Biovalorization of spent Konacha tea leaves via single-culture fermentation involving wine yeasts and lactic acid bacteria.

AIMS: The objective of this study was to explore the potential of fermentation as a biovalorization strategy for spent tea leaves (STL), a major agrifood waste generated from the tea extraction industry. Fermentation by wine yeasts or lactic acid bacteria (LAB) has shown promising results in previous studies across various substrates. METHODS AND RESULTS: Konacha (green tea) STL slurries were inoculated with single strains of wine yeasts or LAB respectively. After a 48-h fermentation, changes in selected nonvolatile and volatile compositions were evaluated. Fermentation by LAB increased organic acid content by 5- to 7-fold (except Lactobacillus fermentum) and modulated the composition of major tea catechins, whereas wine yeast fermentation resulted in a 30% increase in amino acid content. Strain-specific production of specific volatile compounds was also observed such as butanoic acid (L. fermentum), isoamyl acetate (Pichia kluyveri) and 4-ethylphenol (L. plantarum). CONCLUSIONS: Both volatile and nonvolatile compound compositions of Konacha STL were successfully modified via wine yeast and LAB fermentation. SIGNIFICANCE AND IMPACT OF STUDY: Our findings indicate that Konacha STL is a suitable medium for biovalorization by wine yeasts or LAB via the generation of commercially useful volatile and nonvolatile compounds. Future optimizations could further render fermentation an economically viable strategy for the upcycling of STL.

Comparative uptake of exogenous thiamine and subsequent metabolic footprint in Saccharomyces cerevisiae and Kluyveromyces marxianus under simulated oenological conditions.

Managed inoculation of non-Saccharomyces yeast species is regarded as a practical way to introduce new characteristics to wine. However, these yeasts struggle to survive until fermentation is complete. Kluyveromyces marxianus IWBT Y885 is one such yeast. Although it displays interesting oenological properties, a longer persistence during alcoholic fermentation would warranty a stronger impact on wine composition. A key factor for survival, growth and sustained metabolic activity of all yeasts is their nutrient requirements. Thus, identifying nutrients that are essential for maximising fermentation performance, and subsequently ensuring adequate levels of nutrients, is a means to ensure significant contribution of yeasts to wine properties. This study aimed to identify essential nutrients, other than previously studied sugars and nitrogen, for maximum impact of K. marxianus Y885, as well as to characterise the outcomes of their utilisation. A multifactorial experimental design was employed to investigate the impact of nutrient concentrations on fermentation performance with K. marxianus Y885 in synthetic must. B-complex vitamins most significantly impacted fermentation performance of K. marxianus Y885 compared to other nutrient groups investigated. Considering the well-established role of the vitamin, thiamine, for maximum fermentation performance during winemaking and the fact that it may be supplemented to wine fermentations legally, the responses to specifically exogenous thiamine concentration for K. marxianus Y885 and Saccharomyces cerevisiae EC1118 were compared in terms of population viability, fermentation rate, total sugars utilised, thiamine assimilation kinetics, and final wine composition. A saturation effect for initial thiamine concentration of K. marxianus Y885 fermentations was characterised, with a maximum fermentation rate and over 90% of available sugars utilisation obtained at 0.25 mg/L. An appreciably larger comparative increase in exponential cell growth rate, maximum population, fermentation rate and total CO2 production for K. marxianus Y885 compared to S. cerevisiae EC1118 revealed a greater necessity for thiamine to ensure maximum fermentation performance. A delayed uptake of thiamine at higher concentrations for K. marxianus Y885 suggested differential regulation of thiamine uptake compared to S. cerevisiae EC1118. In addition, different trends in metabolites produced between species suggest that thiamine concentration impacts the carbon metabolic flux differently in these two yeasts, potentially impacting final wine properties.

Evaluation of proximate composition, flavonoids, and antioxidant capacity of ginkgo seeds fermented with different rice wine starters.

