New perspectives in safety and quality enhancement of wine through selection of yeasts based on the parietal adsorption activity

Ochratoxin A in Dry-Cured Ham: OTA-Producing Fungi, Prevalence, Detection Methods, and Biocontrol Strategies-A Review

Traditional dry-cured hams are easily contaminated by toxigenic fungi during the fermentation and ripening stages. The detection and positive rates of ochratoxin A (OTA) are the highest among mycotoxins detected in traditional dry-cured hams, indicating that OTA in hams is a potential safety hazard to human health. This review addresses the mycotoxin-producing fungal species, the toxigenic conditions causing OTA contamination worldwide, the prevalence of OTA contamination in dry-cured hams, and the detection methods applied in OTA analysis. Additionally, this study introduces methods to prevent and control OTA in traditional dry-cured hams. The growth of common mycotoxin-producing fungi and the accumulation of mycotoxins in dry-cured ham can be controlled by a microbial starter. This review provides an important theoretical foundation for the research and control of OTA in traditional dry-cured hams.

Modulation of extracellular Penicillium expansum-driven acidification by Papiliotrema terrestris affects biosynthesis of patulin and has a possible role in biocontrol activity

The active regulation of extracellular pH is critical for the virulence of fungal pathogens. Penicillium expansum is the causal agent of green-blue mold on stored pome fruits and during its infection process acidifies the host tissues by secreting organic acids. P. expansum is also the main producer of patulin (PAT), a mycotoxin found in pome fruit-based products and that represents a serious health hazard for its potential carcinogenicity. While it is known that PAT biosynthesis in P. expansum is regulated by nutritional factors such as carbon and nitrogen and by the pH, the mechanistic effects of biocontrol on PAT production by P. expansum are not known. In this work, we assessed how optimal and suboptimal concentrations of the biocontrol agent (BCA) Papiliotrema terrestris LS28 affect both extracellular pH and PAT biosynthesis in P. expansum. In wounded apples, the optimal and suboptimal concentrations of the BCA provided almost complete and partial protection from P. expansum infection, respectively, and reduced PAT contamination in both cases. However, the suboptimal concentration of the BCA increased the specific mycotoxigenic activity by P. expansum. In vitro, the rate of PAT biosynthesis was strictly related to the extracellular pH, with the highest amount of PAT detected in the pH range 4–7, whereas only traces were detectable at pH 3. Moreover, both in vitro and in apple wounds the BCA counteracted the extracellular P. expansum-driven acidification maintaining extracellular pH around 4, which is within the pH range that is optimal for PAT biosynthesis. Conversely, in the absence of LS28 the pathogen-driven acidification led to rapidly achieving acidic pH values (<3) that lie outside of the optimal pH range for PAT biosynthesis. Taken together, these results suggest that pH modulation by LS28 is important to counteract the host tissue acidification and, therefore, the virulence of P. expansum. On the other hand, the buffering of P. expansum-driven acidification provided by the BCA increases the specific rate of PAT biosynthesis through the extension of the time interval at which the pH value lies within the optimal range for PAT biosynthesis. Nevertheless, the antagonistic effect provided by the BCA greatly reduced the total amount of PAT.

Microencapsulation of Hibiscus sabdariffa L. Calyx Anthocyanins with Yeast Hulls

Yeast hulls, due to their specific thin mannoprotein layer and high content of β-glucan, constitute a promising material to stabilise the colour of anthocyanins. This study evaluates the potential of yeast hulls on the freeze-drying encapsulation of anthocyanins-rich extract from Hibiscus sabdariffa L. calyx with comparison to maltodextrin microcapsules. The moisture content (5.28-16.38%), water activity (< 0.039-0.307) and hygroscopicity (17.50-25.99 g/100 g) of obtained powders were evaluated. The stability of encapsulated anthocyanins, monitored through the total anthocyanin content, was evaluated with the pH differential method immediately after production and after a 10-week storage under different conditions of temperature (5 or 37 °C), humidity (45 or 85% RH), in presence or absence of light. The colour parameters (a, b*, L*, C*, H°, ΔE^*) of powders were measured. The results indicated that yeast-hulls showed a good ability to protect anthocyanin against the influence of temperature, light, moisture compared to freeze-dried anthocyanins-rich extracts (p < 0.05). Yeast hulls protected anthocyanin better than maltodextrin under high humidity conditions (p < 0.05).

