## 3 Results and Discussion
### Characterization of the Raw Hydrolysates  
#### 3.2.1 Sugar Composition and Hydrolysis Efficiency  
The sugar composition of the raw hydrolyses obtained by the dilute acid hydrolysis of the lignocellulosic materials is shown in Figure 3. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Composition** & **Banana Peels** & **BSG** & **Corncobs** & **Grape** & **Grape Stalks** & **Sawdust** \\ \hline Moisture (\%) & 89.7 \(\pm\) 0.4 & 72.1 \(\pm\) 0.8 & 8.9 \(\pm\) 0.9 & 58.9 \(\pm\) 0.6 & 9.7 \(\pm\) 0.4 & 9.1 \(\pm\) 0.5 \\ Ash content (\%) a  & 13.4 \(\pm\) 1.7 & 1.3 \(\pm\) 0.5 & 4.1 \(\pm\) 0.5 & 8.7 \(\pm\) 0.8 & 5.4 \(\pm\) 0.7 & 0.5 \(\pm\) 1.1 \\ Cellulose (\%) a  & 21.1 \(\pm\) 1.3 & 19.0 \(\pm\) 1.7 & 28.4 \(\pm\) 0.5 & 12.2 \(\pm\) 0.4 & 17.6 \(\pm\) 2.2 & 42.8 \(\pm\) 1.1 \\ Hemicellulose (\%) a  & 7.3 \(\pm\) 0.5 & 17.6 \(\pm\) 1.2 & 34.1 \(\pm\) 1.2 & 7.3 \(\pm\) 0.4 & 7.8 \(\pm\) 1.0 & 18.0 \(\pm\) 0.6 \\ Xylans (\%) a  & 4.8 \(\pm\) 0.4 & 10.7 \(\pm\) 1.0 & 30.2 \(\pm\) 0.9 & 5.9 \(\pm\) 0.4 & 3.9 \(\pm\) 0.5 & 17.5 \(\pm\) 0.6 \\ Arabimans (\%) a  & 2.5 \(\pm\) 0.3 & 6.9 \(\pm\) 0.7 & 3.9 \(\pm\) 0.8 & 1.4 \(\pm\) 0.2 & 3.9 \(\pm\) 0.9 & 0.5 \(\pm\) 0.1 \\ Total lignin (\%) a  & 14.1 \(\pm\) 0.5 & 16.3 \(\pm\) 0.6 & 17.1 \(\pm\) 2.4 & 18.1 \(\pm\) 0.7 & 18.6 \(\pm\) 0.9 & 17.9 \(\pm\) 0.5 \\ ASL (\%) a  & 6.8 \(\pm\) 0.5 & 11.3 \(\pm\) 0.2 & 6.3 \(\pm\) 2.3 & 3.9 \(\pm\) 0.7 & 7.1 \(\pm\) 1.3 & 9.6 \(\pm\) 0.6 \\ AIL (\%) a  & 7.3 \(\pm\) 0.1 & 5.0 \(\pm\) 0.2 & 10.8 \(\pm\) 2.4 & 14.2 \(\pm\) 0.2 & 11.5 \(\pm\) 0.8 & 8.3 \(\pm\) 0.7 \\ Protein (\%) a  & 6.6 \(\pm\) 0.3 & 27.5 \(\pm\) 0.5 & 3.4 \(\pm\) 0.4 & 9.8 \(\pm\) 0.6 & 9.2 \(\pm\) 0.2 & 0.5 \(\pm\) 0.1 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Composition of the lignocellulosic materials (ASL, acid soluble lignin and AIL, acid insoluble lignin). Figure 3: Sugars concentrations (\(\blacksquare\)) and hydrolysis efficiencies (**O**) of the different raw materials: (**A**) banana peels, (**B**) brewer’s spent grain (BSG), (**C**) corncobs, (**D**) grape pomace, (**E**) grape stalks, and (**F**) sawdust. GluR, XylIR, and AraR represents the percentage of cellulose, xylan, and arabian converted into glucose, xylose, and arabin, respectively. Figure 2: Particle size distribution of brewer’s spent grain (BSG), grape pomace, grape stalks, and sawdust. The highest total monosaccharides concentration was found for BSG hydrolysate (21.5 g/L) with similar contents of glucose and arabin (6.4 \(\pm\) 2.3 and 6.2 \(\pm\) 2.1 g/L, respectively) and slightly higher xylose content (8.9 \(\pm\) 2.6 g/L) (Figure 3B). On the other hand, only 5.66 g/L monosaccharides were attained from grape pomace, with low concentrations of glucose, xylose, and arabin (1.7 \(\pm\) 0.5, 3.1 \(\pm\) 1.3, and 0.9 \(\pm\) 0.3 g/L, respectively) (Figure 3D). Higher glucose concentrations were achieved from banana peels and grape stalks (8.2 \(\pm\) 0.6 and 8.0 \(\pm\) 0.7 g/L, respectively) (Figure 3A,E), while corncobs and sawdust hydrolysates contained the highest concentrations of xylose (8.2 \(\pm\) 1.5 and 10.8 \(\pm\) 1.9 g/L, respectively), which is consistent with the high content of xylans present in these raw materials (Table 2). Moreover, apart from BSG hydrolysate, all the hydrolysates had low contents in arabin (0.4-1.9 g/L) (Figure 3). Compared with the literature, the xylose concentration obtained in the different raw hydrolysates was lower than the reported values. For example, [PERSON] and coworkers [PERSON] and [PERSON] (2018) reported that 7.2 g/L of xylose was obtained by hydrolysis of grape pomace under similar hydrolysis conditions but with a higher hydrolysis time (125 min). Furthermore, corncob hydrolysate's content in xylose (8.2 \(\pm\) 1.5 g/L) was considerably lower than the values reported in several studies (21.7-31.2 g/L) ([PERSON] et al., 2017; [PERSON] et al., 2018; [PERSON] et al., 2018), which is probably related to the fact that no mill treatment was applied to corncobs due to their hard structure.