-throughput 16S rRNA and internal transcribed spacer sequencing techniques. Results showed that 133 compounds, including alcohols, esters, phenols, hydrocarbons, ketones, aldehydes, nitriles, acids, and sulfides, were identified from GZST. Moreover, principal component analysis found significant variances in the composition of volatile compounds among different samples. The bacterial genus level indicated that all GZST samples were dominated by Lactobacillus. At the fungal genus level, BST was dominated by Pichia, Debaryomyces, Mortierella, unclassified, Meyerozyma, and Dipodascus. Meanwhile, HST was dominated by Pichia, Candida, Kazachstania, Debaryomyces, Archaeorhizomyces, and Verticillium. The potential correlations between microbiota and volatile components were also explored through bidirectional orthogonal partial least squares-based correlation analysis. Nine bacterial genera and eight fungal taxa were identified as functional core microbiota for flavor production on the basis of their dominance and functionality in the microbial community. In addition, excessive Lactobacillus inhibited the formation of certain flavor substances. These findings provided basic data for the isolation, screening, and fermentation regulation of functional microorganisms in GZST. The information provided in this study is valuable for the development of effective strategies for selecting beneficial bacterial and fungal strains to improve the quality of GZST.

The Effect of Non-Saccharomyces and Saccharomyces Non-Cerevisiae Yeasts on Ethanol and Glycerol Levels in Wine

Non-Saccharomyces and Saccharomyces non-cerevisiae studies have increased in recent years due to an interest in uninoculated fermentations, consumer preferences, wine technology, and the effect of climate change on the chemical composition of grapes, juice, and wine. The use of these yeasts to reduce alcohol levels in wines has garnered the attention of researchers and winemakers alike. This review critically analyses recent studies concerning the impact of non-Saccharomyces and Saccharomyces non-cerevisiae on two important parameters in wine: ethanol and glycerol. The influence they have in sequential, co-fermentations, and solo fermentations on ethanol and glycerol content is examined. This review highlights the need for further studies concerning inoculum rates, aeration techniques (amount and flow rate), and the length of time before Saccharomyces cerevisiae sequential inoculation occurs. Challenges include the application of such sequential inoculations in commercial wineries during harvest time.

Temperature-Induced Annual Variation in Microbial Community Changes and Resulting Metabolome Shifts in a Controlled Fermentation System

We are rapidly increasing our understanding on the spatial distribution of microbial communities. However, microbial functioning, as well as temporal differences and mechanisms causing microbial community shifts, remains comparably little explored. Here, using Chinese liquor fermentation as a model system containing a low microbial diversity, we studied temporal changes in microbial community structure and functioning. For that, we used high-throughput sequencing to analyze the composition of bacteria and fungi and analyzed the microbially derived metabolome throughout the fermentation process in all four seasons in both 2018 and 2019. We show that microbial communities and the metabolome changed throughout the fermentation process in each of the four seasons, with metabolome diversity increasing throughout the fermentation process. Across seasons, bacterial and fungal communities as well as the metabolome driven by 10 indicator microorganisms and six metabolites varied even more. Daily average temperature in the external surroundings was the primary determinant of the observed temporal microbial community and metabolome changes. Collectively, our work reveals critical insights into patterns and processes determining temporal changes of microbial community composition and functioning. We highlight the importance of linking taxonomic to functional changes in microbial ecology to enable predictions of human-relevant applications.IMPORTANCE We used Chinese liquor fermentation as a model system to show that microbiome composition changes more dramatically across seasons than throughout the fermentation process within seasons. These changes translate to differences in the metabolome as the ultimate functional outcome of microbial activity, suggesting that temporal changes in microbiome composition are translating into functional changes. This result is striking as it suggests that microbial functioning, despite controlled conditions in the fermentors, fluctuates over season along with external temperature differences, which threatens a reproducible food taste. As such, we believe that our study provides a stepping-stone into novel taxonomy-functional studies that promote future work in other systems and that also is relevant in applied settings to better control surrounding conditions in food production.

Pilot Scale Fermentations of Sangiovese: An Overview on the Impact of Saccharomyces and Non-Saccharomyces Wine Yeasts

The production of wines with peculiar analytical and sensorial profiles, together with the microbiological control of the winemaking process, has always been one of the main objectives of the wine industry. In this perspective, the use of oenological starters containing non-Saccharomyces yeasts can represent a valid tool for achieving these objectives. Here we present the results of seven pilot scale fermentations, each of which was inoculated with a different non-Saccharomyces yeast strain and after three days with a commercial Saccharomyces cerevisiae starter. The fermentations were carried out in double on 70 L of Sangiovese grape must, the most widely planted red grape variety in Italy and particularly in Tuscany, where it is utilized for the production of more than 80% of red wines. Fermentations were monitored by assessing both the development of the microbial population and the consumption of sugars at the different sampling times. The impact of the different starters was assessed after stabilization through the evaluation of the standard analytical composition of the resulting wines, also taking into account polysaccharides and volatile compounds. Moreover, quantitative descriptive sensory analyses were carried out. Compared to the control wines obtained by inoculating the S. cerevisiae starter strain, those inoculated with non-Saccharomyces/Saccharomyces mixed starters presented a significant differentiation in the chemical-analytical composition. Moreover, sensory analysis revealed differences among wines mainly for intensity of color, astringency, and dryness mouthfeel perception.