Microbiological Decontamination of Mycotoxins: Opportunities and Limitations

The contamination of food and feeds with mycotoxins poses a global health risk to humans and animals, with major economic consequences. Good agricultural and manufacturing practices can help control mycotoxin contamination. Since these actions are not always effective, several methods of decontamination have also been developed, including physical, chemical, and biological methods. Biological decontamination using microorganisms has revealed new opportunities. However, these biological methods require legal regulations and more research before they can be used in food production. Currently, only selected biological methods are acceptable for the decontamination of feed. This review discusses the literature on the use of microorganisms to remove mycotoxins and presents their possible mechanisms of action. Special attention is given to Saccharomyces cerevisiae yeast and lactic acid bacteria, and the use of yeast cell wall derivatives.

Application of adsorption process for effective removal of emerging contaminants from water and wastewater

Emerging pollutants in the marine ecosystem, as well as their possible impact on live species, have become a rising cause of worry. A traditional wastewater treatment plants alone are not successful in eliminating such massive contaminant groups and therefore additional water treatment is required which is to be cost effective. Since standard primary and secondary treatment plants are unsuccessful at eliminating or degrading these harmful chemicals, a cost-effective tertiary treatment approach is proposed. Adsorption is a successful approach for Contaminants removal globally, because it is low installation expense, high performance and has easy operational design. Emerging pollutants have been removed from wastewaters using various adsorbents like activated carbons, improved bio chars, Nano adsorbents, hybrid adsorbents, and others. The purpose of this paper is to review the source of contaminants and the concept of adsorption when separating emerging contaminants. The present study aims to examine the adsorption mechanism as an effective approach for treating emerging contaminants. Then, the analysis of natural and man-made adsorbents for the separation of contaminants is examined along with its comparison. Also, future view on emerging contaminants and adsorbents in modern generation has been discussed.

Oenological Potential of Autochthonous Saccharomyces cerevisiae Yeast Strains from the Greek Varieties of Agiorgitiko and Moschofilero

Nemea and Mantinia are famous wine regions in Greece known for two indigenous grape varieties, Agiorgitiko and Moschofilero, which produce high quality PDO wines. In the present study, indigenous Saccharomyces cerevisiae yeast strains were isolated and identified from spontaneous alcoholic fermentation of Agiorgitiko and Moschofilero musts in order to evaluate their oenological potential. Random amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR) recovered the presence of five distinct profiles from a total of 430 yeast isolates. The five obtained strains were evaluated at microvinifications trials and tested for basic oenological and biochemical parameters including sulphur dioxide and ethanol tolerance as well as H2S production in sterile grape must. The selected autochthonous yeast strains named, Soi2 (Agiorgitiko wine) and L2M (Moschofilero wine), were evaluated also in industrial (4000L) fermentations to assess their sensorial and oenological characteristics. The volatile compounds of the produced wines were determined by GC-FID. Our results demonstrated the feasibility of using Soi2 and L2M strains in industrial fermentations for Agiorgitiko and Moschofilero grape musts, respectively.

Optimised Extraction and Preliminary Characterisation of Mannoproteins from Non-Saccharomyces Wine Yeasts

The exogenous application of yeast-derived mannoproteins presents many opportunities for the improvement of wine technological and oenological properties. Their isolation from the cell wall of Saccharomycescerevisiae has been well studied. However, investigations into the efficiency of extraction methods from non-Saccharomyces yeasts are necessary to explore the heterogeneity in structure and composition that varies between yeast species, which may influence wine properties such as clarity and mouthfeel. In this study, nine yeast strains were screened for cell wall mannoprotein content using fluorescence microscopy techniques. Four species were subsequently exposed to a combination of mechanical and enzymatic extraction methods to optimize mannoprotein yield. Yeast cells subjected to 4 min of ultrasound treatment applied at 80% of the maximum possible amplitude with a 50% duty cycle, followed by an enzymatic treatment of 4000 U lyticase per g dry cells weight, showed the highest mannoprotein-rich yield from all species. Furthermore, preliminary evaluation of the obtained extracts revealed differences in carbohydrate/protein ratios between species and with increased enzyme incubation time. The results obtained in this study form an important step towards further characterization of extraction treatment impact and yeast species effect on the isolated mannoproteins, and their subsequent influence on wine properties.

Construction and screening of a glycosylphosphatidylinositol protein deletion library in Pichia pastoris

Background

Glycosylphosphatidylinositol (GPI)-anchored glycoproteins have diverse intrinsic functions in yeasts, and they also have different uses in vitro. In this study, the functions of potential GPI proteins in Pichia pastoris were explored by gene knockout approaches.

