Abstract Yeasts are widely recognized for their industrial and fermentative relevance, but their potential as source of antibacterial compounds remains significantly underexplored compared to bacteria or filamentous fungi. This study evaluated a wide taxonomically characterized population of yeast strains for their antimicrobial activity against enteropathogenic bacteria, plant pathogens and spoilage molds, using both direct-contact and VOC-mediated assays. Our findings reveal that antimicrobial activity, including the production of inhibitory VOCs, is highly complex, depending not only on the genus and species but also on unique traits at the strain level. Metschnikowia pulcherrima exhibited a broad inhibitory spectrum against both molds and bacteria, driven by non-volatile, multifactorial mechanisms such as iron chelation and antimicrobial metabolites. In contrast, Hanseniaspora and Wickerhamomyces displayed more versatile behaviour, combining strong antifungal properties with VOC-mediated antibacterial activity. Aureobasidium and Meyerozyma genera showed a functional specialization toward antifungal activity, with limited or no effect on bacterial pathogens. The specific strains of B. bruxellensis evaluated in this study emerged as notable producers of bioactive VOCs under the tested in vitro conditions. While these results highlight a significant antagonistic potential, the observed activity appears to be strain-specific. This underscores the importance of intra-specific screening to identify ‘elite’ isolates with superior biocontrol traits, rather than assuming a uniform species-level metabolic profile. Key points • Yeasts antimicrobial activity is genus/species relevant strain-specific traits. • Several yeast genera showed inhibitory activity against enteropathogenic bacteria. • B. bruxellensis represents a promising source of bioactive VOCs against both bacteria and mold.

The craft beer market is continually expanding, driven by the consumers’ demand for product diversification, which leads to innovation in the brewing industry. While traditional brewing focuses on consistency and high-volume efficiency using standard yeasts, craft brewing prioritizes small-batch experimentation and flavor complexity. Traditionally, Saccharomyces cerevisiae (Ale beer) and Saccharomyces pastorianus (Lager beer) yeast are used in brewing. The craft brewing revolution introduced the use of non-conventional yeast. These yeasts possess distinct technological characteristics compared to commercial starters, such as a richer enzyme profile. This biological diversity produces beers with novel, complex aroma profiles, and opens exciting avenues for flavor creation. Recently, non-alcoholic beer and low-alcoholic beer (NABLAB), and functional beer have become the new horizons for the application of non-conventional yeasts. In recent years, the brewing potential of these alternative yeasts has been extensively explored. However, some aspects relating to the interactions between yeast and raw materials precursors involved in the aroma of the final beer, and the management of yeasts in fermentation, remain unexplored. This review systematically outlines the various innovative ways in which non-conventional yeasts are applied in brewing, including healthier beer. Here, we explore how these yeasts can foster innovation in the beer sector and provide the possibility for sustainable development in contemporary brewing.

Kombucha is a reservoir of health-promoting yeast strains. In this study, molecular characterization of the Kombucha microbiota led to the identification of 52 distinct yeast isolates, highlighting a complex community, where Brettanomyces anomalus was identified as the dominant yeast species. Other key species were identified, such as Pichia membranifaciens, Torulaspora delbrueckii, Zygosaccharomyces bailii, Starmerella bacillaris, and Meyerozyma guilliermondii. These isolated yeasts were screened for essential probiotic requirements, demonstrating excellent functional traits showing over 80% survival rate under simulated gastric and gastrointestinal conditions. Regarding the surface properties, wide cell hydrophobicity and auto-aggregation capabilities were seen. Broad antioxidant ability and robust antimicrobial activity against Escherichia coli and Staphylococcus aureus were observed, highlighting a protective function. Two strains of T. delbrueckii and one strain of Z. bailii stood out as probiotic candidates and were technologically evaluated in different culture combinations: yeast formulation pools using a specialized “probiotic pool” (PP) and a broader “yeast pool” (YP) both yielded successful analytical and sensory profiles. A strain of Lachancea thermotolerans, isolated from a distinct natural matrix, was employed as a technological booster to drive a yeast-based, bacteria-free kombucha. This study confirmed that specialized kombucha yeasts were not just fermentation drivers, but sustainable assets for developing novel functional plant-based probiotic beverages.

