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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 wort-rooibos beverages fermented with probiotic yeasts are proposed for the first time. Benefits of functional, non-conventional 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.
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Antioxidantes , Fermentação , Alimentos Fermentados , Probióticos , Leveduras , Leveduras/metabolismo , Alimentos Fermentados/microbiologia , Bebidas/microbiologia , Alimento Funcional , Microbiologia de Alimentos , Humanos , Fenóis/metabolismo , Fenóis/análiseRESUMO
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".
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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.
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Ecossistema , Probióticos , Abelhas , Animais , Humanos , Células CACO-2 , Leveduras/metabolismo , CandidaRESUMO
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 ß-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.
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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.
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Ascomicetos , Microbioma Gastrointestinal , Abelhas , Animais , Leveduras/genética , Pichia , FloresRESUMO
Currently, an increasing number of intolerant and vegan consumers are driving the market towards plant-based milk alternatives. Here, selected probiotic yeasts, belonging to the Candida zeylanoides, Kluyveromyces lactis and Debaryomyces hansenii species, previously characterized for their aptitude to ferment animal milk, were tested in soy milk. Trials at different fermentation times with the developed yeast consortium (Yc) coinoculated with a lactic bacterium commercial strain were carried out. Yc showed good fermentation performance, conferring distinctive analytical and aromatic properties to the resulted soy fermented beverage, a product similar to an industrial kefir. Analytical determinations did not show significant variations between the end of fermentation and cold storage (4 weeks at 4 °C), indicating full stability. Phenol amounts and antioxidant activity were significantly increased in soy fermented beverage fermented by Yc. All yeasts remained viable until the end of storage with a final concentration of approximately 8 Log CFU/ml, a value suitable for a probiotic commercial claim. Overall, the results suggest that Yc is a promising multistarter candidate for functional soy products.
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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.
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Fermented food matrices, including beverages, can be defined as the result of the activity of complex microbial ecosystems where different microorganisms interact according to different biotic and abiotic factors. Certainly, in industrial production, the technological processes aim to control the fermentation to place safe foods on the market. Therefore, if food safety is the essential prerogative, consumers are increasingly oriented towards a healthy and conscious diet driving the production and consequently the applied research towards natural processes. In this regard, the aim to guarantee the safety, quality and diversity of products should be reached limiting or avoiding the addition of antimicrobials or synthetic additives using the biological approach. In this paper, the recent re-evaluation of non-Saccharomyces yeasts (NSYs) has been reviewed in terms of bio-protectant and biocontrol activity with a particular focus on their antimicrobial power using different application modalities including biopackaging, probiotic features and promoting functional aspects. In this review, the authors underline the contribution of NSYs in the food production chain and their role in the technological and fermentative features for their practical and useful use as a biocontrol agent in food preparations.
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Three killer toxins that were previously investigated, one excreted by Kluyveromyces wickerhamii and two by different strains of Wickerhamomyces anomalus, were produced at the pilot scale, lyophilized and characterized, and the formulates were assessed for their zymocidial effect against Brettanomyces bruxellensis spoilage yeast. A comparative analysis allowed the evaluation of the minimum inhibitory concentration (MIC) against a sensitive strain. Fungicidal and fungistatic concentrations were used to evaluate the cytocidal effect using a cytofluorimetric approach that confirmed the lethal effect of all lyophilized formulates against B. bruxellensis spoilage yeasts. Moreover, the potential killer toxins' cytotoxicity against human intestinal cells (Caco-2) were evaluated to exclude any possible negative effect on the consumers. Finally, the effective lethal effect of all three lyophilized killer toxins toward B. bruxellensis sensitive strain were tested. The results indicated that all of them acted without dangerous effects on the human epithelial cells, opening the way for their possible commercial application. In particular, D15 showed the lowest MIC and the highest activity, was evaluated also in wine, revealing a strong reduction of Brettamonyces yeast growth and, at the same time, a control of ethyl phenols production.
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Brettanomyces , Toxinas Biológicas , Vinho , Humanos , Células CACO-2 , Leveduras , Toxinas Biológicas/farmacologia , Microbiologia de AlimentosRESUMO
During the last few years, consumer demand has been increasingly oriented to fermented foods with functional properties. This work proposed to use selected non-conventional yeasts (NCY) Lachanceathermotolerans and Kazachstaniaunispora in pure and mixed fermentation to produce craft beer fortified with hydrolyzed red lentils (HRL). For this, fermentation trials using pils wort (PW) and pils wort added with HRL (PWL) were carried out. HRL in pils wort improved the fermentation kinetics both in mixed and pure fermentations without negatively affecting the main analytical characters. The addition of HRL determined a generalized increase in amino acids concentration in PW. L. thermotolerans and K. unispora affected the amino acid profile of beers (with and without adding HRL). The analysis of by-products and volatile compounds in PW trials revealed a significant increase of some higher alcohols with L. thermotolerans and ethyl butyrate with K. unispora. In PWL, the two NCY showed a different behavior: an increment of ethyl acetate (K. unispora) and ß-phenyl ethanol (L. thermotolerans). Sensory analysis showed that the presence of HRL characterized all beers, increasing the perception of the fruity aroma in both pure and mixed fermentation.