Results

Through an extensive knockout of GPI proteins in P. pastoris, a single-gene deletion library was constructed for 45 predicted GPI proteins. The knockout of proteins may lead to the activation of a cellular response named the ‘compensatory mechanism’, which is characterized by changes in the content and relationship between cell wall polysaccharides and surface proteins. Among the 45 deletion strains, five showed obvious methanol tolerance, four owned high content of cell wall polysaccharides, and four had a high surface hydrophobicity. Some advantages of these strains as production hosts were revealed. Furthermore, the deletion strains with high surface hydrophobicity were used as hosts to display Candida antarctica lipase B (CALB). The strain gcw22Δ/CALB-GCW61 showed excellent fermentation characteristics, including a faster growth rate and higher hydrolytic activity.

Conclusions

This GPI deletion library has some potential applications for production strains and offers a valuable resource for studying the precise functions of GPI proteins, especially their putative functions.

Non-Saccharomyces Yeasts and Organic Wines Fermentation: Implications on Human Health

A relevant trend in winemaking is to reduce the use of chemical compounds in both the vineyard and winery. In organic productions, synthetic chemical fertilizers, pesticides, and genetically modified organisms must be avoided, aiming to achieve the production of a “safer wine”. Safety represents a big threat all over the world, being one of the most important goals to be achieved in both Western society and developing countries. An occurrence in wine safety results in the recovery of a broad variety of harmful compounds for human health such as amines, carbamate, and mycotoxins. The perceived increase in sensory complexity and superiority of successful uninoculated wine fermentations, as well as a thrust from consumers looking for a more “natural” or “organic” wine, produced with fewer additives, and perceived health attributes has led to more investigations into the use of non-Saccharomyces yeasts in winemaking, namely in organic wines. However, the use of copper and sulfur-based molecules as an alternative to chemical pesticides, in organic vineyards, seems to affect the composition of grape microbiota; high copper residues can be present in grape must and wine. This review aims to provide an overview of organic wine safety, when using indigenous and/or non-Saccharomyces yeasts to perform fermentation, with a special focus on some metabolites of microbial origin, namely, ochratoxin A (OTA) and other mycotoxins, biogenic amines (BAs), and ethyl carbamate (EC). These health hazards present an increased awareness of the effects on health and well-being by wine consumers, who also enjoy wines where terroir is perceived and is a characteristic of a given geographical area. In this regard, vineyard yeast biota, namely non-Saccharomyces wine-yeasts, can strongly contribute to the uniqueness of the wines derived from each specific region.

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

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

Influence of Saccharomyces and non-Saccharomyces Yeasts in the Formation of Pyranoanthocyanins and Polymeric Pigments during Red Wine Making

Yeast are able to modulate many sensory parameters of wines during red must fermentation. The effect on color and on the formation of derived pigments during fermentation has been studied thoroughly since the 90s. Yeast can increase grape anthocyanin’s color by acidification by hyperchromic effect (increase of flavylium molecules). Recent studies with non-Saccharomyces species, as Lachancea thermotolerans, described the intense effect of some strains on anthocyanin’s color, and subsequent, stability, by strongly reducing wine’s pH during fermentation. Moreover, selected yeast strains of Saccharomyces have been shown to release metabolites such as pyruvic acid or acetaldehyde that promote the formation of vitisin A and B pyranoanthocyanins during must fermentation. Schizosaccharomyces pombe, because of its specific metabolism, can produce higher concentrations of pyruvate, which enhances the formation of vitisin A-type derivatives. The hydroxycinnamate decarboxylase activity that some Saccharomyces strains express during fermentation also promotes the formation of vinylphenolic derivatives. Some non-Saccharomyces species, such as S. pombe or P. guilliermondii can also improve the production of these derivatives compared to selected strains of Saccharomyces cerevisiae. Lastly, some yeasts are also able to modulate the formations of polymeric pigments between grape anthocyanins and flavonoids, such as catechins and procyanidins.

Mannoprotein Content and Volatile Molecule Profiles of Trebbiano Wines Obtained by Saccharomyces cerevisiae and Saccharomyces bayanus Strains

: The production of volatile compounds has become one of the major technological features for yeast selection. In fact, although the aromatic profile of the wine is the sum of varietal-, pre-, post-, and fermentative-aroma compound, yeasts affect the quality of the grape from maturation throughout fermentation, metabolizing sugars and other components into alcohols, esters, organic acids, and aldehydes. Among the new technological features, the production of mannoproteins has gained interest. From this perspective, the main aim of this work was to characterize 9 strains of Saccharomyces cerevisiae and 1 of Saccharomyces bayanus for their volatile profiles and the release of mannoproteins. The strains were inoculated in Trebbiano musts and incubated at 15 °C; at the end of fermentation the wines were evaluated by GC/MS/SPME for their volatile profiles and mannoprotein content by enzymatic assay. The strains were inoculated at level ranging between 4.9 and 6.3 log CFU/mL but only the strains L318 and 12233X6167 were able to reach values of 7.5 log CFU/mL. The aromatic profiles resulted in a strain-specific fingerprinting. According to the principal component analysis, the wines produced by the strains L288, L234, and L318 were characterized by the presence of propanoic acid, butanol, octanoic acid, and 3 methyl pentanol while the wine obtained by the strain 12233x35G2 was characterized by the presence of propanoic acid, butanol, octanoic acid and 3 methyl pentanol while the strain 12233x35G2 was characterized by the presence of decanoic acid ethyl ester, heptanoic acid ethyl ester, and acetic acid 2 phenetyl ester. Regarding mannoproteins, the highest concentration was achieved by strain12233x6167 (104 mg/L). The data allowed to select the strains endowed with the best fermentation performances in terms of aroma and mannoproteins release.

