Influence of organic viticulture on non-Saccharomyces wine yeast populations

This study evaluated the population dynamics ofnon-Saccharomyces biota during spontaneous fermentation of organic musts. Non-Saccharomyces yeasts were found tobe present at high levels during all fermentations. A total of 543 yeast colonies were isolated, 190 from Lysine-Medium (LM) agar, 254 from Wallerstein Laboratory Nutrient(WLN) agar and 99 from YPD agar. To estimate yeast population dynamics during spontaneous fermentation a genotypic approach was applied. PCR-RFLP of the ITS1-5.8S rDNA-ITS2 region and sequence determination of theD1/D2 region of the 26S rRNA gene enabled identificationof the yeast isolates at the species level. Hanseniasporauvarum, Metschnikowia fructicola and Candida zemplinina predominated, while Issatchenkia terricola, Issatchenkiaorientalis and Pichia sp. were identified with a lower frequency. Hanseniaspora uvarum, M. fructicola and C.zemplinina represented 43%, 31% and 11% of the total non-Saccharomyces population isolated, respectively. Someyeast isolates were shown to be closely related toHanseniaspora spp. and Candida spp. on the basis of the D1/D2 sequences. Based on those results, the coexistenceof different Hanseniaspora and Pichia species in grape musts was supposed, and their complete identification was achieved using additional molecular markers. Moreover,strain typing and differentiation was carried out by RAPD-PCR. High strain polymorphisms were observed in thedifferent species. For some strains, appreciable properties were demonstrated both in vitro by the API-ZYM test and in must. In must microvinification some strains showedgood fermentation performances, low production of acetic acid and a partial capability to degrade malic acid.[...]