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131 Regodon, J. A., Perez, F., Valdes, M. E., De Miguel, C. & Ramirez, M. (1997): A simple and effective procedure for selection of wine yeast strains. F d Microbiol. , 14 , 247
Initiated by the Association “Wine Route of Etyek Wine District”, the objectives of this study were to isolate and identify autochthonous yeast strains from local wines and to determine their oenologically important properties. The first aim of this work was to characterize the taxonomic and phenotypic diversity of the representative Saccharomyces yeast strains that dominate the spontaneous fermentations in this wine district. The results obtained by molecular ribotyping (ARDRA) revealed a strong dominance of S. cerevisiae, but S. bayanus var. uvarum was also present sporadically. Some of the natural isolates exhibited high volatile acid production or poor fermentation capacity, which imply a quality risk in spontaneous fermentations. Most of the isolates, however, displayed good oenological features during lab scale fermentations. As the second aim of this work, the most promising, selected strains were further tested for oenological properties in microvinification scale and, finally, in large scale fermentations. The analytical and sensory analysis proved that selected strains, including S. bayanus var. uvarum, can be used as local starter cultures, which may contribute to the typicality of the local wines in comparison with commercial starters.
Solid phase microextraction (SPME) coupled to fast capillary gas chromatography was used for monitoring the wine fermentation process. This combination offers a simple, quick and sensitive approach suitable for characterization of head-space components of wines during the fermentation process without a complicated sample preparation procedure. In this work this method was used to observe the differences in aroma production between three different commercial yeasts and the indigenous yeast flora.
290 Jiranek, V. (1995) Amino acid and ammonium utilization by Saccharomyces cerevisiae wine yeasts from a chemically defined medium. Am. Enol. Viticult. 46 , 75
In this study a simple and effective method was developed for the isolation of Saccharomyces strains from grapes. Aseptically collected grape samples were processed by enrichment in a nutritive basal medium supplemented with 10% (v/v) methanol followed by isolation of yeast strains. Sixteen of the 18 grape samples yielded Saccharomyces strain(s). More than 70% of the isolates belonged to the genus Saccharomyces. Based on phenotype and electrophoretic karyotyping, all strains of Saccharomyces were identified as S. cerevisiae. For several grape samples, varying physiological characters, the number of spores per asci, and the observed chromosome length polymorphisms provided evidence for diversity of S. cerevisiae strains obtained by this enrichment in methanol-containing broth. Results indicated that enrichment in methanol-containing broth is an effective alternative method to facilitate isolation of Saccharomyces strains from grapes. The enrichment method described in this work provides a simple and effective tool for isolation of Saccharomyces strains from grapes. The method may be applied in studying wine fermentation ecology, as well as for the isolation of potential starter strains from grapes.
viticulture, dried wine yeast species S. cerevisiae and Saccharomyces bayanus are used in the Czech Republic ( Michlovský, 2014 ). Research on new suitable yeasts is still ongoing, with the aim of discovering yeast strains with unique properties
day. The must obtained after pressing was divided into aliquots of 100 mL, pasteurised (110 °C for 10 min), inoculated at 5% in triplicate with the wine yeasts, and incubated at 20 °C. The weight loss caused by CO 2 production after three days of
Wine fermentation is a complex microbiological process in which yeasts predominate. It is long debated whether yeasts occurring on the surface of grapes or the resident yeasts on the winery equipment play the primary role in conducting the fermentation. The origin, development, changes and succession of various yeast species can be followed using specific molecular techniques allowing the differentiation and typing of yeast strains. Techniques such as pulsed field gel electrophoresis of chromosomal DNA, restriction fragment length polymorphism analysis, and polymerase chain reaction (PCR)-based methods have recently been employed in studying the microbiology of wine making. These shed new light on the dynamics of fermentation started spontaneously or directed by the inoculation of starter cultures.
Roots of classical yeast genetics go back to the early work of Lindegreen in the 1930s, who studied thallism, sporulation and inheritance of wine yeast strains belonging to S. cerevisiae. Consequent mutation and hybridization of heterothallic S. cerevisae strains resulted in the discovery of life cycle and mating type system, as well as construction of the genetic map. Elaboration of induced mutation and controlled hybridization of yeast strains opened up new possibilities for the genetic analysis of technologically important properties and for the production of improved industrial strains, but a big drawback was the widely different genetic properties of laboratory and industrial yeast strains. Genetic analysis and mapping of industrial strains were generally hindered because of homothallism, poor sporulation and/or low spore viability of brewing and wine yeast strains [1, 2]. In spite of this, there are a few examples of the application of sexual hybridization in the study of genetic control of important technological properties, e.g. sugar utilization, flocculation and flavor production in brewing yeast strains [3] or in the improvement of ethanol producing S. cerevisiae strains [4]. Rare mating and application of karyogamy deficient (kar−) mutants also proved useful in strain improvement [5].Importance of yeasts in biotechnology is enormous. This includes food and beverage fermentation processes where a wide range of yeast species are playing role, but S. cerevisiae is undoubtedly the most important species among them. New biotechnology is aiming to improve these technologies, but besides this, a completely new area of yeast utilization has been emerged, especially in the pharmaceutical and medical areas. Without decreasing the importance of S. cerevisiae, numerous other yeast species, e.g. Kluyveromyces lactis, Hansenula polymorpha, Pichia pastoris, Schizosaccharomyces pombe and Yarrowia lipolytica have gained increasing potentialities in the modern fermentation biotechnology [6].Developments in yeast genetics, biochemistry, physiology and process engineering provided bases of rapid development in modern biotechnology, but elaboration of the recombinant DNA technique is far the most important milestone in this field. Other molecular genetic techniques, as molecular genotyping of yeast strains proved also very beneficial in yeast fermentation technologies, because dynamics of both the natural and inoculated yeast biota could be followed by these versatile DNA-based techniques.
Summary
The major objective of the present work was to compare the kinetic study of alcoholic fermentations conducted in the presence of wheat supported biocatalysts in laboratory scale and in a scale-up system of 80 L and to compare these results with those reported in literature. The kinetic study of fermentation processes was accomplished with the technique of reversed flow gas chromatography (RFGC), which is a version of inverse gas chromatography. The wine yeast species used was Saccharomyces cerevisiae AXAZ-1, and fermentations were conducted between 20 and 2°C. At low temperatures, maximal ethanol productivity and fermentation rate were reduced. The rate constants, determined through a mathematical model obtained from RFGC, were higher in the laboratory scale comparing to the scale-up system at the temperatures of 20 and 15°C. However, with the reduction of temperature, both systems presented almost similar values proving the great fermentative ability of immobilized cells even at extremely low temperatures. Activation energies of the alcoholic fermentations in the two systems presented their higher values at the second phase (stationary) compared to those observed at the other two phases (growth and decline).