Use of Saccharomyces cerevisiae var. boulardii in co-fermentations with S. cerevisiae for the production of craft beers with potential healthy value-added

In recent years, the awareness of consumers about the impact of food on health is constantly increasing. A high amount of dietary antioxidant intake can be supplied by beverages widely consumed, such as wine, coffee, beer. Recently, an increase in the consumer interest was observed for beer, in consequence of the high phenolic antioxidants and low ethanol content present in this beverage. Among all beer types, in recent years, consumption of craft beers has gained popularity. Being an unpasteurized and unfiltered, craft beer is potentially a new vehicle for delivering health effects. While health benefits of lactic acid bacteria as probiotics are well known, few data are available on probiotic yeasts in fermented food. Therefore, this study was aimed to analyse the effect of integrating the well-known probiotic yeast strain of S. cerevisiae var. boulardii (S.b) in mixed cultures with S. cerevisiae strains for production of beers with increased healthy benefits. The probiotic strain of S.b was tested in mixed cultures with selected S. cerevisiae strains, during wort fermentation. As the viability during processing operations is one of the criteria for selecting suitable strains of probiotic microorganisms, the survival of probiotic yeast during the fermentation and the presence of highly viable cells at the end of fermentations were evaluated. In almost all the mixed fermentations, at the end of the process the probiotic yeast was predominant on S. cerevisiae strain, and the experimental beers contained a high number of viable cells of S.b strain (ranging between 8 × 10⁶ and 7.0 × 10⁷/mL). The analysis of experimental beers for the content of main volatile compounds showed that the inclusion of S.b strain in mixed starter did not affect negatively beer aroma. Moreover, the inclusion of S.b strain in mixed starters determined an increase in the antioxidant activity and polyphenols content, in comparison to beers from single starter fermentations, indicating the influence of S.b strain on these parameters. Some mixed starter cultures tested in this study resulted a very promising tool to increase the healthy quality of the product, such as the improve the antioxidant activity and polyphenols content of beer.

Application of Low-Fermenting Yeast Lachancea thermotolerans for the Control of Toxigenic Fungi Aspergillus parasiticus, Penicillium verrucosum and Fusarium graminearum and Their Mycotoxins

Mycotoxins are important contaminants of food and feed. In this study, low fermenting yeast (Lachancea thermotolerans) and its derivatives were applied against toxigenic fungi and their mycotoxins. A. parasiticus, P. verrucosum and F. graminearum and their mycotoxins were exposed to yeast volatile organic compounds (VOCs) and cells, respectively. VOCs reduced significantly the fungal growth (up to 48%) and the sporulation and mycotoxin synthesis (up to 96%). Very interestingly, it was shown that even 7 yeast colonies reduced Fusarium’s growth and the synthesis of its mycotoxin, deoxynivalenol (DON). Moreover, decreasing yeast nutrient concentrations did not affect the inhibition of fungal growth, but reduced DON synthesis. In addition, inactivated yeast cells were able to remove up to 82% of the ochratoxin A (OTA). As an application of these findings, the potentialities of the VOCs to protect tomatoes inoculated with F. oxysporum was explored and showed that while in the presence of VOCs, no growth was observed of F. oxysporum on the inoculated surface areas of tomatoes, in the absence of VOCs, F. oxysporum infection reached up to 76% of the tomatoes’ surface areas. These results demonstrate that the application of yeasts and their derivatives in the agriculture and food industry might be considered as a very promising and safe biocontrol approach for food contamination.

