Identifier: TDX:2961
Authors: Lleixà Daga, Jéssica
Abstract:
Populations of yeasts, fungi and bacteria coexist on grape berry surface. Some species belonging to these yeasts, also known as non-Saccharomyces, are of oenological interest. In this thesis, the effects of different biotic and abiotic factors on fungal and bacterial communities during alcoholic fermentation have been studied, emphasizing its effect on non-Saccharomyces yeasts. Therefore, the health status of the grape together with nitrogen and sugar concentrations of the must on the fermentation process and the microbiota has been evaluated. The results show that health status of the grape defines the microbial communities along the alcoholic fermentation. Moreover, nitrogen has demonstrated to be the decisive nutrient for fermentation success. On the other hand, the fermentations and wines obtained using Hanseniaspora vineae, a non-Saccharomyces yeast of oenological interest, and Saccharomyces cerevisiae have been analysed. H. vineae’s wines exhibited a more fruity and flowery aroma thanks to 2-phenetyl acetate production. Additionally, it has been observed the presence of nitrogen catabolite repression(NCR) mechanism in H. vineae considering the expression profile of AGP1, GAP1, MEP2 and PUT2 genes and the nitrogen consumption. Finally, genotypic and phenotypic diversity of Brettanomyces bruxellensis, a non-Saccharomyces spoiler wine yeast, from Catalonia has been evaluated. The different B. bruxellensis isolates distributed according to the isolation region and exhibited a variable SO2 tolerance and a great ability to produce volatile phenols.
Repositori URV