1,720,993 research outputs found
Focus on biodiversity of technological yeasts in vineyard: territory influence, role of grape variety and importance of sampling site on grapevine
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Aspetti microbiologici del trattamento di acidificazione della vinaccia ed effetti sulla componente aromatica
No full textThis work was aimed at focusing the effects of an acidification treatment of grape pomace destined to the production of Grappa, on microbial population and on aromatic compounds after distillation. Grape marcs were acidified up to pH 2,9 at the beginning of the storage period. In order to evaluate the dynamics of the indigenous microorganisms, three different samplings were made, at T0, after 15 days (T15) and after 43 days (T43). Quantification of yeasts and bacteria, evidenced that lowering of the pH limits bacterial growth throughout the ensilage period. Genetic analyses of yeast isolates showed that the species succession lead to non-Saccharomyces species dominance in both conditions although acidified marc showed a lower percentage of Saccharomyces at any sampling time. Gas chromatographic analysis showed a remarkable change in the aromatic profile of distilled grape marcs at the end of the storage, thus evidencing the reduction of the main volatile products associated with potential off-flavours
Increasing vineyard biodiversity by indigenous Saccharomyces cerevisiae strains spreading: yeast persistence and effect on spontaneous grape must fermentations
No full textBackground:
Recent studies indicate that S. cerevisiae strain biodiversity in vineyard is highly variable and seems to be influenced not only by grapevine varieties but also by pesticide treatments. High biodiversity level is necessary to guarantee spontaneous fermentation that recently have been re-evaluated both for positively influencing sensorial characteristics of wine and for supporting a more “natural” management of wine-making process.
Objectives:
The aim of this work was to increase yeast biodiversity by spraying five indigenous S. cerevisiae strains on grape vineyards and to evaluate their persistence and colonizing ability.
Methods:
From a collection of vineyard yeasts isolated in the area of “Prosecco di Conegliano-Valdobbiadene” DOCG five strains were chosen and sprayed on two vineyard of the same wine-making region: one was cultivated using conventional practices and the other grown under organic farming methods. Bark and leaf samples were collected and added to synthetic must. After fermentation yeasts were isolated and mtDNA analysis was performed to identify the inoculated strains.
Conclusions:
The presence of the introduced strains was monitored 10 days and 2 months after yeast culture spray. Results on strain ability to colonize grapevine bark are also reported
Molecular and physiological characterization of Saccharomyces cerevisiae strains from fermented must and grape marcs
No full textSaccharomyces cerevisiae species dominate the middle-final phases of fermentation in must, but it is also responsible for
ethanol production during storage of grape marcs, the main by-product of wine industry, which can be processed for the
production of distillates. Grape marc is quite different than must in terms of composition as it consists of solid parts
remaining after juice separation, but also for chemical properties. Due to the higher pH, the presence of sugars and other
nutritional compounds, it seems to be a more favourable environment than must for the development of yeasts.
The aim of this work was to compare the biodiversity of S.cerevisiae strains during spontaneous fermentation of must and
grape marcs obtained from the same grape processing, and to study the physiological properties that can be responsible
for strain adaptation to the two enological environments. Two grape varieties from north-east of Italy were considered,
Glera and Tocai friulano. Mitochondrial DNA analysis performed on Saccharomyces isolated after 6 days and at the end
of fermentation, allowed the strain characterization of 100 isolates from must and grape marc, respectively. Some strains
were found to be in common to both environments, but others prevailed only on marc. The causes were investigated
analyzing some physiological characteristics that can confer an advantage to strains developing in grape marcs as growth
at different pH values and yeast enzymatic activities for plant component degradation. Since skins can be richer that must
of fungicide residues, resistance of yeasts to increasing copper concentration was also evaluated
Characterization of natural yeast population on dried friularo grapes for passito wine production
No full textAspects of Plant-Microbe Interactionsin Heavy Metal Polluted Soil
No full textThe role of soil microbiota, specifically rhizospheric microorganisms, in the development of phytoremediation techniques has to be elucidated in order to speed up the process and to optimize the rate of mobilization/absorption of pollutants. To meet such a purpose, several heavy metal resistant bacterial strains were isolated from a contaminated soil and from the rhizosphere of some spontaneous plants grown therein, such as Brassica sp., Trifolium repens, Trifolium pratense and Chenopodium album. Colonization of the rhizosphere is known to be helpful for bacteria, but their presence is also supposed to be functional to the plants, especially if in connection with their ability to produce Plant Growth Promoting (PGP) compounds (e.g. indole-acetic acid) or to protect the plant from pathogens. Therefore, in such an adverse environment, plants and bacteria surely take advantage by cooperating. Several bacterial isolates were tested and found to be capable of producing PGP compounds. Among them, a highly heavy metal resistant strain (Br-10) was isolated from the roots of a spontaneous plant belonging to the Brassicaceae family, whose members are known to accumulate heavy metals, and identified by phenotypic tests and 16S rDNA analysis as Serratia plymuthica. To evaluate its putative biocontrol activity, a screening of its antagonistic properties against various soil phytopathogens was also undertaken. Among the pathogenic fungi tested, a strain of Phytophtora megasperma f. sp. glycinea was found to be sensitive. Preliminary investigations of Br-10 resistance mechanisms, performed through hybridization studies on genomic DNA, suggested for S. plymuthica strain Br-10 the existence of a resistance mechanism different from that codified by the well-known czc gene cluster of Alcaligenes eutrophus that encodes for cadmium, zinc and cobalt resistance through an efflux system. By the use of Inductively Coupled Plasma analysis Cd was found to be preferentially adsorbed or accumulated rather than being forced out of the cell or not imported at all. Growth kinetics studies revealed that increasing Cd levels do not seem to affect cell growth up to the stationary phase, while having a clear impact on cell viability during the stationary phase
Effetti di alcuni trattamenti tecnologici (acidificazione e inoculo di lieviti) sulla microflora della vinaccia durante la fase di stoccaggio e implicazioni nella qualità del distillato
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