Yeast biota associated with traditional fermented beverages in Patagonia

CHRISTIAN A. LOPES; JULIETA S. SAEZ; MARCELA P. SANGORRÍN; ADRIANA C. CABALLERO

Carlos Paz, Córdoba, Argentina.

Congreso; VI Congreso Argentino de Microbiología General; 2009

Sociedad Argentina de Microbiología General (SAMIGE)

Several raw sources, including cereals and fruits involved wild fruits such as strawberries (Fragaria chiloensis), ?maqui? (Aristotelia chilensis), ?calafate? (Berberis spp.), apples (Malus sp.), as well as seeds of different plants have been traditionally used by aboriginal communities in Patagonia to prepare different fermented beverages. A particularly interesting fermented beverage is that obtained from seeds of the Pehuen tree (Araucaria araucana), from which the Mapuche´s communities prepare the fermented beverage called Mudai. No works involving the microbial biota present in Mudai and other traditional fermented beverages in Patagonia have been published until now.With the aim to investigate this particular yeast biota for the first time, juices obtained from Pehuen seeds and wild apples were obtained in the traditional way and fermented in sterile flasks under laboratory conditions (3 fermentations from Pehuen seeds and 2 from apple). Yeast sampling in complete medium was carried out during the processes, showing maximum population densities of 1.5x108cfu mL-1. Molecular identification of these colonies by using ITS1-5.8S-ITS2 PCR-RFLP and sequence analyses, revealed the presence of only two yeast species at the beginning of Mudai fermentation: Hanseniaspora uvarum and Saccharomyces cerevisiae in percentages of 80% and 20% of the total biomass respectively. In Apple fermentations, non-Saccharomyces yeasts corresponded to 25% and 84% of the total isolates at the begining of the two analyzed fermentations respectively, including isolates belonging to H. uvarum and Metschnikowia pulcherrima. In subsequent stages of all Mudai and apple fermentations, the yeast biota corresponded exclusively to S. cerevisiae in all analyzed fermentations.Intraspecific analysis of the S. cerevisiae isolates from Mudai fermentations by means of mtDNA-RFLP analysis evidenced a single restriction pattern. This kind of biological homogeneity is frequently observed in inoculated fermentations in which the yeast starter selected culture dominate the fermentation process, but it is not expected to occur in natural processes. Traditional production of this beverage does not involve the use of commercial yeasts; however, the environment in which this product is elaborated is in permanent contact with the commercial yeasts used in bread making. MtDNA-RFLP analysis of commercial bakery yeasts showed the same molecular pattern detected in Mudai fermentations, evidencing a cross-contamination of yeasts in these traditional fermented products. The intraspecific diversity in S. cerevisiae populations from apple fermentation samples are being currently analyzed in order to find indigenous Saccharomyces isolates and to evaluate its phylogenetic relationships with regards to wine strains of this species.