## 4 Conclusions  
Through a multiparametric approach making use of experimental design, this work provided a better understanding of the impact of fermentation parameters on wine fermentation that simultaneously involved _Saccharomyces cerevisiae_ and _Lachancea thermotolerans_. In contrast to most studies, factors here were studied simultaneously and not separately. This global approach allowed us to establish discrepancies between the relative impacts of each parameter studied for the first time. Indeed, previous works mostly focused on one parameter at a time, and not always in controlled and repeatable conditions (natural must, for example). Although these methods had their obvious advantages (better characterization of the single effect of a given factor, closer to real conditions, etc. ), they were often unable to conclude globally by comparing different impacts of factors studied; moreover, the natural media induced variability and hindered reproducibility. The choices made in this study were meant to fill this gap by relying on experimental design as well as the use of a synthetic medium and controlled conditions to help establish how the chosen parameters (inoculum ratio, nitrogen, oxygenation, temperature) could influence fermentation on many interconnected levels (population dynamics, fermentation dynamics and results, final volatile compound profiles). This study suggested that fermentation parameters could constitute tools to control various variables of interest in winemaking, such as the proper implantation of a yeast strain in must, the persistence or dominance of one yeast over another, fermentation time, acidification, and even the characteristics of the final wine volatilome. The population dynamics, as shown, were mostly and strongly impacted by temperature, and to a limited extent by oxygenation. The fermentation dynamics were influenced by temperature and the \(Sc/Lt\) ratio, while lactic acid and pH were dependent on the \(Sc/Lt\) ratio only. The production of volatile compounds (especially alcohols) seemed to be partly modulated by nitrogen content, and this area would therefore be an interesting perspective to explore in further studies. Analyzing precisely how the nitrogen content of the media fluctuates over time during the fermentation process [62] would provide valuable insight by helping to establish links between the modulation of specific compounds and the availability of specific amino acids. Thanks to the global approach taken, this study also highlighted that the production of certain volatile compounds was not only related to the population dynamics, but also was most likely impacted by interactions between species. Further works could eventually go as far as using a sensorial analysis to attempt to link the chosen fermentation parameters and resulting population dynamics to the final wine obtained and its subsequent perception by oenologists and consumers. These results showed that the effects of fermentation parameters were very different depending on which variable was studied, which could explain the variability of the results observed in previous different studies. To manage a mixed culture between \(L\). _thernodelerans_ and \(S\). _cerevisiae_, it is then necessary to follow a global approach (population dynamics, fermentation kinetics and products, physicochemical parameters, aroma compounds, etc.) to find the best compromise between manageable conditions, leading to an optimized wine. For example, the two conditions allowing for the persistence of \(Lt\) until the end were also those that took the most time to complete, and the risk of them becoming sluggish or even stuck was non-negligible. On the other hand, the results showed that the lactic acid content of the final wine could very well be modulated by modifying only the inoculation ratios, without any regard for other factors. Indeed, ensuring adequate \(Lt\) persistence over time did not seem vital to achieving such a goal.