## 3 Results and Discussion
### Phenolic Profile, Sugars and Sugar Degradation Compounds  
The analysis of glucose and xylose in the liquors (Table 4) coming from cellulose and hemicellulose hydrolysis, respectively, seems to confirm the higher severity of the conventional acid hydrolysis, particularly regarding the effect on hemicellulose, since xylose concentration was nearly 100 times that in the auto-hydrolysis liquor, while the glucose concentration was 15 times higher. Even considering the double liquid to solid ratio adopted in the autohydrolysis process, the sugars yield was higher with the acid hydrolysis. Moreover, acetic acid content was higher both in concentration and in overall yield. Acetic acid originates from the removal of acetyl groups of hemicellulose and oxidation of released monosaccharides; therefore, its values agree with those of glucose and xylose. However, HPLC analysis revealed a lower yield of sugar degradation products for conventional acid hydrolysis. This means a higher severity of the auto-hydrolysis from the point of view of sugar degradation. This might indicate both that the auto-hydrolysis is less aggressive than the acid hydrolysis step in causing the degradation of fibers into monomers, and that the high temperatures involved in auto-hydrolysis leads to a higher conversion of released sugars into furans. This might be negative if the liquors are meant to be used as substrate fermentation due to the typical anti-fermentative potential of these compounds, but it could be positive due to the important role of furans as starting molecules for many other compounds [59].  
Acid liquors were also analyzed for the phenolic profile (Table 4), looking for the phenolic acids and aldehydes that typically originate from lignin depolymerization and solubilization [60]. A few phenolic acids were detected, at very low concentration, only in the acid liquor, maybe due to their degradation under the high temperature reached in the auto-hydrolysis. Apart from these compounds, HPLC analysis confirmed the higher antioxidant content and power previously reported for the auto-hydrolysis based on the higher vanillin and syringaldehyde yield. Moreover, the data reported in Table 4 are in agreement with the values obtained from the analysis of [PERSON] et al. [15] and of [PERSON] et al. [61], despite the first being started with a lower liquid to solid inlet ratio (i.e., 1:10 compared to 1:20), while the second operated with milder conditions (i.e., 180 \({}^{\circ}\)C compared to 190 \({}^{\circ}\)C).  
\begin{table}
\begin{tabular}{l c c} \hline \hline
**Parameter** & **Auto-Hydrolysis** & **Acid Hydrolysis** \\ \hline FRAP \(\mu\)molFe/g\({}_{\text{dm}\text{WS}}\) & 309.26 \(\pm\) 32.42 & 67.27 \(\pm\) 2.00 \\ FRAP molFe/molGAE & 2.62 \(\pm\) 0.27 & 2.44 \(\pm\) 0.07 \\ ABTS \(\mu\)molTrolox/g\({}_{\text{dm}\text{WS}}\) & 93.89 \(\pm\) 6.47 & 4.06 \(\pm\) 1.32 \\ ABTS molTrolox/molGAE & 0.80 \(\pm\) 0.05 & 0.15 \(\pm\) 0.05 \\ Superoxide (\%SRSA/mg\({}_{\text{dm}\text{WS}}\)) & 387.15 \(\pm\) 79.94 & 80.49 \(\pm\) 11.91 \\ Superoxide (\%SRSA/\(\mu\)MGAE) & 0.34 \(\pm\) 0.072 & 0.29 \(\pm\) 0.048 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Antioxidant power of wheat straw (WS) auto-hydrolysis and acid hydrolysate liquors measured with different assays (FRAP, ABTS and Superoxide). Values are reported as mean values (\(n=3\)) \(\pm\) sd.