Bioactive Compounds of Chamber-Dried Blueberries at Controlled Temperature and Wines Obtained from Them

The effects of chamber drying under controlled temperature and moisture conditions and fermentation process on blueberry juices to obtain three wines were studied in this work. Drying was carried out with a view to increase the sugar content and obtain wines with an ethanol content similar to a commercial grape wine or to obtain sweet wines. Analyses included color parameters; browning index; and anthocyanin, flavonols, flavan-3-ol derivatives, and tannin concentrations, as well as vitamin C concentration and antioxidant activity. Based on the results, drying increases color and the concentration of anthocyanins and tannins most probably by the effect of dehydration of the berries and diffusion of the colored compounds from the skin to the pulp due to the structural alterations in their skin. In addition, drying decreases flavonols, flavan-3-ol derivatives, and vitamin C concentrations. The browning index, anthocyanins, and tannins decreased with the fermentation time, and vitamin C was constant with the fermentation time. The sensory analysis showed that the wines with the best sensory characteristics were those with residual sugar, partial fermented wines 1 and 2.

Differential Adsorption of Ochratoxin A and Anthocyanins by Inactivated Yeasts and Yeast Cell Walls during Simulation of Wine Aging

The adsorption of ochratoxin A (OTA) by yeasts is a promising approach for the decontamination of musts and wines, but some potential competitive or interactive phenomena between mycotoxin, yeast cells, and anthocyanins might modify the intensity of the phenomenon. The aim of this study was to examine OTA adsorption by two strains of Saccharomyces cerevisiae (the wild strain W13, and the commercial isolate BM45), previously inactivated by heat, and a yeast cell wall preparation. Experiments were conducted using Nero di Troia red wine contaminated with 2 μg/L OTA and supplemented with yeast biomass (20 g/L). The samples were analyzed periodically to assess mycotoxin concentration, chromatic characteristics, and total anthocyanins over 84 days of aging. Yeast cell walls revealed the highest OTA-adsorption in comparison to thermally-inactivated cells (50% vs. 43% toxin reduction), whilst no significant differences were found for the amount of adsorbed anthocyanins in OTA-contaminated and control wines. OTA and anthocyanins adsorption were not competitive phenomena. Unfortunately, the addition of yeast cells to wine could cause color loss; therefore, yeast selection should also focus on this trait to select the best strain.

Wood impregnation of yeast lees for winemaking

This study develops a new method to produce more complex wines by means of an indirect diffusion of wood aromas from yeast cell-walls. An exogenous lyophilized biomass was macerated with an ethanol wood extract solution and subsequently dried. Different times were used for the adsorption of polyphenols and volatile compounds to the yeast cell-walls. The analysis of polyphenols and volatile compounds (by HPLC/DAD and GC-MS, respectively) demonstrate that the adsorption/diffusion of these compounds from the wood to the yeast takes place. Red wines were also aged with Saccharomyces cerevisiae lees that had been impregnated with wood aromas and subsequently dried. Four different types of wood were used: chestnut, cherry, acacia and oak. Large differences were observed between the woods studied with regards to their volatile and polyphenolic profiles. Sensory evaluations confirmed large differences even with short-term contact between the wines and the lees, showing that the method could be of interest for red wine making. In addition, the results demonstrate the potential of using woods other than oak in cooperage.

Sorption of grape proanthocyanidins and wine polyphenols by yeasts, inactivated yeasts, and yeast cell walls

Inactivated yeast fractions (IYFs) can be used in enology to improve the stability and mouthfeel of red wines. However, information concerning the mechanisms involved and the impact of the IYF characteristics is scarce. Adsorption isotherms were used to investigate interactions between grape proanthocyanidin fractions (PAs) or wine polyphenols (WP) and a commercial yeast strain (Y), the inactivated yeast (IY), the yeast submitted to autolyzis and inactivation (A-IY), and the cell walls obtained by mechanical disruption (CW). High affinity isotherms and high adsorption capacities were observed for grape PAs and whole cells (Y, IY, and A-IY). Affinity and adsorbed amount were lower with wine PAs, due to chemical changes occurring during winemaking. By contrast to whole cells, grape PAs and WP adsorption on CW remained very low. This raises the issue of the part played by cell walls in the interactions between yeast and proanthocyanidins and suggests the passage of the latter through the wall pores and their interaction with the plasma membrane.

Ochratoxin A released back into the medium by Saccharomyces cerevisiae as a function of the strain, washing medium and fermentative conditions

BACKGROUND

This study was aimed at investigating the removal of ochratoxin A (OTA) by two wild strains of Saccharomyces cerevisiae (W20 and W30) in a semi-synthetic medium under two temperatures (25, 30 °C) and sugar levels (200, 250 g L(-1) ), as well as the stability of OTA-yeast complex by evaluating the amount of bound toxin released back after some washing treatments with phosphate-buffered saline (PBS) or model wine (MW). In addition, the main products of fermentation were studied.

