## 3 Results and Discussion  
### Fermentation Kinetics  
Non-_Saccharomyces_ yeasts in pure or sequential fermentation with _S. cerevisiae_ QA23 were used as an alternative solution to overcome the drawback of a single commercial species process and to improve the complexity, sensory properties, and flavor of wines [10; 12; 23]. Additionally, more attention is paid to non-conventional indigenous yeasts with good enological potential, with the aim to differentiate wine productions and ultimately shape and contribute to the regional wine characteristics [24; 25; 26; 27; 28; 29].  
In our previous studies, we showed that some commercial and native non-_Saccharomyces_ yeasts have a positive impact on the quality, volatile, and sensory profile of Prokupac red wines [14; 19; 21]. Since the results were demonstrated at laboratory level, the logical continuation of the research was validation at the industrial level. The first step was examination of sugar consumption kinetics in pure and sequential fermentations (Figure 1).  
Regardless of the yeast strain or fermentation protocol, a typical fermentation curve was observed for all fermentation trials. In the control sample, fermentation was completed 5 days after inoculation, while for the non-_Saccharomyces_ strains, fermentation lasted for more than 8 days. About half of the sugar amount in grape juice was depleted after 70 h of fermentation by _S. cerevisiae_ QA23, while more than 80% of sugar remained not consumed by _C. famata_ WB-1 and _H. uvarum_ S-2 strains, regardless of the fermentation protocol, even after 90 h of inoculation. Among both used non-_Saccharomyces_ yeasts, faster reduction of sugar content was observed for _H. uvarum_ S-2, independently on the fermentation protocol, indicating slightly better fermentation ability of this strain. Furthermore, after co-inoculation with commercial yeast _S. cerevisiae_ QA23, the fermentation was accelerated compared to the pure fermentations with _C. famata_ WB-1 and _H. uvarum_ S-2. However, both pure fermentations required an additional 24 h for dryness to be attained, compared to the sequential fermentation inoculated with the samenon-_Saccharomyces_ isolates. Additionally, during the monitoring period, all fermentations were performed with no stagnation. Good fermentation ability of _C. famata_ WB-1 and _H. uvarum_ S-2 was consistent with our previously published results for the laboratory fermentation trials [14; 19]. Similar fermentation abilities were earlier reported for _H. uvarum_ strains isolated from spontaneous fermentation of Negroamaro [13] or Montepulciano d'Abruzzo and Trebbiano [30] grapes and for some other non-_Saccharomyces_ yeasts such as _Candida zemplinina_[30], _Lachancea thermotolerans_[31], _Torulaspora delbrueckii, Kluyveromyces thermotolerans_[32], and several species of the genus _Kazachstania_[33]. Such fermentation characteristics indicated that both tested non-_Saccharomyces_ yeasts (_C. famata_ WB-1 and _H. uvarum_ S-2) could be considered as possible starter cultures in industrial-scale vnification, without the risk of stuck or sluggish fermentations. Moreover, the slower alcoholic fermentation observed for tested isolates does not necessarily represent a disadvantage, especially when bearing in mind that slower fermentation rate results in a cooler fermentation, leading to better retention of volatile compounds and lower demand for energy, which prevents overheating during the fermentation [34].