270 research outputs found
An important step forward for the future development of an easy and fast procedure for identifying the most dangerous wine spoilage yeast, Dekkera bruxellensis, in wine environment
Dekkera bruxellensis is the main reason for spoilage in the wine industry. It renders the products unacceptable leading to large economic losses. Fluorescence In Situ Hybridisation (FISH) technique has the potential for allowing its specific detection. Nevertheless, some experimental difficulties can be encountered when FISH technique is applied in the wine environment (e.g. matrix and cells autofluorescence, fluorophore inadequate selection and probes low specificity to the target organisms). An easy and fast in-suspension RNA-FISH procedure was applied for the first time for identifying D. bruxellensis in wine. A previously designed RNA-FISH probe to detect D. bruxellensis (26S D. brux.5.1) was used and the matrix and cells fluorescence interferences, the influence of three fluorophores in FISH performance and the probe specificity were evaluated. The results revealed that to apply RNA-FISH technique in the wine environment a red-emitting fluorophore should be used. Good probe performance and specificity was achieved with 25% of formamide. The resulting RNA-FISH protocol was applied in wine samples artificially inoculated with D. bruxellensis. This spoilage microorganism was detected in wine at cell densities lower than those associated with phenolic off-flavours.
Thus, the RNA-FISH procedure described in this work represents an advancement to facilitate early detection of the most dangerous wine spoilage yeast and, consequently, to reduce the economic losses caused by this yeast to the wine industry.This work was co-financed by Foundation for Science and Technology (FCT) and the European Union through the European Regional Development Fund ALENTEJO 2020 through the projects PTDC/BBB-IMG/0046/2014 and ALT20-03-0145-FEDER-000015, respectively. Marina González-Pérez acknowledges FCT for the economic support through the post-doctoral grant SFRH/BPD/100754/2014
Tracking the origin and divergence of cholinesterases and neuroligins: the evolution of synaptic proteins
14. International Symposium on Cholinergic Mechanisms (ISCM), Hangzhou, 2013/05/05-9A cholinesterase activity can be found in all kingdoms of living organism, yet cholinesterases involved in cholinergic transmission appeared only recently in the animal phylum. Among various proteins homologous to cholinesterases, one finds neuroligins. These proteins, with an altered catalytic triad and no known hydrolytic activity, display well-identified cell adhesion properties. The availability of complete genomes of a few metazoans provides opportunities to evaluate when these two protein families emerged during evolution. In bilaterian animals, acetylcholinesterase co-localizes with proteins of cholinergic synapses while neuroligins co-localize and may interact with proteins of excitatory glutamatergic or inhibitory GABAergic/glycinergic synapses. To compare evolution of the cholinesterases and neuroligins with other proteins involved in the architecture and functioning of synapses, we devised a method to search for orthologs of these partners in genomes of model organisms representing distinct stages of metazoan evolution. Our data point to a progressive recruitment of synaptic components during evolution. This finding may shed light on the common or divergent developmental regulation events involved into the setting and maintenance of the cholinergic versus glutamatergic and GABAergic/glycinergic synapses
Use of superheated liquids for the extraction of non-volatile compounds from wood: HPLC studies
A study of the extraction of oak wood compounds using superheated water-ethanol mixtures ranging from 10 to 60% ethanol is reported. Identification and characterization of the extracted compounds have been made by high performance liquid chromatography. The extraction has been performed using the static mode by single or repetitive cycles. The variables affecting the extraction process have been studied and their optimum values established (extraction time: 50 min; pressure: 40 atm; extraction temperature: 180º C). The study allows to compare the non-volatile polyphenol fractions obtained in this way with those present in commercial samples with fully agreement between them. In addition, the method allows manipulation of the extract composition by changing the working pressure, temperature and water-ethanol ratio
ESTHER, the database of the α/β-hydrolase fold superfamily of proteins: tools to explore diversity of functions
The ESTHER database, which is freely available via a web server (http://bioweb.ensam.inra.fr/esther) and is widely used, is dedicated to proteins with an a/b-hydrolase fold, and it currently contains >30 000 manually curated proteins. Herein, we report those substantial changes towards improvement that we have made to improve ESTHER during the past 8 years since our 2004 update. In particular, we generated 87 new families and increased the coverage of the UniProt Knowledgebase (UniProtKB). We also renewed the ESTHER website and added new visualization tools, such as the Overall Table and the Family Tree. We also address two topics of particular interest to the ESTHER users. First, we explain how the different enzyme classifications (bacterial lipases, peptidases,carboxylesterases) used by different communities of users are combined in ESTHER. Second, we discuss how variations of core architecture or in predicted active site residues result in a more precise clustering of families, and whether this strategy provides trustable hints to identify enzymelike proteins with no catalytic activity
Influence of phenolic acids on growth and inactivation of Oenococcus oeni and Lactobacillus hilgardii
Aims: To determine the effect of several wine-associated, phenolic acids on the growth and viability of strains of
Oenococcus oeni and Lactobacillus hilgardii.
Methods and Results: Growth was monitored in ethanol-containing medium supplemented with varying
concentrations of hydroxybenzoic acids (p-hydroxybenzoic, protocatechuic, gallic, vanillic and syringic acids) and
hydroxycinnamic acids (p-coumaric, caffeic and ferulic acids). Progressive inactivation was monitored in ethanolcontaining
phosphate buffer supplemented in a similar manner to the growth experiments. Hydroxycinnamic acids
proved to be more inhibitory to the growth of O. oeni than hydroxybenzoic acids. On the other hand, some acids
showed a beneficial effect on growth of Lact. hilgardii. p-Coumaric acid showed the strongest inhibitory effect on
growth and survival of both bacteria.
