Interactions between non-saccharomyces yeast during alcoholic fermentation of wine

Identifier:  TFG:2943

Handle: https://hdl.handle.net/20.500.11797/TFG2943

Authors:  Javierre Ortin, Aaron

Abstract:
In previous research, interactions have been observed between a strain of Lachancea Thermotolerans (Lt2) and a strain of Torulaspora delbrueckii (Td5) when they share culture medium. In view of the behaviour of both species, we want to determine the mechanism of interaction between Td5 and Lt2 strains. To this end, sequential fermentations and mixed fermentations (co-inoculations) were carried out in synthetic must with both strains. In one of the sequential fermentations, Td5 was maintained at the time of inoculation of Lt2. In addition, 100 mg/L of assimilable nitrogen (YAN) was added. In the other sequential fermentations, Td5 was removed before inoculation of Lt2 and the addition of assimilable nitrogen. The purpose of these methodologies was to check whether the fermentation problems observed were due to a lack of nutrients, to the secretion of some molecule or to the combined action of both. Fermentations were analysed by measuring fermentation kinetics, through must density analysis, and by measuring the evolution of the yeast population, through optical density, plate seeding and quantitative PCR (qPCR). The results obtained were similar to the previous studies, with growth inhibition between strains being observed when co-inoculated in a 1:1 ratio and in sequential filtered inoculations. However, a synergy is observed in sequential fermentation when both yeasts maintain contact. Analyzing the results, it is concluded that the lack of assimilable nitrogen is not the cause of fermentation inhibition, so further research is needed to understand the mechanism of inhibition.