Metabolic diversity of Saccharomyces cerevisiae strains from spontaneously fermented grape musts Patrizia Romano, Marisa Caruso*, Angela Capece, Gabriella Lipani, Margherita Paraggio and Concetta Fiore Dipartimento di Biologia, Difesa e Biotecnologie Agroforestali, Universita ` degli Studi della Basilicata, Campus Macchia Romana, 85100 Potenza, Italy *Author for correspondence: Tel.: +39 971 205 576/686, Fax: +39 971 205 503/686, E-mail: romano@unibas.it Received 10 September 2002; accepted 27 November 2002 Keywords: Saccharomyces cerevisiae, secondary compounds, tetrad analysis, wine fermentation, yeast selection Summary One hundred and fifteen Saccharomyces cerevisiae strains from Aglianico del Vulture, a red wine produced in Southern Italy, were characterized for the production of some secondary compounds involved in the aroma and taste of alcoholic beverages. The strains exhibited a uniform behaviour in the production levels of n-propanol, active amyl alcohol and ethyl acetate, whereas isobutanol, isoamyl alcohol and acetaldehyde were formed with a wide variability. Only five strains produced wines close to the reference Aglianico del Vulture wine for the traits considered. Of these, two strains were selected, underwent to tetrad analysis and the single spore cultures were tested in grape must fermentation. The progeny of one strain showed a significant metabolic variability, confirming the necessity to test starter cultures for the segregation of traits of technological interest. Our findings suggest the selection of specific strains for specific fermentations as a function of the vine variety characteristics in order to take the major advantage from the combination grape must/S. cerevisiae strain. Introduction Wine flavour is the result of a complex combination of components that give a distinctive finger to each final product. Yeast metabolism makes an important contri- bution to flavour and nowadays commercial selected strains of Saccharomyces cerevisiae are in widespread use for winemaking. Although these commercial strains have often been isolated by prestigious wine research institutes and characterized for their technological traits, their use for production of wine of different variety and origin could be inappropriate, due to a potential uniformity of aromatic characteristics in the final product. In fact, collections of S. cerevisiae strains from natural fermentations have demonstrated the existence of a strong technological variability within this species (Ran- kine 1968; Soufleros & Bertrand 1979; Cabrera et al. 1988; Giudici et al. 1990; Romano & Suzzi 1993; Romano et al. 1994; Henschke 1997; Pretorius 2000). Each fermentation seems to have its own population of different S. cerevisiae strains (Frezier & Dubourdieu 1992; Querol et al. 1992; Schu¨tz & Gafner 1993; Polsinelli et al. 1996), which contribute to the chemical composition and sensory qualities of the resulting wine (Lurton et al. 1995). Therefore, the different strain- specific pattern can be presumed as being typical for each fermentation (Romano 1998). Aglianico del Vulture is an ancient grape variety cultivated in the mountain Vulture area, in the Basilicata region(SouthernItaly).Itisutilizedtoproducearedwine with typical organoleptic characteristics, traditionally produced by spontaneous fermentation of grape juice. In this paper, we present a characterization of Aglianico-autochtonous strains by means of metabolic profile determination. The study has been focused on the production of some secondary compounds involved in the aroma and taste of alcoholic beverages, such as higher alcohols, carbonyl compounds, acetic acid and esters. Materials and methods Strain isolation This study was carried out in 1999 on grapes harvested in 13 vineyards, located in the zone of Aglianico del Vulture production. From 10 vines per vineyard 500 g of grapes per vine were collected in separate plastic bags. The grape clusters were chosen healthy and bird- damaged alike. In the laboratory, the samples were crushed under aseptic conditions in the original collec- tion plastic bags. The musts obtained were transferred to sterile flasks and underwent spontaneous fermenta- tion at 25 °C. Appropriate dilutions of wines at the end World Journal of Microbiology & Biotechnology 19: 311–315, 2003. 311 Ó 2003 Kluwer Academic Publishers. Printed in the Netherlands.