Abstract
Wine production depends on the fermentation process performed by yeasts, especially (but not solely) strains of the species Saccharomyces cerevisiae, which is a technique that has been practiced from the Middle Ages till modern days. Selecting indigenous starters offers a beneficial technique to manage alcoholic grape juice fermentation, conserving the particular sensory qualities of wine produced from specific regions. This paper investigated yeast biodiversity of four grape varieties (Carignan, Syrah, Grenache, and Aswad Karesh) grown in the pedoclimatic western semi-desert Bekaa Valley. Further research identified, characterized, and selected strains with the most industrial wine interest and economic value to Lebanon. By using molecular methods and by the ITS PCR analysis, the isolates belonging to the Saccharomyces and non-Saccharomyces genus were identified. These isolates taken from four varieties were further characterized by amplification with Interdelta and δ12/δ21 primer pairs, permitting the identification of 96 S. cerevisiae strains. Forty-five genomically homogenous groups were classified through the comparison between their mtDNA RFLP patterns. Based on physiological characterization analysis (H2S and SO2 production, killer phenotype, sugar consumption, malic and acetic acid, etc.), three strains (NL28629, NL28649, and NL28652) showed interesting features, where they were also vigorously fermented in a synthetic medium. These strains can be used as a convenient starter for typical wine production. In particular, Carignan and Syrah had the highest percentage of strains with the most desirable physiological parameters.
Highlights
The transformation of grape juice into wine is basically a fermentation process historically carried out by indigenous yeasts and considered to be the most economically significant of all biotechnologies [1]
The PCR amplification showed that all the isolates exhibiting PCR-RFLP patterns with size 370/360/110 bp for Hinf I and 320/230/170/120 bp for Hae III corresponded to S. cerevisiae
There is a prevalent assumption that spontaneous alcoholic fermentation, generated by indigenous microflora yeast, is determined by each specific vineyard, and it provides a particular characteristic and quality of each wine
Summary
The transformation of grape juice into wine is basically a fermentation process historically carried out by indigenous yeasts and considered to be the most economically significant of all biotechnologies [1]. As the significance of S. cerevisiae in wine-making has long been acknowledged, the use of commercial strains of yeast cultures in fermentation becomes one of the most prevalent techniques to assure a consistent product and to prevent wine spoiling This approach might establish a progressive substitution of local microflora and a corresponding diminution or lack of several beneficial and distinctive organoleptic properties of natural or spontaneous alcoholic fermentation. We investigated: (i) the biodiversity of indigenous yeast microflora at the species level hosted by 12 distinct grape varieties remotely grown in vineyards residing in the Bekaa–Château Kefraya domain (Lebanon), (ii) the molecular identity of genomically different yeast strains, (iii) the physiological characteristics of selected strains such as H2 S and SO2 production, killer phenotype, sugar consumption, acids present, etc. We investigated: (i) the biodiversity of indigenous yeast microflora at the species level hosted by 12 distinct grape varieties remotely grown in vineyards residing in the Bekaa–Château Kefraya domain (Lebanon), (ii) the molecular identity of genomically different yeast strains, (iii) the physiological characteristics of selected strains such as H2 S and SO2 production, killer phenotype, sugar consumption, acids present, etc. (iv) the differences among the 4 varieties regarding the most desirable hosted strains, (v) and the best grape varieties that must be included at higher percentage during wine preparation
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