Molecular and technological typing of autochthonous yeasts belonging to Hanseniaspora uvarum species

The wine is the product of the spontaneous grape must fermentation, induced by the indigenous micro flora, which catalyse the rapid, complete and efficient conversion of grape sugar into ethanol, carbon dioxide and other minor, but important metabolites by the complex biochemical process denoted as "alcoholic fermentation". The first step of the fermentation is characterized by the growth of yeast belonging to Kloeckera, Hanseniaspora, Candida, Metschnikowia e Pichia genera. These yeasts produce very low amount of alcohol but, they generate during the fermentation a large number of other secondary metabolites, which could positively influence the final bouquet of the wine. When the alcohol concentration raise to 4%, the second step of the fermentation process begins, which is mainly dominated by Saccharomyces cerevisiae. This yeast, commonly denoted as the "wine yeast", completes the fermentation, with high alcohol quantity but low production of secondary metabolites. The present study was aimed to the molecular and technological characterization of autochthonous yeast strains belonging to the Hanseniaspora uvarum species, isolated from spontaneous fermentation of Negroamaro and Primitivo grapes. The criterion for H. uvarum strain differentiation was provided by the PCR analysis of Random Amplified Polymorphic DNA (RAPD) markers and this assay which already demonstrated to allow the differentiation of yeast strains. The identified strains have been employed to fermentation laboratory tests after their inoculation in grape must and their oenological and technological properties have been evaluated. The fermented musts were further analyzed by high pressure liquid chromatography (HPLC) and gas-chromatography assays. The results of these molecular and technological analyses for the characterization of autochthonous H. uvarum strains will be discussed.