CNRS Oenologie Research Unit

Bordeaux, France

CNRS Oenologie Research Unit

Bordeaux, France
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Chira K.,CNRS Oenologie Research Unit | Chira K.,French National Institute for Agricultural Research | Teissedre P.-L.,CNRS Oenologie Research Unit | Teissedre P.-L.,French National Institute for Agricultural Research
Food Chemistry | Year: 2013

In Merlot wines the evolution of volatile and non-volatile (ellagitannins) compounds extracted from winewoods while being macerated for 12 months was studied. Seven types of winewoods subjected to different toasting methods were used. Different rates of extraction, depending mainly on wood compounds origin (toasting or naturally present in wood) and on the watering process during toasting, were observed, which were reflected in sensory differences. Globally, volatile phenols together with aldehydes, phenols and lactones showed an increase with increasing maceration time. Ellagitannins were extracted faster during the first 3 months; after 6 months an important decrease was observed. Wines with winewoods subjected to watering during toasting were lower in ellagitannins concentrations and demonstrated the greatest decrease of these compounds during maceration. Astringency and bitterness intensified with increasing ellagitannins. Lactones induced positive sweetness sensations, whereas furanic and guaiacol compounds influenced bitterness and astringency. Spicy and vanilla descriptors were related to eugenol, vanillin and other odorous chemicals. © 2013 Elsevier Ltd. All rights reserved.

Romano A.,Research and Innovation Center | Trip H.,University of Groningen | Lolkema J.S.,University of Groningen | Lucas P.M.,Research and Innovation Center | Lucas P.M.,CNRS Oenologie Research Unit
Journal of Bacteriology | Year: 2013

Lactic acid bacteria play a pivotal role in many food fermentations and sometimes represent a health threat due to the ability of some strains to produce biogenic amines that accumulate in foods and cause trouble following ingestion. These strains carry specific enzymatic systems catalyzing the uptake of amino acid precursors (e.g., ornithine and lysine), the decarboxylation inside the cell, and the release of the resulting biogenic amines (e.g., putrescine and cadaverine). This study aimed to identify the system involved in production of cadaverine from lysine, which has not been described to date for lactic acid bacteria. Strain Lactobacillus saerimneri 30a (formerly called Lactobacillus sp. 30a) produces both putrescine and cadaverine. The sequencing of its genome showed that the previously described ornithine decarboxylase gene was not associated with the gene encoding an ornithine/ putrescine exchanger as in other bacteria. A new hypothetical decarboxylation system was detected in the proximity of the ornithine decarboxylase gene. It consisted of two genes encoding a putative decarboxylase sharing sequence similarities with ornithine decarboxylases and a putative amino acid transporter resembling the ornithine/putrescine exchangers. The two decarboxylases were produced in Escherichia coli, purified, and characterized in vitro, whereas the transporter was heterologously expressed in Lactococcus lactis and functionally characterized in vivo. The overall data led to the conclusion that the two decarboxylases and the transporter form a three-component decarboxylation system, with the new decarboxylase being a specific lysine decarboxylase and the transporter catalyzing both lysine/cadaverine and ornithine/putrescine exchange. To our knowledge, this is an unprecedented observation of a bacterial three-component decarboxylation system © 2013, American Society for Microbiology.

Claisse O.,CNRS Oenologie Research Unit | Claisse O.,French National Institute for Agricultural Research | Lonvaud-Funel A.,CNRS Oenologie Research Unit
Food Microbiology | Year: 2014

Oenococcus oeni is responsible for the malolactic fermentation of wine. Genomic diversity has already been established in this species. In addition, winemakers usually report varying starter-culture efficiency. It is essential to monitor indigenous and selected strains in order to understand strain survival and development during the winemaking process. A previous article described a variable number of tandem repeats (VNTR) scheme, based on five polymorphic loci of the genome. VNTR typing of O.oeni was highly discriminating, faster, and more reliable than the PFGE or MLST methods. The objective of this study was to set up a faster protocol by multiplexing, taking advantage of the high performance of multicolor capillary electrophoresis. The primers were labeled with multiple fluorescent dyes. PCR conditions were adapted by multiplexing amplifications in two separate PCR mixtures for the five loci, both at the same annealing temperature. The resulting assay proved to be robust, accurate, fast and easy to perform. Thanks to this new protocol, all O.oeni strains used in the study were typed using the five tandem repeats (TR). As expected, the primers for the five TR loci were specific to O.oeni. The method was improved to analyze isolated and mixed colonies, as well as bacteria harvested from wine using fast technology for analysis of nucleic acids (FTA®) technology. Finally, predictive models were constructed, to predict phylogenetic relationships and associate bacterial strain resistance to freeze-drying with fragment length analysis (FLA) profiles and genotypic and phenotypic characters. © 2013 Elsevier Ltd.

