## 1 Introduction  
In winemaking, the use of selected cultures is a suitable strategy to control the fermentation process and improve organoleptic profiles and specific aroma compounds for the production of distinctive wines [1, 2]. In this regard, the use of selected non-_Saccharomyces_ yeasts under suitable conditions has widened the opportunities for enhancing the specific contribution of yeasts in winemaking. Indeed, their use in mixed and sequential fermentations with the starter _Saccharomyces cerevisiae_ led to an enhancement in the organoleptic qualities of wines and the complexity of aromatic notes [3, 4, 5]. During the last few decades, many studies have focused on the use of non-_Saccharomyces_ yeasts during alcoholic fermentation for variations in several specific wine features such as an increase in glycerol [6], reduction in volatile acidity [7], enhancement in total acidity, and production of polysaccharides [8], while others focused on the enhancement in flavor and aroma complexity [9, 10, 11] or ethanol reduction [12]. In addition to these features, the use of non-_Saccharomyces_ yeasts has been proposed for biocontrol in winemaking. During the last few years there has been a trend in modern oncology to decrease sulfites because of their effect on human health. Although the World Health Organization has a recommended daily allowance (RDA) of SO\({}_{2}\) of 0.7 mg SO\({}_{2}\)/kg of body weight, European law has set the maximum concentrations allowed at 150 mg/L and 200 mg/L in red and white wines, respectively (EU regulation no. 606/2009). Moreover, environmental concerns have led consumers to prefer \"healthy\" products and choose wines with lower levels of sulfites. From this perspective, the attention of winemakers was focused on research based on new strategies to reduce the use of SO\({}_{2}\)which is a chemical additive with a broad spectrum and widely used in the winemaking process [13]. In this regard, in addition to chemical and physical strategies, the use of non-_Saccharomyces_ yeasts could be a suitable and innovative strategy to achieve this goal along with an improvement of the aroma profile of wine. Several studies have reported the bioprotectant activity of non-_Saccharomyces_ yeasts, which were found to be effective against spoilage wild microorganisms [14; 15; 16; 17; 18]. In particular, the presence of the _T. delbrueckii_ strain in grape juice led to a decrease in wild yeast biodiversity if compared to the addition of sulfites [19].  
Among the different non-_Saccharomyces_ wine yeasts used in mixed fermentation with _S. cerevisiae_ in winemaking, _T. delbrueckii_ shows several features that positively affect the wine quality [20] and others that concern microbial interactions, such as the production of active compounds (killer toxin and hydroxytyrosol). Effectively, with respect to the attributes required to perform industrial alcoholic fermentation, among the non-_Saccharomyces_ yeasts, _T. delbrueckii_ is the closest species to _S. cerevisiae_. This affinity could probably be the main reason why _T. delbrueckii_ was the first non-_Saccharomyces_ yeast suggested for winemaking use at an industrial level.  
Based on the aforementioned reasons, a selected strain of _T. delbrueckii_ was used in sequential fermentation with a native _S. cerevisiae_ strain already selected [21] and tested [22] for low-sulfite wine production. The aim was to evaluate the biocontrol and aroma-enhancing features of _T. delbrueckii_ in organic wines using the low sulfite producer _S. cerevisiae_.