# Aromatic Potential of Diverse Non-Conventional Yeast Species for Winemaking and Brewing
## 3 Results and Discussion
### Comparison Microscale vs.Labscale  
To assess the effect of scaling-up, we compare microscale and labscale fermentations. Specifically, comparison of yeast growth, fermentation performance and aroma profiles were carried out between microwine and wine produced at labscale.  
Similar trends were observed regarding yeast growth and fermentation kinetics despite appearing significant differences in the absolute values, which were expected as a consequence of the differences in oxygen levels, resulting of the differences in volume. The lower the volume, the less anaerobic environment is created. Similar behaviour would happen when scaling-up between lab and pilot scales or between pilot and industrial scales.  
Sugar consumption and ethanol production (Figure 1) were similar up to day 3, and thereafter the microscale was marginally faster, resulting in a full sugar depletion at the end of fermentation. This is in line with the slightly higher biomass in the microwine system (Figure 2) and was according to [31], who observed accelerated sugar consumption in fermentations carried out in MTPs compared to those in Erlenmeyer flasks. However, these authors experienced lower ethanol levels in MTPs at the end of fermentation due to evaporation loss and despite being the same levels at early fermentation stages. In our study, this fact did not occur (Figure 1).  
Most relevant levels of aroma compounds are presented in Figure 3. The significant differences that appeared in practically all the aroma compounds could also be explained by the levels of oxygen present in each scale. It has been demonstrated that differences in aeration causes differences in the  
Figure 1: Fermentation performance in labscale wine and microwine.  
Figure 2: Yeast growth in labscale wine and microwine.  
yield of aroma compounds [32]. The initial oxygenation of the musts causes, in general, higher levels of alcohols and esters [32], which could explain the higher amounts of these aromas found in microscale compared to labscale. This was the case of isobutyl alcohol, isoamyl alcohol, phenylethanol, isoamyl acetate, ethyl caroten and ethyl caprylate. For instance, in the case of higher alcohols, these differences range from 4- to 20-fold [32]. One exception is ethyl acetate, which seems not to be affected by the levels of oxygen according to [32]. In our study, just slightly lower quantities of this compound were found in microscale. Regarding acetaldehyde and diacetyl, the former increased due to the higher presence of oxygen whereas the latter was not affected at all, being the same in both scales.  
So the actual flavour levels in the microsystem were systematically higher than in the lab system. Besides oxygen, this matches with the slightly higher biomass levels and sugar consumption and does not compromise the screening power of the microsystem, although upscaling will always require fine tuning. Our results indicate that microsystems provide a useful and economical platform for the screening of interesting traits in industrial strains, as [31] affirmed, since the results are valid for  
Figure 3: Aroma profiles at microwine and labscale. (**a**) Major compounds; (**b**) Minor compounds.  
comparison purposes. However, scaling-up will always be necessary in order to get closer to real winemaking or brewing processes.