D. Oliva

Presence of Candida zemplinina in Sicilian Musts and Selection of a Strain for Wine Mixed Fermentations

The purpose of this work was to investigate the presence of C. zemplinina yeasts in Sicilian musts and grapes and to identify strains of oenological interest. We report on the taxonomical reclassification of Candida yeast isolates from Sicilian musts and on the selection of one strain of oenological interest (Cz3), based on mixed micro-fermentation experiments in sterile Nero d’Avola musts. Our results show that Candida zemplinina is abundant in Sicilian grapes and musts, and that the Cz3 strain is suitable for Candida zemplinina/Saccharomyces cerevisiae mixed fermentations. The higher glycerol content and the lower ethanol level stood out as the most promising features of the wines obtained upon sequential inoculation of the Cz3 and (S. cerevisiae) NDA21 yeast starters. We therefore have isolated a Sicilian Cz strain endowed with very promising features for the future development of mixed fermentation protocols.

Biodiversity of indigenous Saccharomyces populations from old wineries of south-eastern Sicily (Italy): preservation and economic potential.

In recent years, the preservation of biodiversity has become an important issue. Despite much public discussion, however, current practices in the food industry seldom take account of its potential economic importance: on the contrary, the introduction of industrialized agriculture practices over large areas has often resulted in a dramatic reduction in biodiversity. In this paper, we report on the remarkable degree of biodiversity in the wine yeast populations naturally present in a small area of Sicily (Italy) where traditional (non-industrial) winery practices are still in place. Out of more than 900 Saccharomyces yeast isolates recovered from late spontaneous fermentations, we detected at least 209 strains. Most interestingly, when evaluated at the fermentation and technological level, a number of isolates were found to be superior to industrial yeast strains. Out of a selected group, isolates from two strains were used for experimental fermentations in a winery environment and the quality of the wines produced was assessed at the technological, quality and sensory levels. Given that the characteristics of the wines produced were found to be industrially appealing, the study demonstrated the economic potential of preserving the patrimony of Sicilian yeast biodiversity and highlighted the importance of maintaining traditional wine making practices.

Analysis of non‐Saccharomyces yeast populations isolated from grape musts from Sicily (Italy)

Aims:  The aim of this study was to identify the non‐Saccharomyces yeast populations present in the grape must microflora from wineries from different areas around the island of Sicily.

Candida zemplinina for production of wines with less alcohol and more glycerol

We developed a new protocol for winery mixed fermentations, using the selected Candida zemplinina yeast strain Cz3. The results of a two-year study, in which red musts (Merlot in 2010; Merlot, Nero d’Avola and Frappato in 2011) were inoculated with Cz3, is discussed. These wines were compared with wines obtained by inoculation with commercial Saccharomyces cerevisiae yeast strains (NDA21 and AR06 in 2010; NDA21 in 2011), or with those obtained by spontaneous fermentation (only in 2011). The inoculation of Cz3 always resulted in a two-phase fermentation: the first phase was driven by the C. zemplinina strain, while the second was dominated by the indigenous S. cerevisiae yeasts coming from the grapes and/or the winery. In both years the Cz3 wines contained less alcohol and more glycerol than those made with the commercial yeast strains or those obtained by spontaneous fermentation. Triangle tests showed that a sensorial difference between wines could only be achieved through the utilisation of Cz3.

A method to discriminate between the Candida stellata and Saccharomyces cerevisiae in mixed fermentation on WLD and lysine agar media.

This paper presents a simple method to distinguish between Candida stellata and Saccharomyces cerevisiae yeasts during microbiological analyses. The method is based on differential yeast growth on a medium containing cycloheximide and a medium containing lysine as only nitrogen source (lysine agar). The cycloheximide resistance of 45 yeast strains belonging to Candida stellata, Hanseniaspora uvarum, Hanseniaspora guilliermondii, Metschnikowia pulcherrima, Torulaspora delbrueckii, Zygosaccharomyces bailii, Kluyveromyces thermotolerans and Zygoascus hellenicus, and 14 strains of Saccharomyces cerevisiae and Saccharomyces bayanus on WL nutrient agar, was assayed. Cycloheximide resistance is characteristic of the species H. uvarum, H. guilliermondii and Z. hellenicus, while for the other yeasts it depends on the strain and the concentration of cycloheximide used. Two mg/L of cycloheximide allows selective counting of a strain of C. stellata (Cs3) compared to one of the sensitive S. cerevisiae strain (NDA21). Similar results can be obtained on lysine agar, but counts are reliable only with the additional spreading of a monolayer of Saccharomyces cells. The different cycloheximide resistance of C. stellata and S. cerevisiae can be used in the microbiological analysis of mixed cultures to monitor the individual growth of the two yeast species. This method can be applied to the study of mixed fermentations with other non-Saccharomyces species. The modified use of lysine agar is useful to a certain extent in the distinction of multistarter yeasts from the indigenous yeasts.

Isolation, identification and oenological characterization of non-Saccharomyces yeasts in a Mediterranean island

We 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 forty‐four 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 β‐glucosidase. This analysis identified Kluyveromyces marxianus (seldomly used in winemaking) as the most interesting candidate yeast for the production of innovative wines.

Increasing voltage gradient electrophoresis of DNA

We developed a method which allows electrophoretic fractionation of DNA in an agarose matrix according to an increasing current gradient, using a previously designed [R. Barbieri, V. Izzo, M.A. Costa, G. Giudice, G. Duro, Anal. Biochem. 212 (1993) 168; M.R. Asaro, V. Izzo, R. Barbieri, J. Chromatogr. A 855 (1999) 723] voltage gradient apparatus. This method allows the separation of different DNA fragments by increasing the distances of the components fractionated in the gel, revealing small differences in the length of different DNA components.