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Overall, 180 yeasts and bacteria isolated from the peel of citrus fruits were screened for their in vitro antagonistic activity against Penicillium digitatum and P. italicum, causative agents of green and blue mold of citrus fruits, respectively. Two yeast and three bacterial isolates were selected for their inhibitory activity on mycelium growth. Based on the phylogenetic analysis of 16S rDNA and ITS rDNA sequences, the yeast isolates were identified as Candida oleophila and Debaryomyces hansenii while the bacterial isolates were identified as Bacillus amyloliquefaciens, B. pumilus and B. subtilis. All five selected isolates significantly reduced the incidence of decay incited by P. digitatum and P. italicum on 'Valencia' orange and 'Eureka' lemon fruits. Moreover, they were effective in preventing natural infections of green and blue mold of fruits stored at 4 °C. Treatments with antagonistic yeasts and bacteria did not negatively affect the quality and shelf life of fruits. The antagonistic efficacy of the five isolates depended on multiple modes of action, including the ability to form biofilms and produce antifungal lipopeptides, lytic enzymes and volatile compounds. The selected isolates are promising as biocontrol agents of postharvest green and blue molds of citrus fruits.
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This paper reports on a common experiment performed by 17 Research Units of the Italian Group of Microbiology of Vine and Wine (GMVV), which belongs to the Scientific Society SIMTREA, with the aim to validate a protocol for the characterization of wine strains of Saccharomyces cerevisiae. For this purpose, two commercial S. cerevisiae strains (EC 1118 and AWRI796) were used to carry out inter-laboratory-scale comparative fermentations using both synthetic medium and grape musts and applying the same protocol to obtain reproducible, replicable, and statistically valid results. Ethanol yield, production of acetic acid, glycerol, higher alcohols, and other volatile compounds were assessed. Moreover, the Fourier transform infrared spectroscopy was also applied to define the metabolomic fingerprint of yeast cells from each experimental trial. Data were standardized as unit of compounds or yield per gram of sugar (glucose and fructose) consumed throughout fermentation, and analyzed through parametric and non-parametric tests, and multivariate approaches (cluster analysis, two-way joining, and principal component analysis). The results of experiments carried out by using synthetic must showed that it was possible to gain comparable results from three different laboratories by using the same strains. Then, the use of the standardized protocol on different grape musts allowed pointing out the goodness and the reproducibility of the method; it showed the main traits of the two yeast strains and allowed reducing variability amongst independent batches (biological replicates) to acceptable levels. In conclusion, the findings of this collaborative study contributed to the validation of a protocol in a specific synthetic medium and in grape must and showed how data should be treated to gain reproducible and robust results, which could allow direct comparison of the experimental data obtained during the characterization of wine yeasts carried out by different research laboratories.
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BACKGROUND: Botrytis cinerea (B. cinerea) is responsible for grape infection and damage to the winemaking and table grape sectors. Although anti-Botrytis chemicals are available, they are considered unsustainable for resistance phenomenon and adverse effects on the environment and human health. Research is focused on developing alternative approaches, such as exploiting biological control agents (BCAs). In this context, 19 yeasts of the genera Cryptococcus, Aureobasidium, Metschnikowia, Kluyveromyces and Wickerhamomyces were tested as antimicrobial agents against B. cinerea development. METHODS: A combination of in vitro tests based on dual-culture methods, volatile organic compound production assay, laboratory tests on grape berries (punctured and sprayed with yeasts) and field experiments based on yeast treatments on grapes in vineyards allowed the selection of two potential BCAs. RESULTS: M. pulcherrima DiSVA 269 and A. pullulans DiSVA 211 exhibited the best ability to contain the development of B. cinerea, showing the severity, the decay and the McKinney index lower than a commercial biological formulation consisting of a mixture of two different A. pullulans strains, which were used as positive controls. CONCLUSIONS: The results indicated that the selected strains were effective BCA candidates to counteract B. cinerea in the field, applying them in the partial or total replacement of conventional treatments.
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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.
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Fermentação/fisiologia , Vinho/microbiologia , Leveduras/metabolismo , Etanol/metabolismo , Humanos , Microbiota/fisiologia , Nutrientes/metabolismo , Saccharomyces/metabolismoRESUMO
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.
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Wickerhamomyces anomalus strain 18, isolated from a natural underground cheese ripening pit, secretes a mycocin named WA18 that inhibits wine spoilage yeasts belonging to Brettanomyces bruxellensis species, with a broad-spectrum of activity. WA18 was purified, and the purified protein was digested with specific restriction enzymes (lysine K and arginine R cut sites). The LC-MS and LC-MS/MS analysis after enzymatic digestions revealed a molecular weight of 31 kDa. Bioinformatics processing and database research of digested pure killer protein showed 99% identity with a UDP-glycosyltransferase protein. Competitive inhibition assay of killer activity by cell-wall polysaccharides suggests that branched glucans represent the first receptor site of the toxin on the envelope of the sensitive target. The WA18 partially purified crude extract (PPCE) showed high stability of antimicrobial activity at the physicochemical conditions suitable for the winemaking process. Indeed, in wine WA18 was able to counteract B. bruxellensis and control the production of ethyl phenols. In addition, the strain WA18 was compatible with Saccharomyces cerevisiae in co-culture conditions with a potential application together with commercial starter cultures. These data suggest that WA18 mycocin is a promising biocontrol agent against spoilage yeasts in winemaking, particularly during wine storage.
