*2.4. Preparation of Xylose-Rich Hydrolysates from Wheat Bran and Rice Straw*

Xylose-rich hydrolysates from ground and fine ground rice straw samples were prepared by using phosphoric and sulfuric acids. Ground rice straw (average particle size: 1.42 mm) was treated in a blade grinder for 10 min to obtain the fine ground rice straw (average particle size 0.67 mm). The phosphoric acid treatment of ground and fine ground rice straws was performed according to the method of Jampatesh et al. [35]. Briefly, ground and fine ground rice straw samples were soaked in 2N phosphoric acid for 4 h at room temperature and 220 rpm. The dry matter (DM) content of the reaction mixtures was 10 *w/v*%. (Thus, the obtained reaction mixtures contained 5.9 *w*/*w*% phosphoric acid.) After the soaking, the reaction mixtures were treated in autoclave at 121 ◦C for 30 min and then filtered through a nylon filter with 50 µm pore size to separate the obtained xylose-rich hydrolysates and the remaining solid fractions. The xylose-rich hydrolysates derived from the phosphoric acid treatments of ground and fine ground rice straws are referred to as GRS/P and FGRS/P, respectively. The sulfuric acid pre-treatments of ground and fine ground rice straws were performed in reaction mixtures containing 1.5 *w*/*w*% sulfuric acid and 10 *w*/*w*% DM content. The reaction mixtures were treated in autoclave at 121 ◦C for 30 min. Then the xylose-rich supernatants were separated from the solid fractions by using a nylon filter with 50 µm pore size. The xylose-rich hydrolysates derived from the sulfuric acid treatment of ground and fine ground rice straws are referred to as GRS/S and FGRS/S, respectively. Xylose-rich hydrolysates from wheat bran were prepared following a two-step acidic hydrolysis process detailed in our previous study [17]. Briefly, wheat bran (10 *w*/*w*% DM) was treated in the first step in a 90 ◦C water bath by using 1.16 *w*/*w*% sulfuric acid for 50 min or 1.61 *w*/*w*% sulfuric acid for 47 min, resulting in solid residues referred to as WBI and WBII, respectively. In the second step, WBI and WBII (7.5% *w*/*w* DM) were treated by using 1 *w*/*w*% sulfuric acid solution in an autoclave for 30 min at 121 ◦C in order to obtain xylose-rich hydrolysates referred to as WB1/S and WB2/S, respectively. WB1/S and WB2/S were separated from the solid residues by using a nylon filter with 50 µm pore

size. The conditions of the acidic hydrolyses of ground and fine ground rice straws and wheat bran are summarized in Table 1. Xylose-rich hydrolysates of GRS/S and WB1/S were used for xylitol fermentation experiments.


**Table 1.** Different pre-treatment methods of rice straw and wheat bran for xylose-rich hydrolysates.