Ginkgo seeds are distinguished as source of highly promising food and traditional Chinese herbal for thousands of years. It is well known for the significant curative effects on some diseases, such as cough and asthma. The current work aimed to study the proximate composition, phytochemical content, and antioxidant capacity of ginkgo seeds fermented by 17 varieties of rice wine starters. Solid state fermentation was used to improve the nutrition of ginkgo seeds. Correlation analysis showed that there was a significant correlation between the flavonoids, approximate composition, and antioxidant activity in fermented ginkgo seeds. Through principal component analysis (PCA), Yp rice wine starter was found as the most suitable for ginkgo seeds fermentation. After fermentation of Yp rice wine starter, the content of quercetin increased by 188.1%, the content of reducing sugars and peptides increased by 16 and 24 times, respectively, and the scavenging ability of 1,1-diphenyl-2-picrylhydrazyl free radicals increased from 4.69 to 12.43 mg TE/g. The solid-state fermentation of ginkgo seeds could be efficiently applied to food industrial production, and fermentation significantly increased the antioxidant activity and flavonoid content of ginkgo seeds, as well as improved their nutrition. PRACTICAL APPLICATION: Traditionally, rice wine starter was used for brewing wine, only some folk use rice wine starter for food production. In this paper, ginkgo seeds are selected for fermentation, which not only solves the problem of ginkgo seeds surplus, but also provides a reliable technical route for industry. It provides reference for the application of rice wine starter in food in the future.

Transcriptome analysis reveals the protection mechanism of proanthocyanidins for Saccharomyces cerevisiae during wine fermentation.

Grape-derived proanthocyanidins could act as a protector against various environmental stresses for Saccharomyces cerevisiae during wine fermentation, resulting in the increased physiological activity, fermentation efficiency and improved wine quality. In order to explore the possible protection mechanism of proanthocyanidins globally, RNA-seq analysis for wine yeast AWRI R2 cultivated with 0 g/L (group A), 0.1 g/L (group B), 1.0 g/L (group C) proanthocyanidins were applied in this study. Differentially expressed genes were enriched into six metabolic pathways including vitamin B6, thiamine, amino acids, aminoacyl-tRNA, carbohydrate and steroid based on KEGG enrichment analysis. Four key genes (SNZ2, THI6, THI21 and THI80), participated in the biosynthesis of vitamin B6 and thiamine, were up-regulated significantly in proanthocyanidins treated yeast cells and the gene expression levels were verified by RT-qPCR. Yeast cells supplemented with proanthocyanidins performed increased intracellular levels of vitamin B6 and thiamine and higher cell viability compared to the control group. In addition, the composition of intracellular fatty acids showed an obvious alternation in proanthocyanidins-treated yeast cells, in which the UFAs content increased whereas the SFA content decreased. In general, we provided an indirect protection effect of proanthocyanidins on the yeast cells to alleviate environmental stresses during wine fermentation.

Use of Multiflora Bee Pollen as a Flor Velum Yeast Growth Activator in Biological Aging Wines.

Flor velum yeast growth activators during biological aging are currently unknown. In this sense, this research focuses on the use of bee pollen as a flor velum activator. Bee pollen influence on viable yeast development, surface hydrophobicity, and yeast assimilable nitrogen has already been studied. Additionally, bee pollen effects on the main compounds related to flor yeast metabolism and wine sensory characteristics have been evaluated. "Fino" (Sherry) wine was supplemented with bee pollen using six different doses ranging from 0.1 to 20 g/L. Its addition in a dose equal or greater than 0.25 g/L can be an effective flor velum activator, increasing yeast populations and its buoyancy due to its content of yeast assimilable nitrogen and fatty acids. Except for the 20 g/L dose, pollen did not induce any significant effect on flor velum metabolism, physicochemical parameters, organic acids, major volatile compounds, or glycerol. Sensory analysis showed that low bee pollen doses increase wine's biological aging attributes, obtaining the highest score from the tasting panel. Multiflora bee pollen could be a natural oenological tool to enhance flor velum development and wine sensory qualities. This study confirms association between the bee pollen dose applied and the flor velum growth rate. The addition of bee pollen could help winemakers to accelerate or reimplant flor velum in biologically aged wines.

Transcriptomic and proteomic effects of (-)-epigallocatechin 3-O-(3-O-methyl) gallate (EGCG3"Me) treatment on ethanol-stressed Saccharomyces cerevisiae cells.

Saccharomyces cerevisiae (S. cerevisiae) is the main fermentation strain in brewing industry. However, the accumulation of ethanol during the fermentation inhibits the growth of S. cerevisiae. Polyphenols are important bioactive ingredients in oolong tea, and epigallocatechin-3-O-(3"-O-methyl)-gallate (EGCG3"Me) has exhibited ameliorate effect on alcohol intoxication. Therefore, in the current work, we used RNA-seq transcriptomics and iTRAQ proteomic analysis to study the effect of EGCG3"Me on ethanol-stressed S. cerevisiae. After EGCG3"Me intervention (0.8%, w/v), 178 up-regulated and 172 down-regulated genes were identified, meanwhile, 190 differentially expressed proteins (DEPs) were identified. In addition, KEGG pathways for metabolic pathways, biosynthesis of secondary metabolites and microbial metabolism were among the most DEPs after EGCG3"Me intervention. The integrated transcriptomic and proteomic analysis indicated EGCG3"Me may alleviate ethanol-induced damage on the cell wall and cell membrane of S. cerevisiae, and facilitate the redox balance and glycolysis. This study provides new insights into the mechanisms underlying the molecular response to ethanol in S. cerevisiae by the treatment of EGCG3"Me.