Oenological potential of non-Saccharomyces yeasts to mitigate effects of climate change in winemaking: impact on aroma and sensory profiles of Treixadura wines

The effects of climate change on wine include high-alcohol content, low acidity and aroma imbalance. The potential of several non-Saccharomyces wine yeasts to mitigate these effects was evaluated by sequential fermentation of Treixadura grape must. Fermentations with only Saccharomyces cerevisiae ScXG3 and a spontaneous process were used as control assays. All yeast strains were obtained from the yeast collection of Estación de Viticultura e Enoloxía de Galicia (EVEGA), Galicia, Spain. Fermentation kinetics as well as yeast dynamics and implantation ability varied depending on inoculated yeasts. In addition, the results showed significant differences in the chemical composition of wine. Starmerella bacillaris 474 reduced the alcohol content (1.1% vol) and increased the total acidity (1.2 g L-1) and glycerol of wines. Fermentation with Lachancea thermotolerans Lt93 and Torulaspora delbrueckii Td315 also decreased the alcohol content, although to a lesser extent (0.3% and 0.7% vol, respectively); however, their effect on wine acidity was less significant. The wines also differed in their concentration of volatile compounds and sensory characteristics. Thus, wines made with Metschnikowia fructicola Mf278 and S. cerevisiae ScXG3 had higher content of esters, acetates and some acids than other wines, and were most appreciated by tasters due to their fruity character and overall impression.

The microbial challenge of winemaking: yeast-bacteria compatibility

The diversity and complexity of wine environments present challenges for predicting success of fermentation. In particular, compatibility between yeast and lactic acid bacteria is affected by chemical and physical parameters that are strain and cultivar specific. This review focuses on the impact of compound production by microbes and physical interactions between microbes that ultimately influence how yeast and bacteria may work together during fermentation. This review also highlights the importance of understanding microbial interactions for yeast-bacteria compatibility in the wine context.

Effect of Co-Inoculation of Candida zemplinina, Saccharomyces cerevisiae and Lactobacillus plantarum for the Industrial Production of Negroamaro Wine in Apulia (Southern Italy)

The employment of multi-species starter cultures has growing importance in modern winemaking for improving the complexity and wine attributes. The assessment of compatibility for selected species/strains at the industrial-scale is crucial to assure the quality and the safety associated with fermentations. An aspect particularly relevant when the species belong to non-Saccharomyces, Saccharomyces spp. and malolactic bacteria, three categories with different biological characteristics and oenological significance. To the best of our knowledge, the present report is the first study regarding the utilization of a combined starter culture composed of three strains of non-Saccharomyces, Saccharomyces cerevisiae and Lactobacillus plantarum for production of wine at the industrial scale. More in-depth, this work investigated the oenological potential of the autochthonous characterized strains from the Apulian region (Southern Italy), Candida zemplinina (syn. Starmerella bacillaris) 35NC1, S. cerevisiae (NP103), and L. plantarum (LP44), in co-inoculation following a complete scale-up scheme. Microbial dynamics, fermentative profiles and production of volatile secondary compounds were assessed in lab-scale micro-vinification tests and then the performances of the mixed starter formulation were further evaluated by pilot-scale wine production. The above results were finally validated by performing an industrial-scale vinification on 100HL of Negroamaro cultivar grape must. The multi-starter formulation was able to rule the different stages of the fermentation processes effectively, and the different microbial combinations enhanced the organoleptic wine features to different extents. The findings indicated that the simultaneous inoculation of the three species affect the quality and quantity of several volatile compounds, confirming that the complexity of the wine can reflect the complexity of the starter cultures. Moreover, the results underlined that the same mixed culture could differently influence wine quality when tested at the lab-, pilot- and industrial-scale. Finally, we highlighted the significance of employment non-Saccharomyces and L. plantarum, together with S. cerevisiae, autochthonous strains in the design of custom-made starter culture formulation for typical regional wine production with pronounced unique quality.

