Search results for "bacteri"
showing 10 items of 5466 documents
Typical metabolic traits of two Oenococcus oeni strains isolated from Valpolicella wines
2004
Aims: Physiological comparison of two indigenous Oenococcus oeni strains, U1 and F3 isolated in the same area (Valpolicella, Italy) in order to select a performant starter for MLF in wine. Methods and Results: Growth rate, sugar and malate metabolism in FT80 media at pH 5·3 and 3·5 were analysed. The amount of total protein synthesized and the level of expression of the small Hsp Lo18 were evaluated by radiolabelling and immunodetection experiments after heat (42°C), acid (pH 3·5) and ethanol (12% v/v) stresses. Strain U1 showed significantly lower specific growth rate and growth yield in acid conditions than strain F3. However, strain U1 had a higher malate consumption capacity at pH 3·5…
Molecular Identification and Characterization of Wine Yeasts
2011
The transformation of grape must into wine is a complex microbiological process involving the sequential growth of bacteria and yeasts, although only the yeasts are responsible for alcoholic fermentation. In the past, winemaking was purely empirical, but it is now a well-understood, controlled process that has been gradually improved over time. Advances have largely been made possible by the development of molecular techniques to identify and characterize wine yeasts based on analysis of their DNA. These methods are rapid, reproducible, and sensitive, and continue to be used for a variety of purposes, such as analyzing variation in naturally occurring and inoculated yeast populations, monit…
The effects of freezing and freeze-drying ofOenococcus oeniupon induction of malolactic fermentation in red wine
2000
Summary The use of Oenococcus oeni starter cultures for the induction of malolactic fermentation (MLF) in wine permits control over the timing of the process and the quality of the wine. Successful inoculation of bacterial starter cultures into wine depends on the selection of suitable strains and on the preparation and conservation of those cultures. Medium for Leuconostoc oenos (MLO) is the best medium for easy and rapid growth of O. oeni cultures under laboratory controlled conditions for isolation and identification. However, this study showed that O. oeni cells inoculated in MLO failed to induce MLF in wine while cells grown in Medium of Preculture (MP) or wine, stored at −20 °C or fre…
Influence of epigallocatechin gallate and phenolic compounds from green tea on the growth of Oenococcus oeni
2007
Aims: To investigate the effect of phenolic compounds on the growth of Oenococcus oeni. Methods and Results: Oenococci are usually grown in media often supplemented with complex additives such as tomato juice. In order to improve our knowledge about the growth requirements of oenococci, we added several juices and leaf extracts such as green tea to the culture media and screened them for growth-stimulating substances to substitute complex supplements such as juices by more defined components. We found that also green tea could cause a growth stimulation of Oenococcus oeni strain B2. Conclusions: Further experiments showed that the stimulating effect was as a result of the phenolic compou…
Stress Responses of Oenococcus oeni
2011
Oenococcus oeni is an alcohol-tolerant, acidophilic lactic acid bacterium responsible for malolactic fermention in wine. The stress responses of O. oeni have been studied at both the molecular and physiological levels. Genes encoding stress proteins mainly belong to the CtsR regulon. Other regulation mechanisms seem to coexist in O. oeni and may correspond to posttranscriptional regulation. Maintenance of the cell membrane integrity under stress conditions seems to be a prerequisite for survival in wine. The active cell response to protect membrane function under stress conditions requires changes in fatty acid composition and involves stress proteins. Various solute transporters and energy…
Activation of wooden vats with selected lactic acid bacteria for the year-round production of traditional Vastedda-like cheese
2014
Vastedda is a pasta filata cheese made from raw ewes’ milk without the addition of starter cultures. Cheese production is carried out in wooden vats characterized by microbial biofilms hosting lactic acid bacteria (LAB) responsible for the acidification of the curds. Vastedda cheese was traditionally produced during the summer season, but it is currently produced throughout the year. In order to minimize production variability, several LAB were isolated from Vastedda PDO cheeses, characterized for their technological potential (Gaglio et al., 2014a) and selected to obtain the best strain combination for the production (Gaglio et al., 2014b). In this study, the multiple strain culture compos…
Electrical conductivity as a state indicator for the start-up period of anaerobic fixed-bed reactors.
2016
The aim of this work was to analyse the applicability of electrical conductivity sensors for on-line monitoring the start-up period of an anaerobic fixed-bed reactor. The evolution of bicarbonate concentration and methane production rate was analysed. Strong linear relationships between electrical conductivity and both bicarbonate concentration and methane production rate were observed. On-line estimations of the studied parameters were carried out in a new start-up period by applying simple linear regression models, which resulted in a good concordance between both observed and predicted values. Electrical conductivity sensors were therefore identified as an interesting method for monitori…
Near-infrared light-responsive and antibacterial injectable hydrogels with antioxidant activity based on a Dopamine-functionalized Gellan Gum for wou…
2022
The development of wound dressings with combined antioxidant, antibacterial and tissue adhesion functions has been a difficult medical task for the treatment of wound infections. We synthetized a dopamine and PEG functionalized Gellan Gum (GG) to produce an injectable hydrogel with radical scavenging activity having both specific and aspecific antibiotic/antimicrobial properties. Using starting GG with different molecular weights, we obtained two derivatives that have been used to prepare the gel precursor dispersion, that undergoes gelation in the presence of colistin and dried microparticles (MPs) functionalized on the surface with polydopamine (pDA). Both were used to dope the hydrogel, …
Mechanism of Antibacterial Activity via Morphology Change of α-AgVO3: Theoretical and Experimental Insights
2017
The electronic configuration, morphology, optical features, and antibacterial activity of metastable α-AgVO3 crystals have been discussed by a conciliation and association of the results acquired by experimental procedures and first-principles calculations. The α-AgVO3 powders were synthesized using a coprecipitation method at 10, 20, and 30 °C. By using a Wulff construction for all relevant low-index surfaces [(100), (010), (001), (110), (011), (101), and (111)], the fine-tuning of the desired morphologies can be achieved by controlling the values of the surface energies, thereby lending a microscopic understanding to the experimental results. The as-synthesized α-AgVO3 crystals display a …
Development and characterization of essential oil component-based polymer films: a potential approach to reduce bacterial biofilm
2013
The development of new polymeric materials aimed to control the bacterial biofilm appears to be an important practical approach. The goal of the present study was to prepare and characterize poly(ethylene-co-vinyl acetate) copolymer (EVA) films containing citronellol, eugenol, and linalool and evaluate their efficiency on growth and biofilm formation of Listeria monocytogenes, Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, and Pseudomonas aeruginosa in monospecies and dual species. The results showed that the addition of oil components influenced the elastic modulus (15 % decrease), the tensile stress (30 % decrease), the elongation at break (10 % increase), and the co…