## 3 Results and Discussion
### Impact of Fermentation Parameters on Population Dynamics
Indeed, in this study, simple sparging of compressed air at the end of exponential growth was used to stay closer to cell capabilities, although the works cited made use of either constant aerobic conditions [20; 46] or multiple oxygen pulses over the fermentation process [17]. Concerning nitrogen, a higher concentration in the medium seemed to positively affect the N\({}_{\rm max\,Lt}\) (stand. effect 3.131) but with low significance (\(p\)-value 0.052). As previously discussed for \(\mu_{\rm max}\), the chosen nonscarce nitrogen conditions may explain this lack of significant impact on this population variable. The incubation ratio had no significant effect on the maximal population obtained for both yeasts, thereby supporting the work of [PERSON] et al. (2011) [47], who observed the same maximum population (but with longer persistence) of \(Lt\) when favored by the inoculum ratio. As the effects observed on the \(\mu_{\rm max}\) and N\({}_{\rm max}\) were different, the AUC was calculated to assess the impact of fermentation parameters on the population dynamics more precisely (see additional data in Table 11). Yeast distribution over time (AUC\({}_{\rm Lt}\)/AUC\({}_{\rm Sc}\)) was significantly and mainly managed by temperature (var. contribution 40.80%, stand. effect \(-\)8.267), but also by yeast ratio (var. contribution 29.20%, stand. effect \(-\)6.999) and oxygenation (var. contribution 27.80%, stand. effect 6.822), as illustrated in Figure 1.  
A lower fermentation temperature, an inoculation ratio favoring \(Lt\) (lower \(Sc/Lt\) ratio), and air sparging at the end of exponential growth phase all led to a significant increase in the overall presence of \(Lt\) compared to \(Sc\) throughout fermentation (higher AUC\({}_{\rm Lt}\)/AUC\({}_{\rm Sc}\)). The inoculation ratio was quite straightforward, favoring \(Lt\) during the early days of culture, either directly by increasing its relative population at inoculation, or more indirectly by limiting the \(Sc\) population early on and thus reducing its potential negative interactions toward \(Lt\). Oxygenation probably acted as described in the literature, as hypothesized by [PERSON] et al., by allowing the \(Lt\) population to better fulfill its oxygen needs, consequently allowing for better persistence over time and leading to higher cell counts through the stimulation of the respiratory metabolism over the fermentative one [17]. Moreover, [PERSON] et al. (2021) [48] observed the population dynamics during the spontaneous fermentation of natural grape musts and also showed that aeration led to an increased proportion of non-_Saccharomyces_ yeasts in the natural consortium, possibly related to the modification of membrane lipid composition, conferring a higher ethanol tolerance to the yeasts in question. The temperature effect on the AUC ratio probably resulted from previously discussed effects on the \(\mu_{\rm max}\), with quicker \(Sc\) growth inducing a quicker takeover of the culture media. Considering these very important impacts of temperature, ratio, and oxygenation on the population dynamics (especially the AUC ratio), only two conditions (D and G: 18 \({}^{\circ}\)C, ratio \(Sc/Lt\) 0.1, oxygenation) led to the predominance of \(Lt\) on \(Sc\) and to the persistence of \(Lt\) with a high population throughout fermentation (see additional data in Figure 11). The results also showed that the amount of nitrogen in the culture medium had no significant effect on the population dynamics when modulated between the two levels chosen (150 mg\(\cdot\)L\({}^{-1}\) and 300 mg\(\cdot\)L\({}^{-1}\)), except for a small positive but nonsignificant (\(p\)-value = 0.052) effect on the N\({}_{\text{max}}\) for \(Lt\). As discussed for the single variables, the nature of nitrogen sources (ammonium, amino acids, or both) can impact maximal growth and maximal population of \(Lt\) in pure culture, but with strain-dependent variability [21; 35; 49].