Interactions between Non-Saccharomyces species in alcoholic fermentation

Identifier:  TFG:3031

Handle: https://hdl.handle.net/20.500.11797/TFG3031

Authors:  González Fornell, José Manuel

Abstract:
Previous researches have demonstrated that a strain of Lachancea thermotolerans (Lt2) and a strain of Torulaspora delbrueckii (Td5) inhibit the fermentations and reduce the growth of a Saccharomyces cerevisiae’s strain (ScR) during the alcoholic fermentation. Relying on this result, the verification that is wanted to achieve, is to see if these strains inhibit the fermentation and the growth of Non-Saccharomyces too. In order to do that, sequential fermentations were made in synthetic most using Td5 and Lt2, varying the inoculations’ order. In some of these fermentations, the first strain remained inoculated as the second strain was inoculated. In the others of these fermentations, the first strain inoculated was removed before inoculating the second strain. Using this methodology, it was corroborated that the possible inhibition was happening because of a cell-cell contact or because of a specific molecule’s secretion. In order to control the fermentations, several analyses were performed, not only of the process’ kinetic of density but also of the population’s evolution, throw the use of differential medias and quantitative PCR (qPCR) with specific primer. Besides, the evolution of the consume of the media’s nitrogen was also studied. Performing these analyses and examining the results, it could be concluded that Lt2 and Td5 produce a growth inhibition of each other in the sequential mixed fermentations. However, it is producing a synergy in the fermentation, making it faster. In other matters, it was observed that what was being produced was an inhibitory fermentation effect in the sequential filter fermentations. This effect was higher by Td5 than Lt2. Nevertheless, the yeasts growth in these fermentations wasn’t inhibited despite being affected.