The changes of microbial community and flavor compound in the fermentation process of Chinese rice wine using Fagopyrum tataricum grain as feedstock.

Chinese rice wine (CRW), a unique wine species, has a long history in China. Fagopyrum tataricum grain is a kind of high-quality grain with function in health care. The production of CRW wine with F. tataricum grain is beneficial to the development of new rice wine products. The flavor compounds and microorganisms in F. tataricum grain rice wine were studied. One hundred and seven volatile compounds (including 11 kinds of pyrazines that were rarely detected in wine) were detected and eight organic acids were measured. The microecological diversity in the fermentation process of F. tataricum rice wine was studied. It was found that Bacillus was the main bacterial genus, and the unclassfied_O_Saccharomycetales was the main fungi. Correlation analysis between microorganism and flavor compound shown there are 838 correlations. A total of 108 microbial genera maybe participate in the formation of flavor compounds. In addition, fourteen genera included unclassified_O_Saccharomycetales, Lactococcus, Pediococcus, Aspergillus, Cladosporium, Cochliobolus, Sporidiobolus, Pichia and Saccharomycopsis et al. were screened as functional significant microbiota and built correlation with flavor compounds. This work provides a perspective for bridging the gap between flavor compound and microbial community, and advances our understanding of mechanisms in F. tataricum rice wine fermentation.

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

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

The utilisation of nitrogenous compounds by commercial non-Saccharomyces yeasts associated with wine.

Commercial wine fermentation is commonly conducted by inoculated strains of Saccharomyces cerevisiae. However, other non-Saccharomyces yeast species have recently become popular co-inoculants. Co-inoculated yeast species compete with each other for nutrients, and such competition may impact fermentation kinetics and aroma production. Understanding the specific nutrient requirements of non-Saccharomyces strains therefore is essential to better characterize the competitive potential of each strain, and to support rational decision making for nutrient supplementation during wine making. This study investigated the nitrogen source preference of commercial non-Saccharomyces yeasts by conducting pure culture and sequential culture fermentations in synthetic grape musts with adjusted nitrogen contents. Amino acid and ammonium uptake varied between yeast species. Lachancea thermotolerans and Torulaspora delbrueckii assimilated more nitrogen at a faster rate than Pichia kluyveri and Metschnikowia pulcherrima. Significant variation in amino acid preference between species was observed. Sequential fermentations confirmed the more competitive behaviour of L. thermotolerans and T. delbrueckii, with consequences for fermentation kinetics and aroma production. Furthermore, the data suggest that declining populations of non-Saccharomyces yeasts release nitrogen and supports the activity of S. cerevisiae. The data provide the most detailed assessment of nitrogen utilisation by the investigated yeast strains in a wine environment.

Effects of selenium on oxidative damage and antioxidant enzymes of eukaryotic cells: wine Saccharomyces cerevisiae.

AIM: To clarify the effects of selenium (Se), parameters related to oxidative issues, as well as the antioxidant response were investigated on an autochthonous wine yeast strain. METHODS AND RESULTS: Antioxidant enzyme activity, gel electrophoresis, Western blot and MDA level were used to investigate the effects of different concentration of Se in wine yeast. We found that Se is able to affect the enzymatic activities of catalase (CAT), glutathione peroxidase (GPx) and superoxide dismutase (SOD). An increase in lipid peroxidation was observed in a dose-dependent manner of (Se), thus, indicating the occurrence of cell membrane damage. Additionally, Se induced post-translational oxidative modifications of proteins, especially oxidation of thiol groups (both reversible and irreversible) and protein carbonylation (irreversible oxidation). CONCLUSION: These results obtained could further the understanding the effect of different concentration of Se in wine yeast strain with which Se affect the enzymatic activities and induces some post-translational modifications of proteins. SIGNIFICANCE AND IMPACT OF THE STUDY: The understanding of mechanisms regulating the response of wine yeast to Se is important for future work using selenized yeast as enriched Se supplements in human nutrition.