Effects of High Sugar Content on Fermentation Dynamics and Some Metabolites of Wine-Related Yeast Species Saccharomyces cerevisiae, S. uvarum and Starmerella bacillaris

Starmerella bacillaris (synonym Candida zemplinina) is an important non-Saccharomyces yeast in winemaking with valuable oenological properties, accompanying Saccharomyces species in sweet wine fermentation, and has been suggested also for application as combined starter culture in dry or sweet wines. In this study, the major metabolites and nitrogen utilization of these yeasts are evaluated in the musts with high or extremely high sugar concentration. The change in the metabolic footprint of Saccharomyces cerevisiae, Saccharomyces uvarum and Starmerella bacillaris strains was compared when they were present as pure cultures in chemically defined grape juice medium with 220 and 320 g/L of sugar, to represent a fully matured and an overripe grape. Surprisingly, the extreme sugar concentration did not result in a considerable change in the rate of sugar consumption; only a shift of the sugar consumption curves could be noticed for all species, especially for Starmerella bacillaris. At the extreme sugar concentration, Starmerella bacillaris showed excellent glycerol production, moderate nitrogen demand together with a noticeable proline utilisation. The change in the overall metabolite pattern of Starmerella bacillaris allowed clear discrimination from the change of the Saccharomyces species. In this experiment, the adequacy of this non-Saccharomyces yeast for co-fermentation in juices with high sugar concentration is highlighted. Moreover, the results suggest that Starmerella bacillaris has a more active adaptation mechanism to extremely high sugar concentration.

A Rapid Method for Selecting Non-Saccharomyces Strains with a Low Ethanol Yield

The alcohol content in wine has increased due to external factors in recent decades. In recent reports, some non-Saccharomyces yeast species have been confirmed to reduce ethanol during the alcoholic fermentation process. Thus, an efficient screening of non-Saccharomyces yeasts with low ethanol yield is required due to the broad diversity of these yeasts. In this study, we proposed a rapid method for selecting strains with a low ethanol yield from forty-five non-Saccharomyces yeasts belonging to eighteen species. Single fermentations were carried out for this rapid selection. Then, sequential fermentations in synthetic and natural must were conducted with the selected strains to confirm their capacity to reduce ethanol compared with that of Saccharomyces cerevisiae. The results showed that ten non-Saccharomyces strains were able to reduce the ethanol content, namely, Hanseniaspora uvarum (2), Issatchenkia terricola (1), Metschnikowia pulcherrima (2), Lachancea thermotolerans (1), Saccharomycodes ludwigii (1), Torulaspora delbrueckii (2), and Zygosaccharomyces bailii (1). Compared with S. cerevisiae, the ethanol reduction of the selected strains ranged from 0.29 to 1.39% (v/v). Sequential inoculations of M. pulcherrima (Mp51 and Mp FA) and S. cerevisiae reduced the highest concentration of ethanol by 1.17 to 1.39% (v/v) in synthetic or natural must. Second, sequential fermentations with Z. bailii (Zb43) and T. delbrueckii (Td Pt) performed in natural must yielded ethanol reductions of 1.02 and 0.84% (v/v), respectively.

New Insights into the Oenological Significance of Candida zemplinina: Impact of Selected Autochthonous Strains on the Volatile Profile of Apulian Wines

In this investigation, we explored the oenological significance of Candida zemplinina (syn. Starmerella bacillaris) isolates from Apulian grape musts. Moreover, we provide the first evidence of the impact of different C. zemplinina strains on the wine aromatic properties tested as monocultures. We described the diversity of C. zemplinina strains isolated from grapes and the variability of 'volatile' phenotypes associated with this intraspecific variability. Thirty-three isolates were characterized at strain level by PCR-based approach and, among these, 16 strains were identified and then tested by microfermentation tests carried out in grape must. Analyzed strains were low producers of acetic acid and hydrogen sulphide, not able to decarboxylate a panel of representative amino acids, whereas they showed fructophilic character and significant glycerol production. Volatile profiles of produced wines were investigated by gas chromatography-mass spectrometry. The Odor Activity Values of all molecules were calculated and 12 compounds showed values above their odor thresholds. Two selected strains (35NC1 and 15PR1) could be considered as possible starter cultures since they were able to positively affect the sensory properties of obtained wine. This report firstly supplies evidence on the strain-specific impact of different C. zemplinina strains on the final aroma of produced wines.

