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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Aims: To develop a real-time polymerase chain reaction (PCR) method for rapid detection and quantification of Oenococcus oeni in wine samples for monitoring malolactic fermentation. Methods and Results: Specific primers and fluorogenic probe targeted to the gene encoding the malolactic enzyme of O. oeni were developed and used in real-time PCR assays in order to quantify genomic DNA either from bacterial pure cultures or wine samples. Conventional CFU countings were also performed. The PCR assay confirmed to be specific for O. oeni species and significantly correlated to the conventional plating method both in pure cultures and wine samples (r ¼ 0AE902 and 0AE96, respectively). Conclusions: The DNA extraction from wine and the real-time PCR quantification assay, being performed in ca 6 h and allowing several samples to be concurrently processed, provide useful tools for the rapid and direct detection of O. oeni in wine without the necessity for sample plating. Significance and Impact of the Study: Rapid quantification of O. oeni by a real-time PCR assay can improve the control of malolactic fermentation in wines allowing prompt corrective measures to regulate the bacterial growth.

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.