Ozone Treatment of Grapes During Withering for Amarone Wine: A Multimodal Imaging and Spectroscopic Analysis.

The production of Amarone wine is governed by a disciplinary guideline to preserve its typical features; however, postharvest infections by the fungus Botrytis cinerea (B. cinerea) not only represent a phytosanitary problem but also cause a significant loss of product. In this study, we tested a treatment with mild ozoniztion on grapes for Amarone wine production during withering in the fruttaio (the environment imposed by the disciplinary guideline) and evaluated the impact on berry features by a multimodal imaging approach. The results indicate that short and repeated treatments with low O3 concentrations speed up the naturally occurring berry withering, probably inducing a reorganization of the epicuticular wax layer, and inhibit the development of B. cinerea, blocking the fungus in an intermediate vegetative stage. This pilot study will pave the way to long-term research on Amarone wine obtained from O3-treated grapes.

Use of a wine yeast deletion collection reveals genes that influence fermentation performance under low-nitrogen conditions.

A deficiency of nitrogenous nutrients in grape juice can cause stuck and sluggish alcoholic fermentation, which has long been a problem in winemaking. Nitrogen requirements vary between wine yeast strains, and the ability of yeast to assimilate nitrogen depends on the nature and concentration of nitrogen present in the medium. In this study, a wine yeast gene deletion collection (1844 deletants in the haploid AWRI1631 background) was screened to identify genes whose deletion resulted in a reduction in the time taken to utilise all sugars when grown in a chemically defined grape juice medium supplemented with limited nitrogen (75 mg L-1 as a free amino acid mixture). Through micro-scale and laboratory-scale fermentations, 15 deletants were identified that completed fermentation in a shorter time than the wildtype (c.a. 15%-59% time reduction). This group of genes was annotated to biological processes including protein modification, transport, metabolism and ubiquitination (UBC13, MMS2, UBP7, UBI4, BRO1, TPK2, EAR1, MRP17, MFA2 and MVB12), signalling (MFA2) and amino acid metabolism (AAT2). Deletion of MFA2, encoding mating factor-a, resulted in a 55% decrease in fermentation duration. Mfa2Δ was chosen for further investigation to understand how this gene deletion conferred fermentation efficiency in limited nitrogen conditions.

Spent yeast as natural source of functional food additives

Spent yeasts are by-products arising from beer and wine production which over many years have been chiefly used as feed additives for livestock. They contain many valuable and bioactive substances which has thereby generated much interest in their exploitation. Up till now, the main products obtained from beer-brewing yeasts are ß-glucans and yeast extracts. Other like foodstuffs include dried brewer's yeast, where this is dried and the bitterness removed to be fit for human consumption as well as mannan-oligosaccharides hitherto used in the feed industry. ß-glucans constitute the building blocks of yeast cell walls and can thus be used in human nutrition as dietary supplements or serving as food additives in functional foods. ß-glucans products obtained via post-fermentation of beer also exhibit a high and multi-faceted biological activity where they improve the blood's lipid profile, enhance immunological status and have both prebiotic and anti-oxidant properties. Yeast extracts are currently being used more and more to enhance flavour in foodstuffs, particularly for meat and its products. Depending on how autolysis is carried out, it is possible to design extracts of various meat flavours characteristic of specific meats. Many different flavour profiles can be created which may be additionally increased in combination with vegetable extracts. Within the food market, yeast extracts can appear in various guises such as liquids, pastes or powders. They all contain significant amounts of glutamic acid, 5'-GMP and 5'-IMP nucleotides together with various amino acids and peptides that act synergistically for enhancing the flavour of foodstuff products. Recent studies have demonstrated additional benefits of yeast extracts as valuable sources of amino acids and peptides which can be used in functional foods and dietary supplements. These products possess GRAS status (Generally Recognised As Safe) which thereby also adds further as to why they should be used as natural food additives that are functional.

The effect of linoleic acid on the Sauvignon blanc fermentation by different wine yeast strains.

