## 2 Results and Discussion
### VOCs Profile Differentiation in Four Growth Media in the Exponential and Stationary Phase
Furthermore, when considered separately as independent variables, medium (PERMANOVA, R = 0.5457, F = 14.415, \(P\) < 0.001) and phase (PERMANOVA, R = 0.0516, F = 2.068, \(P\) = 0.043) were both also statistically supported as volatiles profile differentiation factors. PC1, which discriminates samples from both mDixon treatments, is associated with an increment in dimethyl sulphide, 2-methylpropan-1-ol, isomer1 of methyldecane, isomer5 of methyldecane, and the isomer2 of methylundecane. PC2, which discriminates samples from the OA+PA medium in the lower values, is associated with an increment in the isomer2 of undec-1-ene, the isomer2 of methyldodecane, the isomer2 of trimethyldodecane, the isomer of methylundecanol, and the isomer2 of methylridecane. PC3, which discriminates samples from PA medium in the lower values, is associated with an increment in 2-methyltetrahydrodofuran, hexan-1-ol, pentyl acetate, and undec-5-ene and a decrease in carbon dioxide. Half of the aforementioned compounds (9) also stood out in the UVA (Table S1 and Figure 2), but the PCA allows for the interpretation of the direction of differentiation of each compound according to the loading values on each axis. To the best of our knowledge, many studies have used MVA to evaluate differentiation of the metabolites profiles in bacteria and fungi to discriminate species, even for chemotaxonomic purposes [59; 60; 61; 62], but this is the first report where MVA analysis demonstrates fungi chemical differentiation in the VOCs profiles that is caused by changes in both medium or/and phase of growth. There are some examples where the effect of one of these variables on the volatiles profile has been tested in bacteria [63; 64; 65]; however, the studies in fungi are less frequent [66]. A third multivariate supervised approximation was performed using Projection to Latent Structures Discriminant Analysis (PLS-DA, Figure 5a). The quality of the model was evaluated by the R2X, R2Y, and Q2 metrics. R2X and R2Y support the goodness of the fit, while Q2 > 0.5 reflects the predictability of the model as significant (R2X = 0.686, R2Y = 0.624, Q2 = 0.505). This analysis proves that the volatiles profiles from mDixon and OA+PA are differentiated, as well as the exponential and stationary phases of these two media. To ensure that a model based on a subset of the data can perform equally well on other subsets, we used cross-validation in seven groups and 1000 permutations. Despite the differences in the number of VOCs found between OA and PA media, as discussed before, Figure 5a shows a considerable overlap of these two media in both growth phases. This evidence  
Figure 4: Three-dimensional Principal Component Analysis (PCA) of the volatiles profiles of _M. furfur_ growing in eight different experimental treatments. The ellipses in this plot are confidence intervals of 95% using a normal distribution. For more details about the data distribution in the three axes, see the three-dimensional animation in Figure S2. suggests that some metabolic changes produced in _M. furfur_ in both restricted dietary conditions could be similar, in comparison with the metabolic performance in OA+PA or mDixon. Our findings using this supervised technique demonstrate that the absence of both unsaturated oleic acid and saturated palmitic acid produces major changes in the fungal VOCs. The same was observed for the VOCs produced by _Saccharomyces cerevisiae_ during the fermentation of different beverages, when linoleic acid is added at different concentrations [67]. The changes observed with _S. cerevisiae_ deeply affect food quality in biotechnological and industrial processes, whereas, for _M. furfur_, these modifications help define the interactions between the yeast and other micro-organisms and the host. Surprisingly, the VOCs profile of the OA+PA medium is different from the sum of the ones obtained by the OA and PA media individually (Table 1, Figures 4 and 5a).