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This review describes the researches performed in the last years to assess the impact of pesticide sub-lethal doses on soil microorganisms and non-target organisms in agricultural soil ecosystems. The overview was developed through the careful description and a critical analysis of three methodologies based on culture-independent approaches involving DNA extraction and sequencing (denaturing gradient gel electrophoresis, DGGE; next-generation sequencing, NGS) to characterize the microbial population and DNA damage assessment (comet assay) to determine the effect on soil invertebrates. The examination of the related published articles showed a continuous improvement of the possibility to detect the detrimental effect of the pesticides on soil microorganisms and non-target organisms at sub-lethal doses, i.e., doses which have no lethal effect on the organisms. Considering the overall critical discussion on microbial soil monitoring in the function of pesticide treatments, we can confirm the usefulness of PCR-DGGE as a screening technique to assess the genetic diversity of microbial communities. Nowadays, DGGE remains a preliminary technique to highlight rapidly the main differences in microbial community composition, which is able to give further information if coupled with culture-dependent microbiological approaches, while thorough assessments must be gained by high-throughput techniques such as NGS. The comet assay represents an elective technique for assessing genotoxicity in environmental biomonitoring, being mature after decades of implementation and widely used worldwide for its direct, simple, and affordable implementation. Nonetheless, in order to promote the consistency and reliability of results, regulatory bodies should provide guidelines on the optimal use of this tool, strongly indicating the most reliable indicators of DNA damage. This review may help the European Regulation Authority in deriving new ecotoxicological endpoints to be included in the Registration Procedure of new pesticides.
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Sulfites and sulfides are produced by yeasts in different amounts depending on different factors, including growth medium and specific strain variability. In natural must, some strains can produce an excess of sulfur compounds that confer unpleasant smells, inhibit malolactic fermentation and lead to health concerns for consumers. In organic wines and in sulfite-free wines the necessity to limit or avoid the presence of sulfide and sulfite requires the use of selected yeast strains that are low producers of sulfur compounds, with good fermentative and aromatic aptitudes. In the present study, exploiting the sexual mass-mating spores' recombination of a native Saccharomyces cerevisiae strain previously isolated from grape, three new S. cerevisiae strains were selected. They were characterized by low sulfide and sulfite production and favorable aromatic imprinting. This approach, that occurs spontaneously also in nature, allowed us to obtain new native S. cerevisiae strains with desired characteristics that could be proposed as new starters for organic and sulfite-free wine production, able to control sulfur compound production and to valorize specific wine types.
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In the last decades, there has been a growing interest from consumers in their food choices. Organic, natural, less processed, functional, and pre-probiotic products were preferred. Although, Saccharomyces cerevisiae var. boulardii is the most well-characterized probiotic yeast available on the market, improvement in probiotic function using other yeast species is an attractive future direction. In the present study, un-anthropized natural environments and spontaneous processed foods were exploited for wild yeast isolation with the goal of amplifying the knowledge of probiotic aptitudes of different yeast species. For this purpose, 179 yeast species were isolated, identified as belonging to twelve different genera, and characterized for the most important probiotic features. Findings showed interesting probiotic characteristics for some yeast strains belonging to Lachancea thermotolerans, Metschnikowia ziziphicola, Saccharomyces cerevisiae, and Torulaspora delbrueckii species, although these probiotic aptitudes were strictly strain-dependent. These yeast strains could be proposed for different probiotic applications, such as a valid alternative to, or in combination with, the probiotic yeast S. cerevisiae var. boulardii.
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One of the most important problems in the winemaking field is the increase of ethanol content in wine. Wines with high ethanol level negatively affect wine flavor and human health. In this study, we evaluated the use of a selected strain of Metschnikowia pulcherrima in immobilized form and under different aeration conditions, to reduce the ethanol content evaluating the volatile profile of the resulting wines. In a preliminary screening the best conditions regarding free/immobilized cells, static/aerated fermentation and inoculation level were identified. Bench-Top fermentation trials with different aeration conditions showed that the use of M. pulcherrima selected strain with aeration flow of 20 mL/L/min during the first 72 h of fermentation, led an ethanol reduction of 1.38% (v/v) in comparison with Saccharomyces cerevisiae control strain. The analytical profile of the resulting wines did not show any negative feature. Indeed, the concentration of ethyl acetate, that above its sensory threshold impacts negatively the wine sensory profile, was found at an acceptable level. On the other hand, an increase in the concentration of significant fruity and flower compounds was found.