The level of linoleic acid in the Sauvignon blanc (SB) grape juice affects the development of different aroma compounds during fermentation by Saccharomyces cerevisiae EC1118, including key varietal thiols such as 3-mercaptohexanol (3MH) and 3-mercaptohexyl acetate (3MHA). However, it is still unknown if linoleic acid would affect in a similar way other commonly used S. cerevisiae wine strains. Here we investigated the effect of grape juice linoleic acid on the development of aroma compounds and other metabolites of SB wines using different wine yeast strains: EC1118, AWRI796 and VIN13. Linoleic acid clearly affected the levels of acetylated aroma compounds, several amino acids, and antioxidant molecules, independent of yeast strain, but the production of 3MH was affected by linoleic acid in a strain-specific manner. Moreover, the supplementation of deuterium-labelled 3MH also affected the production of varietal thiols in a strain-specific way. Linoleic acid reduced the acetylation process probably by inhibiting an acetyltransferase, an effect that was independent of the yeast strain. However, regulation of the 3MH biosynthesis is strain-specific, which suggests a mindful consideration not only towards the wine yeast but also to the linoleic acid concentration in the grape juice in order to obtain the desired wine aroma characteristics.

Nutrient depletion modifies cell wall adsorption activity of wine yeast.

Yeast cell wall is a structure that helps yeasts to manage and respond to many environmental stresses. The mannosylphosphorylation is a modification in response to stress that provides the cell wall with negative charges able to bind compounds present in the environment. Phenotypes related to the cell wall modification such as the filamentous growth in Saccharomyces cerevisiae are affected by nutrient depletion. The present work aimed at describing the effect of carbon and/or nitrogen limitation on the aptitude of S. cerevisiae strains to bind coloured polyphenols. Carbon- and nitrogen-rich or deficient media supplemented with grape polyphenols were used to simulate different grape juice conditions-early, mid, 'adjusted' for nitrogen, and late fermentations. In early fermentation condition, the R+G+B values range from 106 (high adsorption, strain Sc1128) to 192 (low adsorption, strain Σ1278b), in mid-fermentation the values range from 111 (high adsorption, strain Sc1321) to 258 (low adsorption, strain Sc2306), in 'adjusted' for nitrogen conditions the values range from 105 (high adsorption, strain Sc1321) to 194 (low adsorption, strain Sc2306) while in late fermentation conditions the values range from 101 (high adsorption, strain Sc384) to 293 (low adsorption, strain Sc2306). The effect of nutrient availability is not univocal for all the strains and the different media tested modified the strains behaviour. In all the media the strains show significant differences. Results demonstrate that wine yeasts decrease/increase their parietal adsorption activity according to the nutrient availability. The wide range of strain variability observed could be useful in selecting wine starters.

Effect of yeast strain and some nutritional factors on tannin composition and potential astringency of model wines.

Nine Saccharomyces cerevisiae cultures, isolated from different sources, were tested for their ability to reduce tannins reactive towards salivary proteins, and potentially responsible for wine astringency. Strains were preliminary genetically characterized and evaluated for physiological features of technological interest. Laboratory-scale fermentations were performed in three synthetic media: CT) containing enological grape tannin; CTP) CT supplemented with organic nitrogen sources; CTPV) CTP supplemented with vitamins. Adsorption of total tannins, tannins reactive towards salivary proteins, yellow pigments, phenolics having antioxidant activity, and total phenols, characterizing the enological tannin, was determined by spectrophotometric methods after fermentation. The presence of vitamins and peptones in musts greatly influenced the adsorption of tannins reactive towards salivary proteins (4.24 g/L gallic acid equivalent), thus promoting the reduction of the potential astringency of model wines. With reference to the different phenolic classes, yeast strains showed different adsorption abilities. From a technological point of view, the yeast choice proved to be crucial in determining changes in gustative and mouthfeel profile of red wines and may assist winemakers to modulate colour and astringency of wine.

Evaluation of the oenological suitability of grapes grown using biodynamic agriculture: the case of a bad vintage.

AIMS: We compare the evolution of the microbiota of grapes grown following conventional or biodynamic protocols during the final stage of ripening and wine fermentation in a year characterized by adverse climatic conditions. METHODS AND RESULTS: The observations were made in a vineyard subdivided into two parts, cultivated using a biodynamic and traditional approach in a year which saw a combination of adverse events in terms of weather, creating the conditions for extensive proliferation of vine pests. The biodynamic approach was severely tested, as agrochemicals were not used and vine pests were counteracted with moderate use of copper, sulphur and plant extracts and with intensive use of agronomical practices aimed at improving the health of the vines. Agronomic, microbiological and chemical testing showed that the response of the vineyard cultivated using a biodynamic approach was comparable or better to that of vines cultivated using the conventional method. CONCLUSIONS: The work suggests that biodynamic cultivation of the grapevine may be sustainable even in difficult conditions, representing an interesting alternative to traditional vine-growing approaches. SIGNIFICANCE AND IMPACT OF THE STUDY: This theme is topical and of interest to winemakers and consumers today, but is not easy to study due to the difficulties in finding vineyards with homogeneous characteristics, cultivated using different agronomical protocols. The particular climatic conditions observed in 2014 made this year a rare model, making it possible to verify the applicability of biodynamics to vine growing. The strict experimental plan gave results particularly useful for understanding the features of grape microbiota in a biodynamic context.

