Genetic and technological characterization of indigenous Saccharomyces cerevisiae strains isolated from 'Merwah' wine (Lebanon)

In order to gain deeper knowledge of genetic diversity and population structure of Lebanese indigenous Saccharomyces cerevisiae strains, 202 isolates were collected during spontaneous alcoholic fermentation of eight must/wine samples of ‘Merwah’, native cultivar, over two consecutive years in a traditional winery in Mount Lebanon. The isolates were identified as belonging to the S. cerevisiae species based on their morphology and preliminary analysis of the ITS 1-4 region sequence. They were then characterized at strain level by analysis of the interdelta regions, and genotyped using 12 microsatellite markers. In addition, strains were subjected to test phenotypic sulfite resistance and chromosomal translocation on SSU1gene by means of PCR. To select the most potential yeast starter strains, micro-fermentations were carried out for 22 S. cerevisiae strains that were selected as representatives of the population. Based on the main technological parameters (i.e., residual sugar, fermentative vigour, lowest sulphur production and acetic acid), three yeast strains were selected as candidates for pilot-scale fermentation at the winery. These strains were subjected to chemical and sensorial analysis for selecting a S. cerevisiae strain, adequate to produce ‘Merwah’ wine. This study will devote to test the drying attitude of the selected strain; make industrial wine using the selected dry strain ad a starter; and verify the quality of the resulting wine.