RODRIGUEZ maria eugenia
congresos y reuniones científicas
Congreso; 29th International Specialised Symposium on Yeast; 2011
There is a lot of information about yeast diversity in commercial fermentations (wine, cider); however, studies on traditional fermentations are scarce. No studies on traditional fermentations of pre-Columbian populations in Patagonia were reported. Some of the most relevant products include beverages obtained from seeds (i.e. Mudai, obtained from Araucaria araucana) or fruits (i.e. Chicha, made from apples) of autochthonous or introduced plants [1]. The aim of this work was to evaluate the yeast diversity of two traditional fermentations from Patagonia. Fermentative features of isolated yeasts were also analyzed. Methods. Yeasts were isolated from different stages of alcoholic fermentations carried out at laboratory scale mimicking traditional processes (Mudai and apple Chicha). Samples from Araucaria araucana trees were samples following prodecure described by Lopes et al. [2]. Yeast identification was carried out by molecular (ITS-RFLP and D1/D2 26S sequences). Saccharomyces isolates were additionally characterized by mtDNA-RFLP and ITS-RFLP of 33 nuclear genes [3]. New allele variants detected by PCR-RFLP were sequenced and compared with published data. Enological evaluation was carried out in micro-fermentations at 13°C on synthetic must. Wines obtained were evaluated in their physical-chemical characteristics. Results and discussion. Yeasts from apple chichas. At the begining of fermentation, the proportion of non-Saccharomyces yeasts varied between 25% and 84%, belonging to Hanseniaspora uvarum and Metschnikowia pulcherrima species. Saccharomyces genus completely dominated middle and end stages. S. uvarum was the most frequent species end stages of three fermentations (92% in average), while S. cerevisiae dominated the final stages of two fermentations (80% in average). Eight different mtDNA-RFLP patterns were detected among S. uvarum isolates and 6 among S. cerevisiae ones. One of the most frequently detected isolates of S. cerevisiae corresponded to a brewer yeast. Sequence analysis of nuclear genes obtained from S. cerevisiae isolates evidenced that most alleles were common to wine alleles present in Patagonian wine strains previously studied. Yeasts from Mudai and associated substrates. Yeast diversity in Mudai fermentation was very poor. Only Hanseniaspora uvarum and Saccharomyces cerevisiae were detected. All S. cerevisiae isolates showed a same mtDNA-RFLP pattern corresponding to the same brewery commercial pattern from chichas. With the aim to find wild Saccharomyces strains associated with Mudai fermentations, samples from Araucaria araucana seeds and barks from three regions in Andean Northpatagonia were analyzed. After isolation, identification and characterization, a total of 19 mtDNA-RFLP Saccharomyces patterns were found. PCR-RFLP pattens obtained for 33 nuclear genes distributed along Saccharomyces chromosomes, allowed us to identify these isolates as belonging to S. bayanus and S. uvarum species. Enological characterization. Yeast isolates representative of each S. bayanus and S. uvarum mtDNA-RFLP pattern detected were evaluated in their enologically relevant features in fermentations at 13°C. In general, regional isolates produced a higher concentration of glycerol and a lower concentration of ethanol than S. cerevisiae and they consumed the total quantity of glucose and fructose present in the medium. Conclusions. S. bayanus and S. uvarum isolates from traditional fermentations and related substrates from Patagonia were detected for the first time. They possess interesting enological features to be consider for wine fermentations at low temperature.