RESULTS

Both W20 and W30 strains reduced OTA with removal percentages of 5.41-49.58%, and this process was affected by temperature and sugar concentration. Concerning the stability of the OTA-yeast complex, the amount of bound toxin decreased by 20-99% after five passes of washing, with a strong strain dependence and an effect of temperature and sugar concentration only for the W30 isolate. In addition, the two strains showed interesting technological properties in terms of fermentation products in a semi-synthetic medium (high ethanol yield, volatile acidity as acetic acid < 1.2 g L(-1) ; glycerol production exceeding 5.2 g L(-1) ).

CONCLUSIONS

Apart from the removal of OTA, release of the toxin is a variable process and relies upon the strain effect; a significance of the other factors of the design (sugar concentration, temperature) was found only for a single isolate. Thus evaluation of the stability of the complex yeasts/OTA should be an additional trait to select promising functional yeasts.

Use of non-Saccharomyces wine yeasts as novel sources of mannoproteins in wine

Eight non-Saccharomyces wine strains, previously selected for their ability to modulate the final concentrations of various volatile compounds and to persist with Saccharomyces cerevisiae in mixed inocula fermentations of grape juice, have been analyzed in the present work to test their ability to release mannoproteins. The eight strains were members of different genera originally isolated from grape: Hansensiaspora osmophila, Lachancea thermotolerans, Metschnikowia pulcherrima, Pichia fermentans, Saccharomycodes ludwigii, Starmerella bacillaris, Torulaspora delbrueckii and Zygosaccharomyces florentinus. A synthetic polysaccharide-free grape juice, was used to characterize the mannoproteins released during the alcoholic fermentation. Mannoproteins profiles were characterized by gel electrophoresis and carbohydrate composition was analyzed both by HPLC and by mass spectrometry. The eight non-Saccharomyces yeasts demonstrated a higher capacity to release polysaccharides compared to S. cerevisiae. The proteins released by the eight yeast strains showed a wide variety of protein sizes, ranging from 25 kDa to greater than 250 kDa. The mass spectrometric profile of the N-glycans ranged from 1600 to 4000 Da and was characteristic for each strain. Detailed investigation of the degree of polymerization of released N-glycans revealed variable composition from 8 to 15 units of monosaccharides.

Metabolic and transcriptomic response of the wine yeast Saccharomyces cerevisiae strain EC1118 after an oxygen impulse under carbon-sufficient, nitrogen-limited fermentative conditions

During alcoholic fermentation, Saccharomyces cerevisiae is exposed to continuously changing environmental conditions, such as decreasing sugar and increasing ethanol concentrations. Oxygen, a critical nutrient to avoid stuck and sluggish fermentations, is only discretely available throughout the process after pump-over operation. In this work, we studied the physiological response of the wine yeast S. cerevisiae strain EC1118 to a sudden increase in dissolved oxygen, simulating pump-over operation. With this aim, an impulse of dissolved oxygen was added to carbon-sufficient, nitrogen-limited anaerobic continuous cultures. Results showed that genes related to mitochondrial respiration, ergosterol biosynthesis, and oxidative stress, among other metabolic pathways, were induced after the oxygen impulse. On the other hand, mannoprotein coding genes were repressed. The changes in the expression of these genes are coordinated responses that share common elements at the level of transcriptional regulation. Beneficial and detrimental effects of these physiological processes on wine quality highlight the dual role of oxygen in 'making or breaking wines'. These findings will facilitate the development of oxygen addition strategies to optimize yeast performance in industrial fermentations.

Ochratoxin A removal by Saccharomyces cerevisiae strains: effect of wine-related physicochemical factors

BACKGROUND

This study investigated the effect of some physicochemical parameters on the removal of ochratoxin A (OTA) by yeasts.

RESULTS

Two wild strains of Saccharomyces cerevisiae (W47 and Y28) were used to assess OTA removal under various conditions of temperature, pH, ethanol content and incubation time. All samples were analysed for OTA concentration by enzyme-linked immunosorbent assay (ELISA). In addition, yeast oenological traits were investigated: qualitative and technological traits were assessed on appropriate laboratory media, while the main products of microfermentation (sugars, ethanol, glycerol, acetic acid) were evaluated by Fourier transform infrared spectroscopy (FTIR). The results showed OTA reduction by 36-42% in cultures containing 100 g L⁻¹ ethanol incubated at pH 3.5 and 37 °C.

CONCLUSION

OTA removal was affected by contact time, pH and ethanol content, as it was increased at low pH and by 100 g L⁻¹ ethanol. Moreover, the phenomenon was reversible, as OTA was lowest after 4 days, then it was partially released in the medium.

