Dr Daniela Barbera, for help with the triangle tests. We thank Dr Antonio Sparacio and the oenologist Salvatore Sparla for help with the Merlot and Nero d'Avola grapes. We also acknowledge the "Valle dell'Acate" winery for help with the Frappato grapes. Funds for this work were provided through an intramural grant of the IRVO

Significance and Impact of the Study: In recent years, interest is growing for wine production by nonSaccharomyces yeasts, both in research and in the industry. This study describes the yeast population of the grapes in a small-secluded island in the Mediterranean Sea, useful site for the search of new strains. Evaluation of fundamental oenological characters identifies potential best yeasts to assay in experimental vinifications. We also describe, for the first time, 14 new colony morphologies on WL Nutrient Agar, culture medium used to monitor the yeast population dynamics. AbstractWe isolated, identified and characterized yeast strains from grapes, and their fermented musts, sampled in the small island of Linosa, where there are no wineries and therefore the possibility of territory contamination by industrial strains is minimal. By traditional culture-dependent methods, we isolated 3805 colonies, distinguished by molecular methods in 17 different species. Five hundred and fortyfour isolates were analysed for the main oenological characteristics such as fermentative vigour with and without sulphites, sugar consumption and production of alcohol, volatile acidity, hydrogen sulphide, glycerol and b-glucosidase. This analysis identified Kluyveromyces marxianus (seldomly used in winemaking) as the most interesting candidate yeast for the production of innovative wines.

An increasing interest in novel wine productions is focused on non-Saccharomyces yeasts due to their potential in improving sensory profiles. Although Kluyveromyces marxianus has been originally isolated from grapes and its enzymatic activities are used in oenology, rarely it has been used as co-starter. The K. marxianus Km L2009 strain has been characterized here and selected as a co-starter both at laboratory- and winery-scale fermentation. The Km L2009 strain showed growth of up to 40 (mg/L) of sulfites and 6% (v/v) of ethanol. Gas chromatographic analysis demonstrates that wines produced by mixed fermentation contain remarkably higher quantities of free monoterpenes and aliphatic esters than wines produced only by commercial strains of Saccharomyces cerevisiae. Differences in the volatile organic compound composition produced sensorially distinct wines. In light of these results, it is possible to state that even within the K. marxianus species it is possible to select strains capable of improving the aromatic quality of wines.