Conclusions: Most phenolic acids had a negative effect on growth of O. oeni, for Lact. hilgardii this effect was only
noted for p-coumaric acid. Generally, O. oeni was more sensitive to phenolic acid inactivation than Lact. hilgardii.
Significance and Impact of the Study: Eight wine-derived, phenolic acids were compared for their effects on
wine lactic acid bacteria. Results indicate that phenolic acids have the capacity to influence growth and survival
parameters. The differences found between phenolic compounds could be related to their different chemical
structures
Method for analysis of heavy sulphur compounds using gas chromatography with flame photometric detection
A method for analysis of heavy sulphur compounds in wines, based on gas chromatography (GC) with flame photometric detection, is
reported. Wine samples preparation includes a dichloromethane liquid–liquid extraction followed by concentration under a nitrogen atmosphere.
The extracted fraction was also analysed by GC–mass spectrometry. The method enables high recovery of sulphur compounds in wine
and satisfies the requirements of repeatability and sensitivity. Applications of the method to red, white and Port wines are reported
Yeasts and wine off-flavours: a technological perspective
Review article. Part of the special issue "Wine microbiology and safety: from the vineyard to the bottle (Microsafety Wine)", 19-20 Nov. 2009, ItalyIn wine production, yeasts have both beneficial
and detrimental activities. Saccharomyces cerevisiae is the
yeast mainly responsible for turning grape juice into wine
but this species and several others may also show
undesirable effects in wines. Among such effects, technologists
are particularly concerned with the production of offflavours
that may occur during all stages of winemaking.
Typical spoiling activities include the production of ethyl
acetate by apiculate yeasts before fermentation, hydrogen
sulphide by S. cerevisiae during fermentation phases,
acetaldehyde by film-forming yeasts during bulk storage,
and volatile phenols by Dekkera bruxellensis during storage
or after bottling. The occurrence of these hazards depends
on the technological operations designed to obtain a given
type of wine and most can be avoided by current preventive
or curative measures. On the contrary, good manufacturing
practices must be strengthened to deal with the problem of
volatile phenol production in red wines. Appropriate
monitoring of D. bruxellensis populations and quantification
of 4-ethylphenol is advised during storage, particularly
when oak barrels are used, and absence of viable cells must
be guaranteed in bottled wines. This work, which is based
on our experience at winery level, aims to provide
information on appropriate technological strategies to deal
with the problem of off-flavours produced by yeasts
Oenological characterisation of indigenous strains of S. cerevisiae isolated in a biodynamic winery in the Cortona DOC area
Genotypic and technological characterisation of the S. cerevisiae population isolated in a biodynamic winery in the Cortona DOC area was performed to gain better knowledge of the variables that influence winemaking. The oenological performance of 11 S. cerevisiae strains was evaluated with physiological tests; strain typing was performed through analysis of interdelta sequences and 26S rDNA sequencing. The analysis revealed a remarkable variability in terms of S. cerevisiae strains, despite the homogeneity of wine features, underlining the high levels of biodiversity characterising biodynamic agriculture. Some strains were found in wines of different vintages, suggesting the presence of an established microbiota in the winery. Oenological tests demonstrated that while some yeasts provided reliable oenological performance, other strains were not able to accomplish prompt and effective alcoholic fermentation, or were characterised by spoilage characteristics, such as excessive production of volatile phenols or acetic acid. Indigenous strains of S. cerevisiae could be a useful instrument for reliable winemaking without altering the native microbiota of each oenological environment. However, characterisation of their oenological suitability, and the application of practices able to drive the evolution of microbiota, must be employed to reduce the risk of wine spoilage
Effect of kaolin silver complex on the control of populations of Brettanomyces and acetic acid bacteria in wine
In this work, the effects of kaolin silver complex
(KAgC) have been evaluated to replace the use of SO2 for
the control of spoilage microorganisms in the winemaking
process. The results showed that KAgC at a dose of 1 g/L
provided effective control against the development of B.
bruxellensis and acetic acid bacteria. In wines artificially
contaminated with an initial population of B. bruxellensis
at 104 CFU/mL, a concentration proven to produce off
flavors in wine, only residual populations of the contaminating yeast remained after 24 days of contact with the
additive. Populations of acetic bacteria inoculated into
wine at concentrations of 102 and 104 CFU/mL were
reduced to negligible levels after 72 h of treatment with
KAgC. The antimicrobial effect of KAgC against B.
bruxellensis and acetic bacteria was also demonstrated in a
wine naturally contaminated by these microorganisms,
decreasing their population in a similar way to a chitosan
treatment. Related to this effect, wines with KAgC showed
lower concentrations of acetic acid and 4-ethyl phenol than
wines without KAgC. The silver concentration from KAgC
that remained in the finished wines was below the legal
limits. These results demonstrated the effectiveness of
KAgC to reduce spoilage microorganisms in winemaking.info:eu-repo/semantics/acceptedVersio
Impact of volatile phenols and their precursors on wine quality and control measures of Brettanomyces/Dekkera yeasts
Volatile phenols are aromatic compounds and one of the key molecules responsible for olfactory defects in wine. The yeast genus Brettanomyces is the only major microorganism that has the ability to covert hydroxycinnamic acids into important levels of these compounds, especially 4-ethylphenol and 4-ethylguaiacol, in red wine. When 4-ethylphenols reach concentrations greater than the sensory threshold, all wine’s organoleptic characteristics might be influenced or damaged. The aim of this literature review is to provide a better understanding of the physicochemical, biochemical, and metabolic factors that are related to the levels of p-coumaric acid and volatile phenols in wine. Then, this work summarizes the different methods used for controlling the presence of Brettanomyces in wine and the production of ethylphenols
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