## 1 Introduction  
In the last century, _Saccharomyces_ was the only genus of yeasts used in wine pillars and, although grapes have a great diversity of species and yeasts strains, the dominance of _Saccharomyces cerevisiae_ during alcoholic fermentation was expected and desired. Traditionally, the use of _Saccharomyces_ yeasts together with non-_Saccharomyces_ species during alcoholic fermentation influences the final composition of the wine. Thus, the contribution to the final quality of the wine of some yeast strains that acted during fermentation can be negative, because in some cases increases in ethyl acetate, volatile acidity, and acetaldehyde are observed, among others [1, 2]. Conversely, they may present a positive contribution, increasing some desirable metabolites, such as acetate esters [3], which generally provide greater organoleptic complexity. Different genera and species of non-_Saccharomyces_ yeasts are now emerging to improve the winemaking process and the quality and differentiation of wines. Thus, many research topics are based on the use of non-_Saccharomyces_ species to improve wine quality and aromatic profile or to modulate the composition of the wine [4, 5]. Among the non-_Saccharomyces_ yeasts, the most studied genera are _Candida_, _Metschnikowia_, _Pichia_, _Torulaspora_, _Starmerella_, and _Lachancea_, because they help improve the organoleptic characteristics of wines, such as color, aroma, and sensory characteristics. It is described that, when non-_Saccharomyces_ yeasts are added in the early stages of grape must fermentation, the aroma wine quality improves because of the resulting metabolic products, such as terpenoids, esters, higher alcohols, glycerol, acetaldehyde, and organic acids [4; 5]. [PERSON] et al. [6] reviewed the use of different non-_Saccharomyces_ yeasts in winemaking and, in addition to this aromatic improvement, they noted other benefits, such as a reduction in the undesirable microflora, alcohol degree, and the amounts of sulfur dioxide, hydrogen sulfide, acetaldehyde and copper [6]. Therefore, because non-_Saccharomyces_ yeasts produce wines with many distinctive characteristics, there are progressively more commercially available for different yeast species, such as _T. delbrueckii_, _M. pulcherrima_, and _P. kluyveri_. The literature currently shows that many studies that have used non-_Saccharomyces_ yeasts during alcoholic fermentation to produce different types of wines. However, few studies have examined the effect of these yeasts on the quality of sparkling wines, such as cava. The most characteristic note of these appreciated wines is their bubbles, generated in a second fermentation, which provides many other distinctive organoleptic properties. This second fermentation is not easy because, once the first fermentation is complete, the yeasts face a hostile environment due to high alcohol content (around 11%), high pressure (5-6 bars), lack of nutrients, low pH, and the presence of SO\({}_{2}\). Furthermore, the yeast must be able to ferment at low temperatures and must have both a good flocculation and autolytic ability. As the _Saccharomyces_ genus meets all of these requirements, it has been the most commonly used yeast for this purpose. However, recently, other species have been also studied, such as _Schizosaccharomyces pombe_[1], which shows a better adaptation to these specific circumstances, allowing the transformation of malic acid into ethanol, significantly reducing the levels of biogenic amines, and presenting the ability to ferment the sparkling base wine to dryness without producing aromatic defects [7; 8; 9]. _T. delbrueckii_ is another non-_Saccharomyces_ yeast that is able to carry out the second fermentation with interesting results because it enhances the sensory profile of the sparkling wine obtained compared to that provided by _S. cerevisiae_. This is due to a higher production of esters with subsequent high scores for some positive aromatic descriptors [10].