In recent years, there has been an increased interest in non-Saccharomyces yeasts for their use in the production of sparkling wines to obtain products with distinctive flavor and increased aromatic complexity. Despite this, there are few studies focused on understanding the effects of using non-Saccharomyces yeasts in the secondary fermentation of sparkling wine production. In this study, two strains of Lachancea thermotolerans selected for primary fermentation were evaluated in secondary fermentation ‘prise de mousse’ using two base wines from different vintages. The pressure-kinetic analysis showed that one strain of L. thermotolerans exhibited limited secondary fermentation aptitude, while the other exhibited secondary fermentation kinetics comparable to those of the Saccharomyces cerevisiae strain. The resulting sparkling wines, although presenting comparable main analytical characteristics, differed in aromatic composition and sensory profiles. Based on these characters, beyond the different base wines, the strains of L. thermotolerans showed a clear different contribution to the resulting sparkling wines. The influence of L. thermotolerans compared with S. cerevisiae it was found in the production of higher alcohols and acetate esters and appeared to be strictly dependent on the specific strain used and the chemical composition of base wine. L. thermotolerans DiSVA322 exhibited the best score in the sensory analysis of resulting sparkling wines, exhibiting, together with a relevant score for citrus and tropical fruit, a significantly high score for softness, structure, and aromatic herbs descriptors. Thus, the use of L. thermotolerans in secondary fermentation of sparkling wine could be a suitable strategy to enhance aroma profile and flavor complexity.

Bee bread is a fermented product derived from bee pollen, whose fermentation improves preservation, nutrient bioavailability, and functional properties. However, the microbial succession driving this process, particularly the role of yeasts, remains poorly understood. This study investigated microbial dynamics during fourteen-day spontaneous fermentation of five fresh bee pollen samples from different geographical origins, mimicking natural bee bread formation. Cultivable yeasts and lactic acid bacteria were monitored by viable cell counts and molecular identification. Physicochemical parameters, nutritional components, bioactivities, and pollen structure were evaluated. A clear microbial succession was observed, with Starmerella sp. dominating the early stages and the osmotolerant yeast Zygosaccharomyces rouxii prevailing during the final phase. Together with Apilactobacillus kunkeei, these microorganisms may constitute a cultivable fermentative core involved in bee bread formation. Fermentation significantly increased protein availability, with increases of up to 18%, reduced pH, promoted bee pollen degradation up to 16%, and enhanced antimicrobial activity against Staphylococcus aureus and Listeria monocytogenes. Understanding of cultivable microbiota dynamics during spontaneous bee pollen fermentation could provide an effective natural strategy to stabilize bee pollen while improving its nutritional and functional properties, laying the foundation for developing controlled industrial fermentations to produce bee bread-like products with consistent quality and health-promoting characteristics.

In recent years, consumer demand has been increasingly oriented to fermented foods and/or beverages with functional properties. The functional beverage industry focused on producing a product that combines a peculiar aromatic taste with healthy properties. Today’s consumers are trying to reduce alcohol, gluten, sugar, and carbohydrates in beer and wine without reducing their native taste. Wine and beer are among the world’s most consumed beverages, and several studies confirm that fermented beverages could be associated with beneficial properties for human health. All beneficial properties derive both from the fermentation process and also from the characteristics of the raw materials used in the two beverages. This review was conducted to highlight the importance of the fermentative microorganisms in wine and beer and their relationship with functional foods, underlining their involvement in human health.

Sparkling wine production involves secondary alcoholic fermentation, during which carbon dioxide is trapped, creating effervescence and enhancing sensory complexity. This study evaluated the impact of Torulaspora delbrueckii and Lachancea thermotolerans yeast species using free and immobilized cells in secondary fermentation of sparkling wine, in comparison with Saccharomyces cerevisiae. Immobilized S. cerevisiae enabled faster refermentation compared to free cells, while immobilization resulted in a slower process in non-Saccharomyces strains. Biomass monitoring showed stable viable cells for immobilized S. cerevisiae during fermentation, while non-Saccharomyces strains showed a consistent reduction. Volatile profiles were positively influenced by immobilization using S. cerevisiae strains, which produced a constant increase in key aroma compounds, such as geraniol and ethyl acetate, throughout fermentation. Non-Saccharomyces strains contributed to enhanced fruity and floral aromas with variations in volatiles during refermentation. Sparkling wines fermented with immobilized L. thermotolerans were noted for ripe fruit aromas, while T. delbrueckii increased floral notes. S. cerevisiae fermentations showed higher acidity and balanced structure. These findings highlight the influence of yeast species and the yeast immobilization procedures in secondary fermentation, modulating fermentation dynamics and aroma development, and offer a promising strategy to tailor sparkling wine quality and sensory complexity.

