The biogenic amine-producing capability of several Oenococcus oeni strains, originally isolated from different Italian wines, was determined. The amine-producing capability was quali-quantitatively variable among the strains: out of the 44 strains investigated under optimal growth conditions, more than 60% were able to produce histamine, at concentrations ranging from 1.0 to 33 mg/L, and about 16% showed the additional capability to form both putrescine and cadaverine, to different extents and variable relative proportions. The amine-producing behavior of the strains was confirmed under stress culture conditions, while performing malolactic fermentation. In wine, one randomly chosen strain was very effective in forming putrescine from ornithine. The formation of putrescine from arginine by some strains has been also demonstrated. Consequently, O. oeni can really and significantly contribute to the overall biogenic amine content of wines. Practical consequences of these findings are discussed.

Numerous studies, based on different molecular techniques analyzing DNA polymorphism, have provided evidence that indigenous Saccharomyces cerevisiae populations display biogeographic patterns. Since the differentiated populations of S. cerevisiae seem to be responsible for the regional identity of wine, the aim of this work was to assess a possible relationship between the diversity and the geographical origin of indigenous S. cerevisiae isolates from two different Italian wine-producing regions (Tuscany and Basilicata). For this purpose, sixty-three isolates from Aglianico del Vulture grape must (main cultivar in the Basilicata region) and from Sangiovese grape must (main cultivar in the Tuscany region) were characterized genotypically, by mitochondrial DNA restriction analysis and MSP-PCR by using (GTG)5 primers, and phenotypically, by determining technological properties and metabolic compounds of oenological interest after alcoholic fermentation. All the S. cerevisiae isolates from each region were inoculated both in must obtained from Aglianico grape and in must obtained from Sangiovese grape to carry out fermentations at laboratory-scale. Numerical analysis of DNA patterns resulting from both molecular methods and principal component analysis of phenotypic data demonstrated a high diversity among the S. cerevisiae strains. Moreover, a correlation between genotypic and phenotypic groups and geographical origin of the strains was found, supporting the concept that there can be a microbial aspect to terroir. Therefore, exploring the diversity of indigenous S. cerevisiae strains can allow developing tailored strategies to select wine yeast strains better adapted to each viticultural area.

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Quercetins, vitisin A and hydroxytyrosol are phenolic compounds possessing several positive properties to human health. This paper refers on the possible effects of two wine yeast species, Saccharomyces cerevisiae and Starmerella bacillaris (synonym Candida zemplinina) on the accumulation of these compounds in experimental Sangiovese wines. A single lot of Sangiovese grapes was fermented by S. cerevisiae alone or by sequential inoculum of C. zemplinina and S. cerevisiae under two aeration conditions. The accumulation of quercetin and its glycosides resulted only influenced by must aeration. However, yeast species occurring in the fermentative process affected the relative abundances among the different forms of quercetin. Vitisin A contents were higher in wines produced in the presence of C. zemplinina. Finally, higher concentrations of hydroxytyrosol and tyrosol were found in wines produced by S. cerevisiae alone under non-aerated condition. The fermentation of different Sangiovese grape musts carried out by the assayed S. cerevisiae strain pointed out that slow fermentation kinetics lead to higher levels of hydroxytyrosol and tyrosol. The study underlines the role of yeast species in determining the accumulation of bioactive compounds in Sangiovese wine.

Different Saccharomyces cerevisiae strains are simultaneously or in succession involved in spontaneous wine fermentations. In general, few strains occur at percentages higher than 50% of the total yeast isolates (predominant strains), while a variable number of other strains are present at percentages much lower (secondary strains). Since S. cerevisiae strains participating in alcoholic fermentations may differently affect the chemical and sensory qualities of resulting wines, it is of great importance to assess whether the predominant strains possess a “dominant character.” Therefore, the aim of this study was to investigate whether the predominance of some S. cerevisiae strains results from a better adaptation capability (fitness advantage) to the main stress factors of oenological interest: ethanol and temperature. Predominant and secondary S. cerevisiae strains from different wineries were used to evaluate the individual effect of increasing ethanol concentrations (0-3-5 and 7% v/v) as well as the combined effects of different ethanol concentrations (0-3-5 and 7% v/v) at different temperature (25–30 and 35°C) on yeast growth. For all the assays, the lag phase period, the maximum specific growth rate (μmax) and the maximum cell densities were estimated. In addition, the fitness advantage between the predominant and secondary strains was calculated. The findings pointed out that all the predominant strains showed significantly higher μmax and/or lower lag phase values at all tested conditions. Hence, S. cerevisiae strains that occur at higher percentages in spontaneous alcoholic fermentations are more competitive, possibly because of their higher capability to fit the progressively changing environmental conditions in terms of ethanol concentrations and temperature.

Putrescine, the most abundant biogenic amine in wine, was proved to be produced by Oenococcus oeni strains in wine not only from ornithine but also from arginine. In this case, putrescine may originate from strains possessing the complete enzyme system to convert arginine to putrescine or by a metabiotic association, with an exchange of ornithine, between strains capable of metabolizing arginine to ornithine but unable to produce putrescine and strains capable of producing putrescine from ornithine but unable to degrade arginine. Putrescine production by this metabiotic association occurred once the malolactic fermentation was completed, whereas conversion of ornithine to putrescine by a single culture of the ornithine decarboxylating strain concurred with the degradation of malic acid. Moreover, in the former case, putrescine formation proceeded more slowly than in the latter. Metabiosis may play an important role in the accumulation of putrescine in wine, arginine being one of the major amino acids found in wine.

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Abstract:Moderate wine consumption is associated with human health benefits (reduction of cardiovascular risk and neurodegenerative diseases, decrease of onset of certain cancers) attributed to a series of bioactive compounds, mainly polyphenols, with antioxidant power capable of counteracting the negative action of free radicals. Polyphenols are naturally present in the grapes, but an additional amount originates during winemaking. The aim of this work was to assess the ability of four commercial and two indigenous Saccharomyces cerevisiae strains to produce bioactive compounds (tyrosol, hydroxytyrosol, tryptophol, melatonin and glutathione) during alcoholic fermentation. In order to exclude the fraction of antioxidant compounds naturally occurring in grapes, the strains were inoculated in a synthetic must. At the end of fermentation the bioactive compounds were analysed by High-Performance Liquid Chromatography, while antioxidant activity was measured by 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. Moreover, freeze-dried samples, originating from the experimental wines, were used to perform ex-vivo assays on cultured cells (RAW 264.7 murine macrophages) with the aim to evaluate their antioxidant and anti-inflammatory activities. The results indicated that the production of the considered bioactive compounds is a strain-specific property; therefore, the different yeast strains utilized during fermentation have different capabilities to modify the antioxidant and anti-inflammatory properties of the wine.