Quantifying the Effects of Ethanol and Temperature on the Fitness Advantage of Predominant Strains Occurring in Spontaneous Wine Fermentations.

Different strains are simultaneously or in succession involved in spontaneous wine fermentations. In general, few strains occur at percentages higher than 50% of the total yeast isolates (predominant strains), while a variable number of other strains are present at percentages much lower (secondary strains). Since strains participating in alcoholic fermentations may differently affect the chemical and sensory qualities of resulting wines, it is of great importance to assess whether the predominant strains possess a "dominant character.

Effect of selected strains of lactobacilli on the antioxidant and anti-inflammatory properties of sourdough.

Sourdough fermentation of cereal foods is an excellent source of obtaining peptides due to the ability of lactic acid bacteria to activate cereal proteases and produce strain-specific peptidases. With the aim of identifying the lactic acid bacterial strains potentially most effective in producing bioactive peptides, 131 lactobacilli isolates from Italian sourdoughs, used in baking technology, have been screened for proteolytic and peptidase activity. Of these, 23 strains were selected and singly inoculated in liquid sourdoughs from which a Low Molecular Weight fraction containing peptides was obtained.

Diversity of Saccharomyces cerevisiae Strains Isolated from Two Italian Wine-Producing Regions.

Numerous studies, based on different molecular techniques analyzing DNA polymorphism, have provided evidence that indigenous Saccharomyces cerevisiae populations display biogeographic patterns. Since the differentiated populations of S. cerevisiae seem to be responsible for the regional identity of wine, the aim of this work was to assess a possible relationship between the diversity and the geographical origin of indigenous S.

Enumeration and rapid identification of yeasts during extraction processes of extra virgin olive oil in Tuscany.

The aim of this study was to evaluate the occurrence of yeast populations during different olive oil extraction processes, carried out in three consecutive years in Tuscany (Italy), by analysing crushed pastes, kneaded pastes, oil from decanter and pomaces. The results showed yeast concentrations ranging between 10(3) and 10(5) CFU/g or per mL. Seventeen dominant yeast species were identified by random amplified polymorphic DNA with primer M13 and their identification was confirmed by restriction fragments length polymorphism of ribosomal internal transcribed spacer and sequencing rRNA genes.

Typing of Lactobacillus sanfranciscensis isolates from traditional sourdoughs by combining conventional and multiplex RAPD-PCR profiles.

In the present work, a rapid and reproducible molecular method, based on the combination of conventional and multiplex RAPD-PCR reactions, was developed for typing Lactobacillus sanfranciscensis isolates from traditional sourdoughs. At first, four random primers, two used singly and two combined with the primer RD1, were chosen on the basis of their differentiating capability and reproducibility. The four resulting profiles for each isolate were integrated into a unique profile to be statistically treated by cluster analysis.

Stable and non-competitive association of Saccharomyces cerevisiae, Candida milleri and Lactobacillus sanfranciscensis during manufacture of two traditional sourdough baked goods.

The microbiota occurring in all the manufacturing phases of two Italian sourdough sweet-leavened baked goods (a typical Genoese dry biscuit, Lagaccio, and a soft stuffed North Italian typical cake, Panettone) were investigated over a period of three years. The two sourdough mother sponges were characterized by the stable presence of three dominant microbial species in potential competition for carbohydrates: Lactobacillus sanfranciscensis, Candida milleri, and Saccharomyces cerevisiae. Genotypic and phenotypic characterizations of microbial isolates pointed out that each mother sponge harbored its own strains, well distinguishable by molecular methods of analysis but not differing in their main metabolic properties from those known for the corresponding species.

Populations of exopolysaccharide-producing cyanobacteria and diatoms in the mucilaginous benthic aggregates of the Tyrrhenian Sea (Tuscan Archipelago).