One of the most relevant challenges in winemaking is the increase in the alcohol content of wine, mainly due to climate change. The use of selected non-Saccharomyces yeasts in sequential fermentation with Saccharomyces cerevisiae is one of the effective strategies for dealing with this issue, even if it has been poorly confirmed at the winery level. This work evaluated the use of Starmerella bombicola and commercial S. cerevisiae strains in sequential fermentation at pilot scale in winery conditions to reduce the ethanol content and obtain a wine with enhanced aroma complexity. The results showed that the sequential S. bombicola/S. cerevisiae fermentation in aeration conditions (20 mL/L/min for the first three days) resulted in a reduction in ethanol of 0.80% (v/v) compared to pure S. cerevisiae fermentation. The aeration conditions of sequential fermentation did not affect the fermentation performance of yeasts. The winery conditions determined, in the sequential fermentation modalities, an enhancement of wild yeasts’ presence. At the same time, the inoculation of S. bombicola determined an enhancement of glycerol and lactic acid, which positively influences the structure and body of the wine as well as specific aromatic notes. In winery conditions, better control of fermentation is needed to achieve potential ethanol reduction and favorable by-product formation using S. bombicola.

Nowadays, yeasts are widely used for food and beverage fermentation as well as for their functional traits, as there has been an increase in scientific interest in their contributions to human health. Microbial competition in habitats with adverse abiotic factors could force yeasts to activate competitive tools, such as bioactive compound production. Here, bee pollen, fresh bee bread, and aged bee bread were analyzed as a reservoir of potential new functional yeasts. Microbiological analyses of pollen showed a dominance of bacteria and molds, although yeasts were present in all samples and increased in fresh and aged bee bread where osmophilic yeasts appeared. Functional traits such as antioxidant activity; polyphenol and flavonoid production; antimicrobial activity toward molds, yeast, and pathogenic bacteria; phytase activity; and potential probiotic aptitude were studied. Out of fifty-eight isolated yeasts, four showed antioxidant activity higher (around 70%) than Codex® due to having the highest levels of polyphenols or flavonoids. One strain possessed phytase activity, and three strains belonging to Starmerella and Metschnikowia genera had wide antimicrobial activity. Nine strains exhibited the ability to resist gastrointestinal conditions, and four possessed all probiotic traits tested. All these findings demonstrate the effectiveness of pollen and bee bread as natural sources for new bioactive and functional yeasts.

Non-alcoholic beer (NAB) and low-alcoholic beer (LAB) are taking over the market with growing sales. Sustainable recycling and valorization of exhausted brewer’s spent grain (BSG) coming from craft beer is a relevant issue in the brewing process. In this work, recycled BSG and BSG + GJ (supplemented with 10% grape juice) were used as a wort substrate to inoculate Lachancea thermotolerans, Wickeramhomyces anomalus, Torulaspora delbruecki and Pichia kluyveri non-conventional yeasts to produce NABLAB craft beer. Results showed that wort composed of only recycled BSG produced appreciated NAB beers (ethanol concentration from 0.12% to 0.54% v/v), while the addition of 10% grape juice produced LAB beers (ethanol concentration from 0.82 to 1.66% v/v). As expected, volatile compound production was highest with the addition of grape juice. L. thermotolerans showed lactic acid production, characterizing both worts with the production of ethyl butyrate and isoamyl acetate. T. delbrueckii exhibited relevant amounts of hexanol, phenyl ethyl acetate and β-phenyl ethanol (BSG + GJ). W. anomalus and P. kluyveri showed consistent volatile production, but only in BSG + GJ where fermentation activity was exhibited. The overall results indicated that reused BSGs, non-conventional yeasts and grape juice are suitable bioprocesses for specialty NABLAB beer.

The yeast Saccharomyces cerevisiae ensures successful fermentation in winemaking, although the persistent use of commercial strains lead to the loss of aroma complexity of wines. Hence, the research of indigenous S. cerevisiae with proper oenological features and well adapted to specific wine-growing areas become of great interest for winemakers. Here, 206 pure cultures of S. cerevisiae were isolated from two wineries during a two-year sampling campaign and bio-typed through interdelta sequences analyses with the aim to evaluate the occurrence and persistence of the S. cerevisiae wild population linked to each winery. Both wineries belong to the same Verdicchio DOC wine area (Castelli di Jesi), and never used commercial yeasts during fermentation. Results showed 19 different biotypes with a specific population of S. cerevisiae in each winery, without cross-contamination with each other and with commercial starter strains. Moreover, inside each winery a persistence of some dominant biotypes was observed over time (three biotypes in winery 1; 95% of isolates in the two years and one biotype in winery 2; 20% of isolates in the two years), indicating a sort of “winery-effect”. The evaluation of S. cerevisiae populations for the oenological characters by microfermentations showed a proper and well distinct aromatic imprinting on the resulted wines supporting the concept of “winery effect”.