Claisse O.,CNRS Oenologie Research Unit | Claisse O.,French National Institute for Agricultural Research | Lonvaud-Funel A.,CNRS Oenologie Research Unit | Lonvaud-Funel A.,French National Institute for Agricultural Research
Food Microbiology | Year: 2012

Oenococcus oeni is responsible for the malolactic fermentation of wine. Genomic diversity has already been established in this species. In addition, winemakers usually report varying starter culture efficiency. The monitoring of indigenous and selected strains is essential for understanding strain survival and implantation during the winemaking process. In this study, we report the development of the first typing scheme for O. oeni using multiple-locus variable number of tandem repeat analysis (VNTR). The discriminatory power of 14 out of 44 tandem repeat loci in the genome of the PSU-1 strain was initially evaluated with a test collection of 18 genotypically distinct starter strains. Then five VNTR loci, which can be easily scored with the technology used here, were identified and used to genotype a collection of 236 strains, previously classified by restriction endonuclease analysis-pulsed-field gel electrophoresis (REA-PFGE) and multilocus sequence typing (MLST) into 136 REA-PFGE types or 110 MLST types. The discriminatory power of VNTR (as determined by Simpson's index of discrimination) was higher than that of the other two methods, with 201 VNTR types. The targeted VNTR markers were found to be stable and did not change for the clones of the same strain deposited in a collection at intervals of several years. Strains isolated from the different wine producing areas or the products were assigned to phylogenetic groups and were statistically linked with the VNTR profiles. Another interesting observation was that the loci were found in sequences homologous to regions encoding for membrane-anchored proteins. © 2012 Elsevier Ltd.

Furiga A.,University Paul Sabatier | Roques C.,University Paul Sabatier | Badet C.,CNRS Oenologie Research Unit
Journal of Applied Microbiology | Year: 2014

Aims: To investigate the preventive effects of an original combination of a grape seed extract (GSE) with an amine fluoride (Fluorinol®) on dental plaque formation and oxidative damage caused by oral bacteria. Methods and Results: The antibacterial activity of the compounds was assessed using the broth macrodilution method, and their antiplaque activity was evaluated on a multispecies biofilm grown on saliva-coated hydroxyapatite discs. The effect on glucosyltransferases activity was analysed through reductions in the overall reaction and the quantity of insoluble glucan synthesized. The combination of 2000 μg ml-1 of GSE with 10·2 mg ml-1 of Fluorinol® significantly decreased the biofilm formation (up to 4·76 log10 of reduction) and inhibited by 97·4% the insoluble glucan synthesis by glucosyltransferases. The antioxidant activity of this combination, alone or incorporated into a formulated mouthwash (Eludril daily®), was determined using the Trolox equivalent antioxidant capacity assay (TEAC), and both showed significantly greater antioxidant capacity than vitamin C. Conclusions: The GSE/Fluorinol® combination showed both a significant antiplaque activity and an important antioxidant capacity in vitro, without any bactericidal effects. Significance and Impact of the Study: This is, to our knowledge, the first report on the properties of an original combination of a polyphenolic extract with amine fluoride that could be used for the prevention of oral diseases and oxidative damage associated. © 2013 The Society for Applied Microbiology.

Samot J.,University of Bordeaux Segalen | Badet C.,University of Bordeaux Segalen | Badet C.,CNRS Oenologie Research Unit
Anaerobe | Year: 2013

The aim of this study was to determine the probiotic potential of autochthonous oral lactobacilli. For this, 66 strains were screened for antibacterial activity against two cariogenic strains (Streptococcus mutans and Actinomyces viscosus) and two periodontopathogenic strains (Fusobacterium nucleatum and Porphyromonas gingivalis).The inhibitory activity was investigated with the agar overlay technique. Positive results led us to explore some mechanisms of action.The ability to produce H2O2 and the glycerol dehydratase gene were searched among all the strains. The gassericin A gene was checked among the Lactobacillus gasseri.All the tested strains inhibited S. mutans and A. viscosus; only one did not inhibited F. nucleatum and 52 strains inhibited slightly the growth of P. gingivalis. No inactivation of antibacterial activity was observed after treatment with proteinase K. The gene of the gassericin A was not found in any strain.Only one strain showed a 275-bp amplicon corresponding to the Glycerol Dehydratase gene. This strain has been identified by DNA 16S sequencing as a L. gasseri.Among the 66 tested strains, 7 produced hydrogen peroxide.Our findings suggest that in addition to the previous results, some of the autochthonous oral lactobacilli tested could be considered as suitable probiotics. © 2012 Elsevier Ltd.

