## 4 Discussion  
The renewed interest in non-_Saccharomyces_ yeasts has led to the industrial production of selected cultures for winemaking. Currently, _T. delbrueckii_ is the first non-_Saccharomyces_ species produced for this purpose, and the most commercially available active dry yeast. The ability of _S. cerevisiae_ to compete with other non-_Saccharomyces_ yeasts and to dominate wine fermentation is well established. Moreover, _T. delbrueckii_ generally has less fermentation vigor and a lower growth rate than _S. cerevisiae_ under usual wine fermentation conditions [10; 12], and this behavior may suggest a difficulty in dominating must fermentation in the presence of _S. cerevisiae_ yeasts [31]. However, under the conditions tested (two days of sequential inoculation), the _T. delbrueckii_ DiSVA 130 strain did not seem to be affected by the presence of _S. cerevisiae_ DiSVA 709. The results of the fermentation kinetics agreed with previous studies [7; 32], reporting a lower ethanol production in the trials where the musts were inoculated with _T. delbrueckii_ yeast, although no statistical differences were seen between commercial _T. delbrueckii_ and the selected native strain. Regarding the biocontrol action, [PERSON] et al. [19] reported noticeable bioprotectant and antioxidant effects of _T. delbrueckii_ inoculated at the beginning of the white winemaking process, while [PERSON], et al. [15] showed a biocontrol action of a blend of _T. delbrueckii_ and _Metschnikowia pulcherima_ applied to a machine harvester as compared to the standard addition of SO\({}_{2}\) in the Cabernet Sauvignon variety. In agreement with [PERSON] et al. [19], the addition of _T. delbrueckii_ DiSVA 130 showed a controlling effect over wild yeasts during the first two days of fermentation, although slightly lower if compared with the sulfites fermentation control trial. However, _T. delbrueckii_ DiSVA 130 effectively limited the development of wild yeasts, demonstrating its effectiveness to protect must. Several modalities of actions that can explain the biocontrol action of some strains of _T. delbrueckii_ are still to be evaluated. Some strains of _T. delbrueckii_ were identified to possess the killer character [31; 33; 34]. On the other hand, other antimicrobial actions, such as competition for nutrients or the production of antimicrobial peptides, could be involved. The impact of _T. delbrueckii_ on fermentation and aroma enhancement has been documented over the years [35; 36]. A lot of studies showed the positive contribution of _T. delbrueckii_ strains and their relative positive impact on wine quality [9; 20; 37]. This non-_Saccharomyces_ yeasts is recommended for the fermentation of both dry and high-sugar grapes for the low production of acetic acid. [PERSON] and coworkers [38] already demonstrated that multi-starter fermentation with _T. delbrueckii_ greatly affected the content of several important volatile compounds, including 8-phenyl ethanol, isoamyl acetate, fatty acid esters, C4-C10 fatty acids, and vinyl phenols. [PERSON] and [PERSON] [31] analyzed the variable behavior of _T. delbrueckii_ considering the strain's differences and wine varieties, with a special emphasis on the proposals for industrial use of this species. The production of esters by _T. delbrueckii_ might be strain-dependent and it is further modified in the presence of _S. cerevisiae_ during multiple fermentations [9; 39]. This could explain some of the results obtained in this work concerning the volatile compounds phenyl ethyl acetate and 8-phenyl ethyl ethanol, which typically increase in the presence of _T. delbrueckii_. In the first set of trials, conducted with and without sulfur dioxide, _T. delbrueckii_ DiSVA 130/_S. cerevisiae_ DiSVA 709 trials showed a slight increase in phenyl ethyl acetate only, while isoamyl acetate and phenyl ethyl ethanol increased significantly only without sulfur dioxide. In the second set of the trials, both _T. delbrueckii_ DiSVA 130 and the commercial strain ALPHA(r) in sequential fermentation with _S.