Effect of selenium on growth and antioxidant enzyme activities of wine related yeasts.

The use of supplements in the diet is a common practice to address nutritional deficiencies. Selenium is an essential micronutrient with an antioxidant and anti-carcinogenic role in human and animal health. There is increasing interest in developing nutritional supplements such as yeast cells enriched with selenium. The possibility of producing beverages, namely wine, with selenium-enriched yeasts, led us to investigate the selenium tolerance of six wine related yeasts. The production of such cells may hamper selenium toxicity problems. Above certain concentrations selenium can be toxic inducing oxidative stress and yeast species can show different tolerance. This work aimed at studying selenium tolerance of a diversity of wine related yeasts, thus antioxidant response mechanisms with different concentrations of sodium selenite were evaluated. Viability assays demonstrated that the yeast Torulaspora delbrueckii showed the highest tolerance for the tested levels of 100 µg mL(-1) of sodium selenite. The evaluation of antioxidative enzyme activities showed the best performance for concentrations of 250 and 100 µg mL(-1), respectively for the yeast species Saccharomyces cerevisiae and Hanseniaspora guilliermondii. These results encourage future studies on the possibility to use pre-enriched yeast cells as selenium supplement in wine production.

Characterization of pectinase activity for enology from yeasts occurring in Argentine Bonarda grape.

Pectinolytic enzymes are greatly important in winemaking due to their ability to degrade pectic polymers from grape, contributing to enhance process efficiency and wine quality. This study aimed to analyze the occurrence of pectinolytic yeasts during spontaneous fermentation of Argentine Bonarda grape, to select yeasts that produce extracellular pectinases and to characterize their pectinolytic activity under wine-like conditions. Isolated yeasts were grouped using PCR-DGGE and identified by partial sequencing of 26S rRNA gene. Isolates comprised 7 genera, with Aureobasidium pullulans as the most predominant pectinolytic species, followed by Rhodotorula dairenensis and Cryptococcus saitoi. No pectinolytic activity was detected among ascomycetous yeasts isolated on grapes and during fermentation, suggesting a low occurrence of pectinolytic yeast species in wine fermentation ecosystem. This is the first study reporting R. dairenensis and Cr. saitoi species with pectinolytic activity. R. dairenensis GM-15 produced pectinases that proved to be highly active at grape pH, at 12 °C, and under ethanol and SO2 concentrations usually found in vinifications (pectinase activity around 1.1 U/mL). This strain also produced cellulase activity at 12 °C and pH 3.5, but did not produce ß-glucosidase activity under these conditions. The strain showed encouraging enological properties for its potential use in low-temperature winemaking.

Ochratoxin A Dietary Exposure of Ten Population Groups in the Czech Republic: Comparison with Data over the World.

Ochratoxin A is a nephrotoxic and renal carcinogenic mycotoxin and is a common contaminant of various food commodities. Eighty six kinds of foodstuffs (1032 food samples) were collected in 2011-2013. High-performance liquid chromatography with fluorescence detection was used for ochratoxin A determination. Limit of quantification of the method varied between 0.01-0.2 µg/kg depending on the food matrices. The most exposed population is children aged 4-6 years old. Globally for this group, the maximum ochratoxin A dietary exposure for "average consumer" was estimated at 3.3 ng/kg bw/day (lower bound, considering the analytical values below the limit of quantification as 0) and 3.9 ng/kg bw/day (middle bound, considering the analytical values below the limit of quantification as 1/2 limit of quantification). Important sources of exposure for this latter group include grain-based products, confectionery, meat products and fruit juice. The dietary intake for "high consumers" in the group 4-6 years old was estimated from grains and grain-based products at 19.8 ng/kg bw/day (middle bound), from tea at 12.0 ng/kg bw/day (middle bound) and from confectionery at 6.5 ng/kg bw/day (middle bound). For men aged 18-59 years old beer was the main contributor with an intake of 2.60 ng/kg bw/day ("high consumers", middle bound). Tea and grain-based products were identified to be the main contributors for dietary exposure in women aged 18-59 years old. Coffee and wine were identified as a higher contributor of the OTA intake in the population group of women aged 18-59 years old compared to the other population groups.