Quantification and characterization of cell wall polysaccharides released by non-Saccharomyces yeast strains during alcoholic fermentation

In order to improve knowledge about the oenological characteristics of non-Saccharomyces yeast strains, and to reconsider their contribution to wine quality, we studied the release of polysaccharides by 13 non-Saccharomyces strains of different species (three wine yeasts, six grape yeasts, and three spoilage yeasts) during alcoholic fermentation in synthetic must. Three Saccharomyces cerevisiae strains were included for comparison. All of the non-Saccharomyces strains released polysaccharides into fermentation medium; the amount released depended on the yeast species, the number of cells formed and their physiological conditions. Normalizing the quantity of macromolecules released to the cell biomass revealed that most non-Saccharomyces strains produced a greater quantity of polysaccharides compared to S. cerevisiae strains after 7 and 14days of fermentation. This capacity was particularly expressed in the studied wine spoilage yeasts (Saccharomycodes ludwigii, Zygosaccharomyces bailii, and Brettanomyces bruxellensis). Chemical characterization of exocellular polysaccharides produced by non-Saccharomyces yeasts revealed them to essentially be mannoproteins with high mannose contents, ranging from 93% for S'codes. ludwigii to 73-74% for Pichia anomala and Starmerella bombicola. Protein contents varied from 9% for P. anomala to 29% for Z. bailii. These compositions were very similar to those of the S. cerevisiae strains, and to the chemical composition of the cell wall mannoproteins of different yeast species. The presence of galactose, in addition to mannose and glucose, in the exocellular polysaccharides released by Schizosaccharomyces pombe, confirmed the parietal nature of the polysaccharides released by non-Saccharomyces yeasts; only this species has a galactomannan located in the outer layer of the cell wall.

Biocontrol of Penicillium nordicum growth and ochratoxin A production by native yeasts of dry cured ham

Twelve yeast strains isolated from the surface of Italian typical dry-cured hams, belonging to D. hansenii, D. maramus, C. famata, C. zeylanoides and H. burtonii species, and previously selected for their ability to grow in dry-cured ham-like substrates, were screened for antagonistic activity against a toxigenic strain of P. nordicum and inhibition of ochratoxin A (OTA) biosynthesis. On average, yeast inhibitory activity was lowered by increasing fungal inoculum and enhanced by NaCl presence. In the assay conditions, H. burtonii and C. zeylanoides were the most effective, both in inhibiting P. nordicum growth and OTA production. D. hansenii was the species with the lowest inhibitory activity, especially in the absence of salt. OTA production dropped from the range < LOD - 5000 ppb in P. nordicum control plates to the range < LOD - 200 ppb in yeast-added plates. OTA production increased in the presence of NaCl in P. nordicum control plates, while salt enhanced inhibition against OTA production in yeast-added plates.

Wine features related to safety and consumer health: an integrated perspective

This review presents a global view of the current situation of the scientific knowledge about aspects of wine with possible repercussions (positive or negative) on consumer health and wine safety. The presence in wine of some potential harmful compounds such as phytosanitary products, trace metal compounds, sulfites, and some toxics of microbial origin, such as ochratoxin A, ethyl carbamate, and biogenic amines, is discussed. The different strategies and alternative methodologies that are being carried out to reduce or to avoid the presence of these substances in wines are also discussed. In recent years much work has focused on establishing the scientific explanations for the positive biological effects of some wine compounds. In this review, we also examine the latest knowledge regarding wine and health, focusing on two types of compounds that have been related to the positive effects of moderate wine consumption, such as phenolic compounds and bioactive peptides.

Sparkling wines: features and trends from tradition

Sparkling wines contain at least three CO₂ pressure bars at 20°C. Carbonic gas is required to have an endogenous origin, obtained via a second fermentation, in the following European categories: sparkling wines and quality sparkling wines. In these types of sparkling wines, high gas pressure, together with other wine components, enables them to produce effervescence and foam when poured into the glass. The most commonly used grape varieties are Chardonnay and Pinot. Elaboration consists of two phases. In the first phase, the base wine is obtained after applying white vinification. The second phase consists of refermenting the wine, either in the bottle (champenoise or traditional method) or in isobaric tanks (Charmat method). The second fermentation requires the addition of "liqueur de tirage" to the base wine. The sparkling wines have a special biological aging or aging sur lies. As sparkling wines remain in contact with the lees, they develop sensory notes such as toasty, lactic, sweet, and yeasty, which can be attributed to proteolytic processes, components that would serve as the substrate for chemical and enzymatic reactions and to causes related with release-absorption between cell walls and the wine.

