## 3 Results and Discussion
### Fungal Colonization of Solid Substrates and Impact on Their Chemical Composition
ANOVA was conducted on four homogeneous blocks represented by each substrate to verify the significance of the differences between each parameter's values in the cultures and the incubation controls in both the amended and non-amended cultures. Regarding the changes induced by the fungus on the cell wall polysaccharide contents, the percentage removal values of the hemicelluloses were significantly higher than those of cellulose, with the only exception being represented by cultures grown on WB-amended RTB; under these conditions, cellulose removal significantly increased compared to homologous non-amended cultures (23.5 vs. 12.7%). The percentage of hemicellulose removal varied widely, ranging from 12% in cultures grown on SCG to 59.7% in non-amended DSF ones. WB's general effect in amended cultures was to determine an increase in wall polysaccharides' removal levels compared to those observed in non-amended ones. RTB and DSF were exceptions to this rule, since non-amended cultures outperformed amended ones in hemicellulose removals (34 vs. 26.7% and 59.7 vs. 47.6%, respectively). The presence of WB generally improved the cellulose removal in the amended cultures, even though, in some cases, the extents of these increases were slight. In general, this study observed a higher susceptibility of hemicelluloses to degradation than cellulose, regardless of the substrate and presence or absence of WB. These results are in line with several studies which ascribe the higher recalcitrance of cellulose to biodegradation rather than hemicellulose, due to its partial crystallinity [14; 52]. The increase in reducing sugars observed on solid-state cultures on RTB and SCG, compared to the respective incubation controls, testifies to the partial degradation of the structural polysaccharides, although the concentrations of reducing sugars are the result of the balance between the hydrolysis of the polymers themselves and fungal uptake of the monosaccharides made available by the hydrolysis itself. In these cultures, comparing the yield in reducing sugars released by the hydrolysis of cellulose and hemicelluloses and those found in the extracts, it is evident that _A. olivimuriae_ metabolized a high fraction of these (data not shown). Table 3 shows that, with few exceptions, the Klason lignin contents in the cultures did not differ significantly from their respective incubation controls, apparently suggesting that _A. olivimuriae_ does not have ligninolytic aptitudes, as was widely thought for several years for most _Aspergillus_ species [53]. Some studies, conducted in solid-state fermentation and simultaneous saccharification and fermentation with other organisms, suggest that the preferential degradation of cellulose and hemicellulose inevitably leads to a shift in the relative percentage proportions of the wall macromolecules, thus leading to a lignin-enriched residue [20; 54]. For this reason, some studies have proposed normalizing the lignin mass fractions to their respective ash contents [20; 23]. However, even after this normalization, no significant lignin removal was evident in _A. olivimuriae_ solid-state cultures. In this respect, this species differs from other Aspergilli, such as _A. oryzae_[8] and _A. flavus_[55], which have shown ligninolytic potential. Except for the non-amended cultures grown on DSF and barley straw, total phenol concentrations were significantly higher than those of the respective incubation controls. To explain these results, we could hypothesize the hydrolysis of glucosides by \(\beta\)-glucosidase, leading to the release of phenolic aglycones. Alternatively, we might invoke a partial lignin fragmentation, not translating into a substantial decrease in this parameter but leading to the liberation of phenolic hydroxyls or the release of hydroxycinamic acids from WB in amended cultures due to the action of _A. olivimuriae_ feruloyl esterase. Crude lipids were minor components in RTB, barley straw, and DSF, reaching values in the incubation controls lower or slightly higher than 20 g kg\({}^{-1}\).