The quality of fermented foods and beverages is partially determined by the microorganisms used for their production. For instance, the secondary character of wine is determined by sensory characteristics that arise from the direct action of microorganisms on the substrate. The fermentation of grape must into wine is an ecologically complex process, in which bacteria and other microorganisms, especially yeasts, play a crucial role. The strains of Saccharomyces cerevisiae involved in fermentation play an important part in the characteristics of the final product and the diversity of S. cerevisiae strains present in spontaneous fermentation contribute to the chemical composition and sensory qualities of the resulting wine. 1
Therefore, one of the most important technological advances in wine-making was the inoculation of grape juice with selected cultures of S. cerevisiae. 2 This approach is based on the evidence that microbiological control of the fermentation process allows better management of this alcoholic fermentation. It is known that selected strains of S. cerevisiae suppress indigenous non-Saccharomyces species and dominate the fermentation process. 3, 4 and 5
Nowadays, novel biotechnological approaches in winemaking are used in several aspects of the fermentation industry. Apart from the monitoring of the microbial populations and the control of the spoilage yeasts, attention is focused also on the selection and utilization of the starter cultures coming from one's own vineyard, which can enhance the regional character of the wine.6 and 7 The metabolic peculiarities and the physiological properties of S. cerevisiae yeast may lead to the formation of metabolites and the transformation of grape substances that may enrich the wine flavor. 7 Certain criteria need to be met in order to guarantee the desirable features of the yeast strains selected. The most important ones are: tolerance to ethanol; growth at high sugar concentrations; resistance to sulfur dioxide; low production of hydrogen sulfide; production of killer toxins or some enzymatic activities.8
Furthermore, only reliable and rapid identification of the yeast species during the process and the quality control enables enologists to assess the role of yeasts as a main protagonist of alcoholic fermentation or as a contaminant. The utilization of molecular methods enabled rapid and precise identification of the yeasts at the species or strain level.1 Mercado et al.9 reported that Saccharomyces populations are represented by multiple strains, even in inoculated fermentations. Therefore, it is important to have simple and appropriate methods that allow discrimination at the strain level.
This study is focused on indigenous S. cerevisiae strain (i) selection, (ii) identification and (iii) technological characterization. Yeasts were isolated from grapes and musts during the production of wines. We selected two types of wine varieties – Sauvignon blanc and Pinot noir coming from an organic and integrated treated vineyard situated in South Moravia, Czech Republic. Our objective was also focused on the selection of the identification approaches that will be simple and suitable for rapid and reliable strain identification. Therefore, isolates of S. cerevisiae were identified and grouped by several molecular approaches such as ITS-PCR-RFLP, PCR-fingerprinting, species-specific primers and interdelta PCR typing. The combination of these techniques enabled rapid detection, identification and typing of different S. cerevisiae strains. Finally, the isolated strains were screened for selected technological properties important in the winemaking process and for further application as the starter cultures. To sum up, this study has demonstrated the importance of selection of an appropriate and rapid identification technique and also determination of some important oenological properties.