Binding of zearalenone, aflatoxin B1, and ochratoxin A by yeast-based products: a method for quantification of adsorption performance

A methodology was developed to quantify the efficiency of yeast-based products for adsorption of three mycotoxins: zearalenone (ZEA), aflatoxin B(1) (AFB(1)), and ochratoxin A (OTA). Eight products were tested (yeast cell wall or inactivated yeast). The described experimental protocol based on in vitro tests provided reliable isotherms for each mycotoxin. The most suitable models were the Hill model for ZEA, the Langmuir model for AFB(1), and the Freundlich model for OTA. From these models, original mathematical affinity criteria were defined to quantify the product adsorption performances for each mycotoxin. The best yeast product, a yeast cell wall from baker's yeast, can adsorb up to 68% of ZEA, 29% of AFB(1), and 62% of OTA, depending on the mycotoxin concentrations. The adsorption capacity largely depended both on yeast composition and mycotoxin, but no direct correlation between yeast composition and adsorption capacity was found, confirming that adsorption of mycotoxin on yeast-based products involves complex phenomena. The results of this study are useful for comparing the adsorption efficiency of various yeast products and understanding the mechanisms involved in adsorption.

Sugar levels in Charmat sparkling wines can affect the quality and resveratrol levels

Sparkling wines contain CO(2) obtained through a second fermentation by natural processes (Charmat method); they may be prepared with variable final sugar concentrations, resulting in physicochemical compositions and phenolic profiles different to those obtained with other natural methods. The purpose of this study was to verify the influence of sweetness on enological parameters, trans-resveratrol and trans-piceid levels, antioxidant capacity (power of scavenger the radical DPPH(•) (1,1-diphenyl-2-picrylhydrazyl) and mimetic enzymatic activities of superoxide dismutase (SOD-like) and catalase (CAT-like) assays, and β-glucosidase activities on Charmat sparkling wines. The interaction of polyphenol levels and sweetness was observed. Levels of trans-piceid and trans-resveratrol showed a decrease in function of glucose concentration up to 40 g/l. All samples showed antioxidant capacity and β-glucosidase activity was stable even in the presence of sugar. A positive correlation between SOD-like and DPPH(•) was observed. This work shows an approach able to clarify important aspects for the wine industry with regard to world-wide consumer demand for sweetened products.

Use of Saccharomyces cerevisiae strains endowed with β-glucosidase activity for the production of Sangiovese wine

The aim of this work was to evaluate the suitability of four strains of Saccharomyces cerevisiae endowed with in vitro β-glucosidase activity to improve the Sangiovese wine aroma profiles. In particular the effects of the strains on fermentation kinetics, wine sugar and acid concentrations, volatile molecule profiles and colour parameters were evaluated. Moreover their effects on anthocyanins, anthocyanidins and poliphenols were evaluated. These four strains of S. cerevisiae were tested in comparison with one commercial strain and with a spontaneous fermentation in the presence and in the absence of paraffin oil. The results showed that the four wild strains had high fermentation rates and an efficient conversion of grape sugars to alcohol. However, each strain imparted specific features to the wine. AS11 and AS15 gave rise to wine having low volatile acidity values associated to high levels of linalool and nerolidol. They provoked decrease of anthocyanins accompanied by the increase of some anthocyanidins. S. cerevisiae BV12 and BV14 showed the best performances producing wines with the lowest residual sugar contents and volatile acidity values, high levels of nerolidol and citronellol without detrimental effects on wine colour.

Role of specific components from commercial inactive dry yeast winemaking preparations on the growth of wine lactic acid bacteria

The role of specific components from inactive dry yeast preparations widely used in winemaking on the growth of three representative wine lactic acid bacteria (Oenococcus oeni, Lactobacillus hilgardii and Pediococcus pentosaceus) has been studied. A pressure liquid extraction technique using solvents of different polarity was employed to obtain extracts with different chemical composition from the inactive dry yeast preparations. Each of the extracts was assayed against the three lactic acid bacteria. Important differences in the effect of the extracts on the growth of the bacteria were observed, which depended on the solvent employed during the extraction, on the type of commercial preparations and on the lactic acid bacteria species. The extracts that exhibited the most different activity were chemically characterized in amino acids, free monosaccharides, monosaccharides from polysaccharides, fatty acids and volatile compounds. In general, specific amino acids and monosaccharides were related to a stimulating effect whereas fatty acid composition and likely some volatile compounds seemed to show an inhibitory effect on the growth of the lactic acid bacteria. These results may provide novel and useful information in trying to obtain better and more specific formulations of winemaking inactive dry yeast preparations.

Beneficial effects of probiotic and food borne yeasts on human health

Besides being important in the fermentation of foods and beverages, yeasts have shown numerous beneficial effects on human health. Among these, probiotic effects are the most well known health effects including prevention and treatment of intestinal diseases and immunomodulatory effects. Other beneficial functions of yeasts are improvement of bioavailability of minerals through the hydrolysis of phytate, folate biofortification and detoxification of mycotoxins due to surface binding to the yeast cell wall.