Vladimir Jiranek

Learn More
Saccharomyces cerevisiae wine-producing yeast cultures grown under model winemaking conditions could be induced to liberate hydrogen sulfide (H2S) by starvation for assimilable nitrogen. The amount of H2S produced was dependent on the yeast strain, the sulfur precursor compound, the culture growth rate, and the activity of the sulfite reductase enzyme (EC(More)
The characterisation of wine yeasts and the complex metabolic processes influencing wine fermentation and the quality of wine might best be achieved by exploiting the standard classical and recombinant genetic techniques which have been successfully used with laboratory strains. However, application of these techniques to industrial strains has been(More)
We report the cloning and characterization of EstB28, the first esterase to be so characterized from the wine-associated lactic acid bacterium, Oenococcus oeni. The published sequence for O. oeni strain PSU-1 was used to identify putative esterase genes and design PCR primers in order to amplify the corresponding region from strain Ooeni28, an isolate(More)
Dekkera and Brettanomyces yeast are important spoilage organisms in a number of food and beverage products. Isolates of both genera were cultured in a defined medium and supplemented with hydroxycinnamic acids and vinylphenols to investigate their influence on growth and the formation of ethyl phenol derivatives. The growth rate of Brettanomyces species in(More)
Simple phenolic components of wine, hydroxycinnamic acids (HCAs) are known to have antimicrobial properties. This study sought to determine the potential of ferulic acid as an antifungal agent for the control of Dekkera. Growth was inhibited by all HCAs examined in this study, with ferulic acid being the most potent at all concentrations. In the presence of(More)
AIM To clone and characterize two related intracellular esterases from Oenococcus oeni and Lactobacillus hilgardii under wine-like conditions. METHODS AND RESULTS The published genome sequences for O. oeni and Lact. hilgardii were used to identify, clone and purify putative esterase genes from these species designated EstCOo8 and EstC34, respectively.(More)
Esters are an important group of volatile compounds that can contribute to wine flavour. Wine lactic acid bacteria (LAB) have been shown to produce esterases capable of hydrolysing ester substrates. This study aims to characterise the esterase activities of nine LAB strains under important wine conditions, namely, acidic conditions, low temperature (to(More)
Volatile phenols are produced by Dekkera yeasts and are of organoleptic importance in alcoholic beverages. The key compound in this respect is 4-ethylphenol, responsible for the medicinal and phenolic aromas in spoiled wines. The microbial synthesis of volatile phenols is thought to occur in two steps, beginning with naturally occurring hydroxycinnamic(More)
Malolactic enzymes (MLE) are known to directly convert L-malic acid into L-lactic acid with a catalytical requirement of nicotinamide adenine dinucleotide (NAD (+) ) and Mn ( 2+) ; however, the reaction mechanism is still unclear. To study a MLE, the structural gene from Oenococcus oeni strain DSM 20255 was heterologously expressed in Escherichia coli,(More)
Wine fermentation is a harsh ecological niche to which wine yeast are well adapted. The initial high osmotic pressure and acidity of grape juice is followed by nutrient depletion and increasing concentrations of ethanol as the fermentation progresses. Yeast’s adaptation to these and many other environmental stresses, enables successful completion of(More)