## 4 Discussion  
In the last two decades, there has been an average increase of two degrees of alcohol in wine due to climate change and the technology used and required by consumer demands. Overall, the combination of health, economic, and quality issues associated with high-alcohol wines has led to significant interest in the development of technologies for producing wines with reduced ethanol concentrations. Several approaches have been proposed to reduce the ethanol content in wine. Among biotechnological approaches, the use of non-_Saccharomyces_ yeasts in different fermentation conditions can lead to the achievement of this goal [8, 15, 18, 19, 23, 43, 44, 45]. A valuable fermentation strategy is the addition of air during the first stages of fermentation to allow the consumption of sugar through yeast respiration [46, 47]. Among non-_Saccharomyces_ yeasts, _S. bombicola_ has been extensively studied in different fermentation conditions and grape varieties to achieve the goal of improving some specific analytical compounds [48, 49]. In this investigation, the use of _S. bombicola_/_S. cerevisiae_ under limited aeration conditions (20 mL/L min) at pilot scale sequential fermentation was evaluated to reduce the ethanol content and increase the aroma complexity in Montepulciano wine production. The use of selected non-_Saccharomyces_ yeasts in sequential fermentation with _S. cerevisiae_ to reduce the ethanol content was well investigated at the laboratory level but is poorly evaluated under winery conditions [43]. In previous studies, this strain of _S. bombicola_ was used in different fermentation conditions to reduce the alcohol content in wine and increase the glycerol content [15, 48, 49]. _S. bombicola_ was used in immobilized form to start fermentation, followed by inoculation of free _S. cerevisiae_ cells. This led to wine with a 1.6% \(v/v\) reduction in the final ethanol content in comparison with _S. cerevisiae_ starter strains [15]. In a subsequent study, _S. bombicola_ bench-top fermentation conducted in Verdicchio grape juice supplemented with 20 mL/L/min of air during the first 72 h produced a wine with an ethanol reduction of 1.46% (\(v/v\)) [30]. Here, under winery conditions, _S. bombicola_/_S. cerevisiae_ red winemaking fermentation, supplemented with air during the first 72 h, resulted in a reduction of ethanol of 0.80% (\(v/v\)). In comparison with the laboratory conditions and immobilized cell inoculum, there was a lower ethanol reduction, even if an 0.80% (\(v/v\)) reduction may be a valuable starting point in winery conditions. The scale-up conditions showed several concerns linked to winery conditions and difficulty in controlling the  
Figure 3: Sensory analysis of wines produced in the pure and mixed fermentations: (**a**) olfactory analysis and (**b**) taste analysis. _S. cerevisiae_ (), _S. bombicola_/_S. cerevisiae_ (). *, Significantly different (Fisher ANOVA; \(p\)-value 0.05). ferentation process with particular reference to mixed fermentations. Also, in this case, a relevant presence of wild yeasts (mainly \(H\). _uvarum_ and \(S\). _bacillaris_) in the sequential trials was found. The presence of grape skins (ferentation with maceration) facilitates the presence of wild yeasts in the must and makes it more difficult for the inoculated \(S\). _bombicola_ strain to dominate the fermentation process. Better control of wild yeasts and an increase in the inoculation level of \(S\). _bombicola_ could enhance the competitivity. Regarding the structure and aromatic profile of wine, this fermentation strategy led to an increase in glycerol content of approximately 4.5 g/L. The ethanol reduction achieved in the present work could be, at least in part, explained by the relevant increase in glycerol, as previously reported by [PERSON] and [PERSON] [50]. A similar result was obtained with _Candida zemplinina_ (synonym _Starmerella bacillaris_, a closely related species with similar oenological features to \(S\).