EVOLUTION AT THE MICROFERMENTER LEVEL OF THE GROWTH DYNAMICS OF Saccharomyces cerevisiae AND Starmella bacillaris YEASTS WITH POTENTIAL FOR USE IN WINEMAKING AT THE PIETROASA WINERY

Abstract

The grape surface hosts a complex community of yeast Saccharomyces and non-Saccharomyces species responsible for spontaneous alcoholic fermentation in wine industry. The yeast strains used for this study were isolated from 'Tămâioasă Românească’ and 'Busuioacă de Bohotin’ grape varieties from Pietroasa vineyard, and the isolates were identified through a molecular method. Identification of yeast strains through the BLASTn analysis of the 5.8S-ITS region revealed that PFE5 strain showed the best sequence match to Saccharomyces cerevisiae (98% similarity) and PFE15 strain to Starmerella bacillaris (99.78% similarity), respectively. In this first micro-pilot study, the differences between Sacharomyces and non-Saccharomyces yeasts in batch (for Starmella bacillaris) and fed-batch fermentation system (for S. cerevisae) and how these regimes influence the culture growth were assessed. The applied fed-batch process was capable for producing two times more S. cerevisae yeast biomass than Starmella bacillaris through a batch process. In addition, the yield of S. cerevisiae converting the substrate into biomass was 42.3%, almost double compared to the yield of Starmella bacillaris. Moreover, the cell wet weight (WCW) for S. cerevisae was 32.5 g/L and for Starmella bacillaris 15.35 g/L, respectively. Both yeast biomass will be used at Pietroasa winery for inoculation separately or mixed as co-culture for 'Tămâioasă Românească’ and 'Busuioacă de Bohotin’ grape juice.