## 3 Results and Discussion  
### Characterization of the Raw Materials  
The composition of the lignocellulosic materials (Figure 1) in terms of moisture, ash content, hemicellulose (xylan and arabian), cellulose, lignin (ASL and AIL), and protein is presented in Table 2.  
As shown in Table 2, the materials' moisture content was highly variable, according to their origin and nature. The highest contents were found for banana peels (89.7 \(\pm\) 0.4%), BSG (72.1 \(\pm\) 0.8%), and grape pomace (58.9 \(\pm\) 0.6%). The remaining materials had moisture contents below 10%.  
Figure 1: Photographs of the lignocellulosic materials: (**A**) banana peels, (**B**) brewer’s spent grain (BSG), (**C**) corncobs, (**D**) grape pomace, (**E**) grape stalks, and (**F**) sawdust.  
As expected, lignocellulosic polymers (cellulose, hemicellulose, lignin) represented a large percentage of the total dry weight of the raw materials (Table 2). Corncobs had the highest content of lignocellulosic polymers (79.6%) followed by sawdust (78.7%). BSG, grape stalks, banana peels, and grape pomace exhibited lower contents (52.9%, 44.0%, 42.5%, and 37.6%, respectively). The remaining fraction included other components such proteins, pectin, ash, fats, and oils [21].  
Hemicellulose, the most relevant component for xylitol production, was present at higher contents in corncobs (34.1%), sawdust (18.0%), and BSG (17.6%). On the other hand, banana peels, grape pomace, and grape stalks contained only 7.3-7.8% hemicellulose (Table 2). Cellulose was the major component of lignocellulosic polymers in sawdust (42.8 \(\pm\) 1.1%), but for the other tested raw materials it represented considerably lower of their dry weight (12.2-28.4%) (Table 2). Lignin content was similar for all the raw materials, representing 14.1% to 18.6% of the raw materials' dry weight. These values are in accordance with those reported for the same type of lignocellulosic biomass (Table 2).  
Other components found in the lignocellulosic materials included proteins and ash. Low ash contents (<10%) were found for all lignocellulosic materials, except for banana peels, which had a content of 13.4 \(\pm\) 1.7%. BSG had the highest protein content (27.5 \(\pm\) 0.5%), while the other lignocellulosic materials had considerably lower contents (<10%) (Table 2).  
The particle size distribution of BSG, grape stalks, grape pomace, and sawdust is represented in Figure 2. Corncobs and banana peels were excluded from this analysis due to their physical characteristics, since corncobs were hard to mill and banana peels were too soft, needing to be reduced to purece. As shown in Figure 2, BSG and sawdust were mainly composed of particles smaller than 1.0 mm (90.4 and 85.0 wt%, respectively). Grape stalks, on the other hand, mostly contained particles larger than 2.36 mm (69.8 wt%). In grape pomace, approximately 63.7 wt% of the particles' size was in the range of 1.0-2.36 mm (Figure 2).  
Smaller particle sizes improved hydrolysis efficacy by increasing the surface area to volume ratio. [PERSON] et al. [45] reported dry fractionation of lignocellulosic as an important step and concluded that lignocellulosic materials must have particle sizes between 0.5 and 2 mm to reach a well-accepted level of digestibility. Thus, particle size distribution of BSG, grape pomace, and sawdust are within the values reported, meaning that the effectiveness of dilute acid hydrolysis is increased.