Incidence des conditions de conservation des vins blancs sur leur teneur en composés soufrés volatils

Dans ce travail, nous avons étudié lincidence de quelques paramètres de conservation des vins issus des cépages blancs grecs, Batiki et Rhoditis, sur leur teneur en composés soufrés volatils. Il est demontré que le stade du sulfitage des vins nouveaux joue un rôle important sur la formation de ces substances, ainsi que laération qui entraîne leur diminution. De plus, la conservation des vins en barrique ou en cuve, avec les lies ou non, influence dune manière différente la teneur des vins en substances soufrées volatiles. Influence of white wine conservation conditions on the levels of volatile sulphur compoundsIn the present study, the effects of various parameters of white wine conservation on the level of volatile sulphur compounds were examined. Wines from the Greek white cvs Batiki and Rhoditis were fermented. H2S was analysed colorimetrically, the more volatile sulphur compounds by headspace-gas chromatography (GC) coupled with flame photometry detection (FPD) and the less volatile sulphur compounds by liquid extraction-GC/MS. The best time to sulphurize a young wine is 5-6 d after the end of alcoholic fermentation in order to avoid the accumulation of sulphur substances, especially in wines intended to age on lees, Aeration of wine causes a notable decrease of the more volatile sulphur compounds, whereas the diminution is less important for the less volatile sulphur compounds. Furthermore, the amount of volatile sulphur compounds is affected by the conservation of wines in barriques or in stainless tanks, the duration of contact of wine with its lees, as well as the duration of conservation

Molecular identification of wine yeasts at species or strain level: A case study with strains from two vine-growing areas of Greece

The composition of wine yeast populations, present during spontaneous fermentation of musts from two wine-producing areas of Greece (Amyndeon and Santorini) and followed for two consecutive years, were studied using a range of molecular techniques. Internal Transcribed Spacer (ITS) ribotyping was convincingly applied for yeast species identification, proving its usefulness as a reliable tool for the rapid characterization of species composition in yeast population studies. Restriction Fragment Length Polymorphism (RFLP) of mitochondrial DNA (mtDNA) was shown to be a convenient criterion for the detection of intraspecies genetic diversity of both Saccharomyces and non-Saccharomyces isolate populations. Similarly, polymorphism of amplified δ interspersed element sequences provided an additional criterion for S. cerevisiae strain differentiation. Comparative analysis of S. cerevisiae genetic diversity, using mtDNA restriction patterns and δ-amplification profiles, showed a similar discriminative power of the two techniques. However, by combining these approaches it was possible to distinguish/characterize strains of the same species and draw useful conclusions about yeast diversity during alcoholic fermentation. The most significant findings in population dynamics of yeasts in the spontaneous fermentations were (i) almost complete absence of non-S.cerevisiae species from fermentations of must originating from the island Santorini, (ii) a well recorded strain polymorphism in populations of non-Saccharomyces species originating from Amyndeon and (iii) an unexpected polymorphism concerning S. cerevisiae populations, much greater than ever reported before in similar studies with wine yeasts of other geographical regions

Molecular identification of wine yeasts at species or strain level: A case study with strains from two vine-growing areas of Greece

The composition of wine yeast populations, present during spontaneous fermentation of musts from two wine-producing areas of Greece (Amyndeon and Santorini) and followed for two consecutive years, were studied using a range of molecular techniques. Internal Transcribed Spacer (ITS) ribotyping was convincingly applied for yeast species identification, proving its usefulness as a reliable tool for the rapid characterization of species composition in yeast population studies. Restriction Fragment Length Polymorphism (RFLP) of mitochondrial DNA (mtDNA) was shown to be a convenient criterion for the detection of intraspecies genetic diversity of both Saccharomyces and non-Saccharomyces isolate populations. Similarly, polymorphism of amplified δ interspersed element sequences provided an additional criterion for S. cerevisiae strain differentiation. Comparative analysis of S. cerevisiae genetic diversity, using mtDNA restriction patterns and δ-amplification profiles, showed a similar discriminative power of the two techniques. However, by combining these approaches it was possible to distinguish/characterize strains of the same species and draw useful conclusions about yeast diversity during alcoholic fermentation. The most significant findings in population dynamics of yeasts in the spontaneous fermentations were (i) almost complete absence of non-S.cerevisiae species from fermentations of must originating from the island Santorini, (ii) a well recorded strain polymorphism in populations of non-Saccharomyces species originating from Amyndeon and (iii) an unexpected polymorphism concerning S. cerevisiae populations, much greater than ever reported before in similar studies with wine yeasts of other geographical regions

The mitochondrial genome of the wine yeast Hanseniaspora uvarum: A unique genome organization among yeast/fungal counterparts

The complete sequence of the apiculate wine yeast Hanseniaspora uvarum mtDNA has been determined and analysed. It is an extremely compact linear molecule containing the shortest functional region ever found in fungi (11 094 bp long), flanked by Type 2 telomeric inverted repeats. The latter contained a 2704-bp-long subterminal region and tandem repeats of 839-bp units. In consequence, a population of mtDNA molecules that differed at the number of their telomeric reiterations was detected. The functional region of the mitochondrial genome coded for 32 genes, which included seven subunits of respiratory complexes and ATP synthase (the genes encoding for NADH oxidoreductase subunits were absent), two rRNAs and 23 tRNA genes which recognized codons for all amino acids. A single intron interrupted the cytochrome oxidase subunit 1 gene. A number of reasons contributed towards its strikingly small size, namely: (1) the remarkable size reduction (by >40%) of the rns and rnl genes; (2) that most tRNA genes and five of the seven protein-coding genes were the shortest among known yeast homologs; and (3) that the noncoding regions were restricted to 5.1% of the genome. In addition, the genome showed multiple changes in the orientation of transcription and the gene order differed drastically from other yeasts. When all protein coding gene sequences were considered as one unit and were compared with the corresponding molecules from all other complete mtDNAs of yeasts, the phylogenetic trees constructed robustly supported its placement basal to the yeast species of the 'Saccharomyces complex', demonstrating the advantage of this approach over single-gene or multigene approaches of unlinked genes. © 2005 Federation of European Microbiological Societies Published by Blackwell Publishing Ltd. All rights reserved

Complete mitochondrial genome sequence of the wine yeast Candida zemplinina: Intraspecies distribution of a novel group-IIB1 intron with eubacterial affiliations

The mtDNA of the ascomycetous wine yeast Candida zemplinina is a circularly mapping genome of 23 114 bp. It contains 35 genes coding for the seven basic subunits of oxidative phosporylation found in yeasts (the genes encoding for NADH oxidoreductase subunits are absent), the ribosomal protein Var1, two rRNAs and 25 tRNA genes. Although protein phylogenetic analysis showed a divergent mitochondrial genome, several traits appeared preserved. The conserved gene blocks between the mtDNAs of C. zemplinina and Candida glabrata were maintained and changes in gene order and putative promoters were due to restricted genome reshuffling. New heterogeneous hairpin elements were identified scattered throughout cox1 introns. The large subunit rRNA gene harboured the first group-IIB1 intron containing a putative active reverse transcriptase (RT) in mitochondrial genomes of fungi. Phylogenetic analysis of the RT protein confirmed its closer relationship to eubacterial intronic RTs, while being only distantly related to all other fungal mitochondrial group-II introns and RTs. The findings point towards an early migration event of a eubacterial group-II intron to the mitochondrial genome of C. zemplinina. © 2007 Federation of European Microbiological Societies