Nikolantonaki M.,CNRS Oenologie Research Unit | Darriet P.,CNRS Oenologie Research Unit
Journal of Agricultural and Food Chemistry | Year: 2011

A number of Sauvignon blanc wines made from hard pressed juices in an inert atmosphere (nitrogen) or in contact with oxygen were identified as having heavy off-flavors to varying degrees. Samples were extracted and subjected to time-based HPLC fractionation. The fractions were assessed by a sensory panel and those with unpleasant, irritating, off-odors were re-extracted. The extracts evaluated by gas chromatography coupled with olfactometry revealed a number of odoriferous zones, including one with an off-odor similar to the one perceived in two HPLC fractions. The odor was less intense in fractions previously supplemented with copper sulfate, suggesting that the compound(s) responsible were possibly thiol-related. A selective thiols extraction protocol and the analysis of the extract by gas chromatography coupled with mass spectrometry identified a new potent thiol in these wines. The compound responsible for the odoriferous zone, ethyl 2-sulfanylacetate (1), had an odor reminiscent of baked beans and Fritillaria meleagris bulbs. Its perception threshold was determined and sensory studies using graduated supplementation in dry white wines demonstrated its contribution to the off-odor observed in dry white wines. © 2011 American Chemical Society.

Laforgue R.,CNRS Oenologie Research Unit | Lonvaud-Funel A.,CNRS Oenologie Research Unit
Food Microbiology | Year: 2012

Brettanomyces bruxellensis populations have been correlated with an increase in phenolic off-flavors in wine. The volatile phenols causing the olfactory defect result from the successive decarboxylation and reduction of hydroxycinnamic acids that are normal components of red wines. The growth of B. bruxellensis is preventable by adding sulfur dioxide (SO2), with variable effectiveness. Moreover, it was hypothesized that SO2 was responsible for the entry of B. bruxellensis into a viable but non-culturable (VBNC) state. The aim of this project was to investigate the effects of SO2 on the remaining enzyme activities of B. bruxellensis populations according to their viability and cultivability, focusing on the hydroxycinnamate decarboxylase enzyme, the first enzyme needed, rather than the metabolites produced. Enzyme activity was determined both in cell-free extracts and resting cells after various SO2 treatments in synthetic media. After slight sulfiting (around 50 mg/L total SO2), the yeasts had lost part of their enzyme activity but not their cultivability. At higher doses (at least 75 mg/L total SO2) the majority of yeasts had lost their cultivability but still retained part of their enzyme activity. These results suggested that non culturable cells retained some enzyme activity. © 2012 Elsevier Ltd.

Renault P.E.,CNRS Oenologie Research Unit | Renault P.E.,British Petroleum | Albertin W.,CNRS Oenologie Research Unit | Bely M.,CNRS Oenologie Research Unit
Applied Microbiology and Biotechnology | Year: 2013

Alcoholic fermentation of grape must is a complex process, involving several yeast genera and species. The early stages in fermentation are dominated by non-Saccharomyces yeasts that are gradually replaced by the Saccharomyces cerevisiae species, which takes over the fermentation. Quantitative studies have reported the influence of non-Saccharomyces yeast species on wine quality and evaluated their biotechnological interest. The industrial yeast market, which, until recently, exclusively focused on S. cerevisiae, now offers S. cerevisiae/non-Saccharomyces (including Torulaspora delbrueckii) multi-starters. The development of these new mixed industrial starters requires a better understanding of the interaction mechanisms between yeast populations in order to optimize the aromatic impact of the non-Saccharomyces yeast while ensuring complete alcoholic fermentation thanks to S. cerevisiae. For this purpose, a new double-compartment fermentor was designed with the following characteristics: (1) physical separation of two yeast populations, (2) homogeneity of the culture medium in both compartments, (3) fermentation kinetics monitored by weight loss due to CO2 release, and (4) independent monitoring of growth kinetics in the two compartments. This tool was used to compare mixed inoculations of S . cerevisiae / T. delbrueckii with and without physical separation. Our results revealed that physical contact/ proximity between S. cerevisiae and T. delbrueckii induced rapid death of T. delbrueckii, a phenomenon previously described and attributed to a cell-cell contact mechanism. In contrast, when physically separated from S. cerevisiae, T. delbrueckii maintained its viability and its metabolic activity had a marked impact on S. cerevisiae growth and viability. The double fermentor is thus a powerful tool for studying yeast interactions. Our findings shed new light on interaction mechanisms described in microorganism populations. © Springer-Verlag 2013.

Dimopoulou M.,CNRS Oenologie Research Unit | Hazo L.,CNRS Oenologie Research Unit | Dols-Lafargue M.,CNRS Oenologie Research Unit
International Journal of Food Microbiology | Year: 2012

Many food-grade bacteria produce exopolysaccharides (EPS) that may modify the food texture or affect their survival rate during food processing. This is the case of O. oeni, a bacterial species who drives malolactic fermentation in wine. The five strains analyzed in the present study all display both isolated genes dedicated to homopolysaccharide synthesis and gene clusters potentially associated with heteropolysaccharide synthesis. The number of isolated glycosyltransferase gene present and the gene composition of one of the operons change from one strain to the other. The soluble EPS yields and the EPS monomer composition vary depending on the strain and or the medium composition. O. oeni appears as a bacterium able to synthesize both homo and heteropolysaccharides. This unique property has rarely been described. Moreover, the abundance of the genetic determinants associated with EPS metabolism suggests that it is very important for the adaptation of the bacteria to wine. © 2011 Elsevier B.V.

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