Functional foods represent one of the fastest-growing, newer food category, and plant sources with functional properties are increasingly used as analogues of fermented milk-based derivatives. In this study, blended wortrooibos beverages fermented with probiotic yeasts are proposed for the first time. Benefits of functional, nonconventional Lachancea thermotolerans (Lt101), Kazachstania unispora (Kum3-B3), Meyerozyma guilliermondii (Mg112), Meyerozyma caribbica (Mc58) and Debaryomyces hansenii (Dh36) yeast strains and the content of bioactive metabolites were evaluated. Viability tests on the probiotic yeasts confirmed previous results obtained in other matrices. The functional footprint of probiotic yeasts Lt101, Mg112 and Dh36 was confirmed by a balanced nutritional profile of the final drinks, also supported by aromatic and sensory analyses. In vitro estimated glycaemic index ranged between 77 % and 87 % without any influence on glycaemic response. Strains Dh36, Mc58, Kum3-B3 and Mg112 showed high antioxidant capacity and high total phenolic content, supporting the health promoting effect of the beverages.

Brettanomyces yeasts play a relevant role in the fermentation industry, showing controversial behavior. There is growing interest in these yeasts in the fermentation industry as beer and bioethanol production, while in winemaking, they are considered spoilage microorganisms mainly used to produce ethyl phenols. These compounds may alter wine’s organoleptic characteristics, leading to significant economic loss. In this work, 45 Brettanomyces strains from seven different environments were genotyped and assayed for some oenological characters to investigate the possible relationship among sources of isolation, genotype characterization, and oenological characters. The results of biotyping showed four main clusters which were also distinguished according to the oenological characters. The oenological characters also distinguished the strains based on the isolation source, suggesting an overall relation between origin and biotypes. The negative correlation between fermentation rate and ethyl phenols production in the Brettanomyces population may indicate the adaptation to hostile environments differently from crop strains that showed the opposite behavior. The overall results contribute to clarifying some features of Brettanomyces yeasts, even if further investigations into the ability of these yeasts to colonize winemaking environments are needed.

Probiotic microorganisms are used to improve the health and wellness of people and the research on this topic is of current relevance and interest. Fifty-five yeasts, coming from honeybee's ecosystem and belonging to Candida, Debaryomyces, Hanseniaspora, Lachancea, Metschnikowia, Meyerozyma, Starmerella and Zygosacchromyces genera and related different species, were evaluated for the probiotic traits. The resistance to gastrointestinal conditions, auto-aggregation, cell surface hydrophobicity or biofilm formation abilities as well as antimicrobial activity against common human pathogenic bacteria were evaluated. The safety analysis of strains was also carried out to exclude any possible negative effect on the consumer's health. The influence of proteinase treatment of living yeasts and their adhesion to Caco-2 cells were also evaluated. The greatest selection occurred in the first step of survival at the acidic pH and in the presence of bile salts, where more than 50% of the strains were unable to survive. Equally discriminating was the protease test which allowed the survival of only 27 strains belonging to the species Hanseniaspora guilliermondii, Hanseniaspora uvarum, Metschnikowia pulcherrima, Metschnikowia ziziphicola, Meyerozyma caribbica, Meyerozyma guilliermondii, Pichia kluyveri, Pichia kudriavzevii and Pichia terricola. An integrated analysis of the results obtained allowed the detection of seven yeast strains with probiotic aptitudes, all belonging to the Meyerozyma genus, of which three belonging to M. guillermondii and four belonging to M. caribbica species.