Effect of mixed fermentations with Starmerella bacillaris and Saccharomyces cerevisiae on management of malolactic fermentation

This work aims to improve the management of the malolactic fermentation (MLF) in red wines by elucidating the interactions between Starmerella bacillaris and Saccharomyces cerevisiae in mixed fermentations and malolactic bacteria. Two Starm. bacillaris strains were individually used in mixed fermentations with a commercial S. cerevisiae. MLF was performed using two autochthonous Lactobacillus plantarum and one commercial Oenococcus oeni inoculated following a simultaneous (together with S. cerevisiae) or sequential (at the end of alcoholic fermentation) approach. The impact of yeast inoculation on the progress of MLF was investigated by monitoring the viable microbial populations and the evolution of the main oenological parameters, as well as the volatile organic composition of the wines obtained in mixed and pure micro-scale winemaking trials. Our results indicated that MLF was stimulated, inhibited, or unaffected in mixed fermentations depending on the strains and on the regime of inoculation. O. oeni was able to perform MLF under all experimental conditions, and it showed a minimal impact on the volatile organic compounds of the wine. L. plantarum was unable to perform MLF in sequential inoculation assays, and strain-depending interactions with Starm. bacillaris were indicated as factor affecting the outcome of MLF. Moreover, uncompleted MLF were related to a lower aromatic complexity of the wines. Our evidences indicate that tailored studies are needed to define the appropriate management of non-Saccharomyces and malolactic starter cultures in order to optimize some technological parameters (i.e. reduction of vinification time) and to improve qualitative features (i.e. primary and secondary metabolites production) of red wines.

Nitrogen Preferences during Alcoholic Fermentation of Different Non-Saccharomyces Yeasts of Oenological Interest

Non-Saccharomyces yeasts have long been considered spoilage microorganisms. Currently, oenological interest in those species is increasing, mostly due to their positive contribution to wine quality. In this work, the fermentative capacity and nitrogen consumption of several non-Saccharomyces wine yeast (Torulaspora delbrueckii, Lachancea thermotolerans, Starmerella bacillaris, Hanseniaspora uvarum, and Metschnikowia pulcherrima) were analyzed. For this purpose, synthetic must with three different nitrogen compositions was used: a mixture of amino acids and ammonium, only organic or inorganic nitrogen. The fermentation kinetics, nitrogen consumption, and yeast growth were measured over time. Our results showed that the good fermentative strains, T. delbrueckii and L. thermotolerans, had high similarities with Saccharomyces cerevisiae in terms of growth, fermentation profile, and nitrogen assimilation preferences, although L. thermotolerans presented an impaired behavior when only amino acids or ammonia were used, being strain-specific. M. pulcherrima was the non-Saccharomyces strain least affected by the nitrogen composition of the medium. The other two poor fermentative strains, H. uvarum and S. bacillaris, behaved similarly regarding amino acid uptake, which occurred earlier than that of the good fermentative species in the absence of ammonia. The results obtained in single non-Saccharomyces fermentations highlighted the importance of controlling nitrogen requirements of the wine yeasts, mainly in sequential fermentations, in order to manage a proper nitrogen supplementation, when needed.

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.

Advances in yeast alcoholic fermentations for the production of bioethanol, beer and wine

Yeasts have a long-standing relationship with humankind that has widened in recent years to encompass production of diverse foods, beverages, fuels and medicines. Here, key advances in the field of yeast fermentation applied to alcohol production, which represents the predominant product of industrial biotechnology, will be presented. More specifically, we have selected industries focused in producing bioethanol, beer and wine. In these bioprocesses, yeasts from the genus Saccharomyces are still the main players, with Saccharomyces cerevisiae recognized as the preeminent industrial ethanologen. However, the growing demand for new products has opened the door to diverse yeasts, including non-Saccharomyces strains. Furthermore, the development of synthetic media that successfully simulate industrial fermentation medium will be discussed along with a general overview of yeast fermentation modeling.

Effect of mixed species alcoholic fermentation on growth and malolactic activity of lactic acid bacteria

In recent years, there is an increasing interest from the winemaking industry for the use of mixed fermentations with Starmerella bacillaris (synonym Candida zemplinina) and Saccharomyces cerevisiae, due to their ability to modulate metabolites of oenological interest. The current study was carried out to elucidate the effect of this fermentation protocol on the growth and malolactic activity of lactic acid bacteria (LAB) used for malolactic fermentation (MLF) and on the chemical and volatile profile of Nebbiolo wines and their chromatic characteristics. To this end, two LAB species, namely Lactobacillus plantarum and Oenococcus oeni, were inoculated at the beginning and at the end of the alcoholic fermentation (AF) performed by pure and mixed yeast using the abovementioned yeasts. The different yeast inoculation protocols and the combination of species tested influenced greatly the interactions and behavior of the inoculated yeasts and LAB during AF and MLF. For both LAB species, inoculation timing was critical to how rapidly MLF started and finished. Fermentation inoculated with L. plantarum, at the beginning of the AF, completed MLF faster than those inoculated with O. oeni. The presence of Starm. bacillaris in mixed fermentation promoted LAB growth and activity, in particular, O. oeni. Furthermore, LAB species choice had a greater impact on the volatile and chromatic profile of the wines than inoculation time. These findings reveal new knowledge about the importance of LAB species choice and inoculation time to ensure fast MLF completion and to improve wine characteristics in mixed fermentation with Starm. bacillaris and S. cerevisiae.