Few studies have been performed on the characterization of yeasts involved in the production of agave distilled beverages and their individual fermentation properties. In this study, a comparison and evaluation of yeasts of different origins in the tequila and wine industries were carried out for technological traits. Fermentations were carried out in high (300 g l(-1)) and low (30 g l(-1)) sugar concentrations of Agave tequilana juice, in musts obtained from Fiano (white) and Aglianico (red) grapes and in YPD medium (with 270 g l(-1) of glucose added) as a control. Grape yeasts exhibited a reduced performance in high-sugar agave fermentation, while both agave and grape yeasts showed similar fermentation behaviour in grape musts. Production levels of volatile compounds by grape and agave yeasts differed in both fermentations.

Aims:The characterization by molecular and physiological methods of wild apiculate strains, isolated from ÔAglianico del VultureÕ grape must. Methods and Results:The restriction analysis of 18S rDNA allowed the identification of strains at the species level, which were predominantly Hanseniaspora uvarum. The RAPD analysis and the evaluation of technological traits, such as the metabolic and enzymatic activities, were useful to evaluate the polymorphism of this species. Conclusions: The RAPD analysis clustered the wild H. uvarum strains in four main genetic groups and a very high phenotypic variability confirmed this genetic polymorphism. The technological variables, which determined the strain biodiversity differed significantly, demonstrating that these technological traits are strain dependent. A certain correlation was found between the strain behaviour and its isolation zone, indicating the influence of the environment on the genetic patrimony of the population. Significance and Impact of the Study: The genetic and technological biodiversity recorded among H. uvarum wild strains represents the basis for organizing a collection of apiculate strains exhibiting oenological characteristics at different levels, such as high/low production of secondary compounds, and, therefore, potentially useful for a selection programme.

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In Mexico there are different alcoholic beverages produced from agave juices from different agave plants, which are cooked, fermented and distilled. For tequila production only Agave tequilana is allowed. In this study we compared yeast strains of different species from different origin (agave and grape juice) for parameters of technological interest, such as SO 2 and copper resistance, ethanol tolerance and enzymatic activities. All agave strains were found to be more resistant to SO 2 and agave non-Saccharomyces yeasts were more tolerant to ethanol, whereas grape strains exhibited positive results for b-glucosidase and b-xylosidase activities. As regards fermentations of Agave tequilana juice with ethanol added at different concentrations, only agave Saccharomyces strains were more tolerant to ethanol than grape strains.

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