(1) Background: in this study, bee pollen, fresh and aged beebread, collected in the central Italy during the spring/summer 2024, were analysed as reservoir of potential new probiotic yeast strains. (2) Methods: culture dependent methods and molecular analyses were used to quantify and identify bacteria, molds and yeasts populations (3) Results: microbiological analyses of pollen showed a clear dominance of molds and bacteria over yeasts in all samples. In mature beebread the presence of lactic acid or other bacterial metabolites preserved the development of molds that were almost absent. As a general abundance, yeasts were about ten times less than bacteria, in particular the osmophilic yeasts were more abundant in pollen. Specifically, four yeast genera were identified in bee pollen, Cryptococcus, Starmerella, Bullera, Microstroma and five in the beebread, Starmerella, Zygosaccharomyces, Metschnikowia, Aureobasidium, Kodamaea and Moniliella. (4) Conclusions: out of 58 assayed yeasts, 9 strains exhibited the ability to resist to gastrointestinal physicochemical condition and 4 possessed all probiotic traits tested, demonstrating the effectiveness of pollen and beebread as natural source for new bioactive and functional yeasts.

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

Torulaspora delbrueckii has attracted renewed interest in recent years, for its biotechnological potential linked to its ability to enhance the flavor and aroma complexity of wine. Sequential fermentations with a selected native strain of T. delbrueckii (DiSVA 130) and low-sulfite native strain of Saccharomyces cerevisiae (DiSVA 709) were carried out to establish their contribution in biocontrol and the aroma profile. A first set of trials were conducted to evaluate the effect of the sulfur dioxide addition on pure and T. debrueckii/S. cerevisiae sequential fermentations. A second set of sequential fermentations without SO2 addition were conducted to evaluate the biocontrol and aromatic effectiveness of T. delbrueckii. Native T. delbrueckii showed a biocontrol action in the first two days of fermentation (wild yeasts reduced by c.a. 1 log at the second day). Finally, trials with the combination of both native and commercial T. delbrueckii/S. cerevisiae led to distinctive aromatic profiles of wines, with a significant enhancement in isoamyl acetate, phenyl ethyl acetate, supported by positive appreciations from the tasters, for ripe and tropical fruits, citrus, and balance. The whole results indicate that native T. delbrueckii could be a potential biocontrol tool against wild yeasts in the first phase of fermentation, contributing to improving the final wine aroma.

The non-alcoholic beer sector has seen steady growth in recent years and non-conventional yeasts could be a chance to produce this specialty beer. On the other hand, non-alcoholic beer with appreciated aromatic characteristics remains a challenge. In this work, 14 yeast strains belonging to 7 different species were tested to produce low-alcohol or alcohol-free beers using recycled low-sugar wort from brewers spent grains (BSG). The results showed that a strain of Lachancea thermotolerans and a strain of Torulaspora delbrueckii exhibited a fermentation evolution comparable to that of Saccharomyces cerevisiae commercial strain with a reduced ethanol (0.46, 0.57, 1.22 % v/v respectively). L. thermotolerans strains were characterized by lactic acid production and esters formation with the strain DiSVA 322 that exhibited the best aromatic and sensorial performance. T. delbrueckii DiSVA 253 showed an effective analytical profile with a peculiar sensory profile. Although Pichia kluyveri strains did not show significant fermentation evolution, the strains DiSVA 1078 and DiSVA 1079 revealed positive sensorial and analytical traits that significantly distinguished the beers for fruity/esters and sweet notes. The wort from recycled BSG resulted a favourable substrate to produce of non-alcoholic or low alcoholic beers in conjunction with selected non-conventional yeasts.

One of the main objectives for a sustainable winemaking process is the reduction of the use of sulfur dioxide. In this regard, non-Saccharomyces wine yeasts are proposed as biocontrol agent in different steps of wine production chain. Here, a selected strain of Metschnikowia pulcherrima (DiSVA 269) and a native Saccharomyces cerevisiae low sulfite producer strain (DiSVA 708) were investigated. After preliminary laboratory trials, winemaking process at industrial level showed an effective biocontrol action (reduction of c.a. 1 Log order of wild yeasts) of M. pulcherrima inoculated at prefermentative stage in cold clarification (48 h at 10 degrees C) and during the subsequent fermentation process. The combination of M. pulcherrima/S. cerevisiae led a distinctive aromatic profile of wines both in laboratory and winery trials with a significant enhancement of ethyl butyrate, ethyl hexanoate, isoamyl acetate and 8-phenyl ethanol. Moreover the use of the two selected strains was the best combination to enhance volatile thiols (3-mercaptohexan-1-ol and 3-mercaptoexil acetate) that well correlate with the sensory analysis (tropical fruits). The overall results indicate that the combined use of M. pulcherrima DiSVA 269 and native S. cerevisiae DiSVA 708 led a biocontrol action and an improvement of aromatic and sensorial profile of wine with low SO2 content.