The microalgal community of benthic mucilages sampled in various sites of the Tuscan Archipelago during the period May 1999-July 2002, was always dominated by diatoms. Synedra, Licmophora and Navicula were the most frequently found genera, their presence having been observed within all the period under study; other ten genera of diatoms were found in the benthic mucilages, but their presence was dependent on the month and the year of observation. As concerns the cyanobacterial community, the filamentous genera Leptolyngbya, Lyngbya and Rivularia were the most frequently found, independently on the period and the year of samplings, while other genera, namely Oscillatoria, Symploca, Aphanocapsa and Gloeocapsa, were less frequently observed.

Putrescine accumulation in wine: role of Oenococcus oeni.

Putrescine, the most abundant biogenic amine in wine, was proved to be produced by Oenococcus oeni strains in wine not only from ornithine but also from arginine. In this case, putrescine may originate from strains possessing the complete enzyme system to convert arginine to putrescine or by a metabiotic association, with an exchange of ornithine, between strains capable of metabolizing arginine to ornithine but unable to produce putrescine and strains capable of producing putrescine from ornithine but unable to degrade arginine. Putrescine production by this metabiotic association occurred once the malolactic fermentation was completed, whereas conversion of ornithine to putrescine by a single culture of the ornithine decarboxylating strain concurred with the degradation of malic acid.

Oenological properties of Hanseniaspora osmophila and Kloeckera corticis from wines produced by spontaneous fermentations of normal and dried grapes.

Strains of Hanseniaspora osmophila and Kloeckera corticis, isolated from wines produced by spontaneous fermentations of normal and dried grapes, were characterized for their fermentation behavior with and without SO(2) at 25 degrees C. All isolates behaved as glucophilic yeasts and yielded ethanol at concentrations of about 9% (v/v); acetic acid, acetaldehyde, ethyl acetate and acetoin were always produced to high concentrations. SO(2) addition had no significant effect on growth yield and fermentation rate.

Extracellular polysaccharide synthesis by Nostoc strains as affected by N source and light intensity.

A study on the effect of two of the main factors affecting energy flux in N(2)-fixing cyanobacteria, i.e. light intensity and availability of combined nitrogen, on the synthesis of soluble exopolysaccharides was carried out with three strains of the genus Nostoc (PCC 7413, PCC 7936, and PCC 8113) presenting different capsular polysaccharidic morphologies and released polysaccharide productions.

Phenotypic and genotypic characterization of Oenococcus oeni strains isolated from Italian wines.

A phenotypic and genotypic characterization of 84 Oenococcus oeni isolates from Italian wines of different oenological areas was carried out. Numerical analysis of fatty acid profiles grouped the isolates into two clusters at low level of similarity (63%), the minor cluster containing seven isolates besides the type and the reference strains. Forthy-eight O.

Biogenic amine production by Oenococcus oeni.

The biogenic amine-producing capability of several Oenococcus oeni strains, originally isolated from different Italian wines, was determined. The amine-producing capability was quali-quantitatively variable among the strains: out of the 44 strains investigated under optimal growth conditions, more than 60% were able to produce histamine, at concentrations ranging from 1.0 to 33 mg/L, and about 16% showed the additional capability to form both putrescine and cadaverine, to different extents and variable relative proportions.

Effect of oleic acid on Oenococcus oeni strains and Malolactic fermentation in wine.

A different capability to assimilate oleic acid from the culture medium has been demonstrated among malolactic Oenococcus oeni strains. Strains possessing higher percentages of oleic acid and its methylated derivative, dihydrosterculic acid, in their fatty acid profile showed higher cell viability and carried out a complete malolactic fermentation after their transfer into a wine lacking oleic acid. Wine supplementation with Tween 80 (polyoxyethylene-sorbitan-mono-oleate) enhanced cell survival of strains with lower capability to assimilate oleic acid and caused cell growth of strains with higher assimilative capacity, suggesting that oleic acid may act in wine as a survival factor for the former strains and as a growth factor for the latter strains.