Effects of Torulaspora delbrueckii and Metschnikowia pulcherrima on Oenococcus oeni and malolactic fermentation

Identifier:  TDX:3194

Handle: https://hdl.handle.net/20.500.11797/TDX3194

Authors:  Balmaseda Rubina, Aitor

Abstract:
Oenococcus oeni is the main agent responsible of wine malolactic fermentation (MLF). This lactic acid bacterium overcomes difficult and harsh wine conditions in order to finish MLF, which usually takes place after alcoholic fermentation, traditionally undergone inoculating Saccharomyces cerevisiae. In this sense, the current interest in non-Saccharomyces yeasts open a new scenario where the interactions between them and O. oeni are still unknown. The aim of this thesis was to evaluate the effects of non-Saccharomyces, particularly Torulaspora delbrueckii and Metschnikowia pulcherrima, on O. oeni and MLF. Firstly, these effects were studied under real winemaking conditions, where the use of non-Saccharomyces reduced the MLF duration and modulated the wine organoleptic attributes. From those, polyphenolic composition was enhanced by the use of T. delbrueckii. Then, the performance of MLF was evaluated under lees of different yeast species, resulting an improvement in those wines with T. delbrueckii lees. From this, the use of mannoproteins was related with a useful metabolism of O. oeni to face wine conditions. The genes related with this metabolism responded to these conditions and consumption of mannoproteins was increased in wines with the highest mannoprotein content. Also, a combined omic approach was used to identify those molecular changes activated in O. oeni by non-Saccharomyces. These changes were mainly related with amino acid and carbohydrate metabolisms. Moreover, a complex metabolism of amino acids affected by non-Saccharomyces was observed, in which peptides are the key nitrogen compound in O. oeni. The results of this thesis contribute to better understand the general impacts of non-Saccharomyces in O. oeni and how the bacterium respond to those changes at molecular level. In addition, this thesis points the main key elements and metabolisms to consider in the selection of suitable yeast- O. oeni strain tandem for winemaking.