# Production of Cellulosic Ethanol from Enzymatically Hydrolysed Wheat Straws
## 3 Results and Discussions
### Determination of Individual Carbohydrates After Enzymatic Hydrolysis  
[PERSON] and [PERSON] (2010) analysed the content of neutral monosaccharides in WS after pretreatment with 0.75% H\({}_{2}\)SO\({}_{4}\) (_v/v_) at 121 \({}^{\circ}\)C for 1 h and hydrolysis (using three commercial enzyme preparations Celluclast 1.5, Novozym 188 and ViscoStar 150 L) obtained the following concentration for glucose--282 mg/g, xylose--180 mg/g and total content of carbohydrates--504 mg/g [71]. [PERSON] et al. (2005) were established from barley straw a concentration of 214 mg/g for glucose, 208 mg/g for xylose+galactose and 452 mg/g for total carbohydrates after pretreatment with 1% (_v/v_) H\({2}\)SO\({}_{4}\) at 121 \({}^{\circ}\)C for 1 h and hydrolysis using the same three commercial enzyme preparations [15]. Analysing different varieties of rice straws, [PERSON] et al. (2011) showed that these contain free fructose with values between 7.4 \(\pm\) 0.1-22.9 \(\pm\) 0.2 g/Kg [72]. Also, [PERSON] et al. (2009) obtained 0.62-2.32% fructose (per dry weight of rice straw (_w/w_)) [73]. In this study, the Box Behnken design based on the response surface methodology with the representation of the experimental values of the independent variables was used to identify the optimal condition in order to obtain the highest carbohydrates content. Figure 3 shows that the highest glucose content was obtained at the correlation of the following parameters--3% H\({}_{2}\)SO\({}_{4}\) (_v/v_), 1/30 ratio and 90/90 \(\mu\)L/g of added enzyme content, and the lowest--1% H\({}_{2}\)SO\({}_{4}\) (_v/v_), 1/20 ratio and 30/30 \(\mu\)L/g of added enzyme content. This tendency is also manifested for the other analysed parameters (fructose content-Figure 4, xylose-Figure 5 and the total carbohydrates content--Figure 6). The equation for glucose content (mg/g sample) is presented in the Equation (2):  
\[ \begin{array}{l}Glucose\ =59.5633+1.7338\cdot X_{1}+24.3427\cdot X_{2}+2.2761 \cdot X_{3}-0.1350\cdot X_{1}\cdot X_{2}\\ +0.1666\cdot X_{1}\cdot X_{3}+0.2800\cdot X_{2}\cdot X_{3}+0.2050\cdot X_{1}^{2 }\\ -2.1916\cdot X_{2}^{2}-0.7816\cdot X_{3}^{2}\end{array}  \tag{2}\]  
where: \(Y_{1}\)--the value of the glucose content parameter, mg/g sample; \(X_{1},\ X_{2},\ X_{3}\)--coded values for sulfuric acid content (%), S/L ratio (_w/v_) and added enzyme content (\(\mu\)L/g sample). Figure 3: 3D diagrams of glucose content. The equation for fructose content (mg/g sample) is presented in the Equation (3):  
\[ \begin{array}{l}\begin{array}{l}\mbox{{\it Fructose }}=4.7733+0.0277\cdot X_{1}+1.7327\cdot X_{2}+0.6527\cdot X_{3}-0.3141\cdot X_{1 }\cdot X_{2}+\\ 8.3\cdot 10^{4}\cdot X_{1}\cdot X_{3}+0.4766\cdot X_{2}\cdot X_{3}+0.1533\cdot X _{1}^{2}-0.1516\cdot X_{2}^{2}-0.4916\cdot X_{3}^{2}\end{array}\end{array}  \tag{3}\]  
where: \(Y_{1}\)--the value of the fructose content parameter, mg/g sample; \(X_{1},~{}X_{2},~{}X_{3}\)--coded values for sulfuric acid content (%), S/L ratio (_w/v_) and added enzyme content (\(\mu\)L/g sample). The equation for xylose content (mg/g sample) is presented in the Equation (4):  
\[ \begin{array}{l}\begin{array}{l}\mbox{{\it Xylose }}=6.3244+2.0000\cdot X_{1}+2.2583\cdot X_{2}+0.2638\cdot X_{3}+0.3458\cdot X _{1}\cdot X_{2}\\ +0.3175\cdot X_{1}\cdot X_{3}+0.1358\cdot X_{2}\cdot X_{3}+1.3333\cdot X_{1}^{2} \\ +0.8450\cdot X_{2}^{2}-0.1116\cdot X_{3}^{2}\end{array}\end{array}  \tag{4}\]  
where: \(Y_{1}\)--the value of the xylose content parameter, mg/g sample; \(X_{1},~{}X_{2},~{}X_{3}\)--coded values for sulfuric acid content (%), S/L ratio (_w/v_) and added enzyme content (\(\mu\)L/g sample). Figure 4: 3D diagrams of fructose content. The equation for carbohydrates content (mg/g sample) is presented in the Equation (5)  
\[ \begin{array}{l}Total\ of\ carbohydrates=70.6592+3.7616\cdot X_{1}+28.3344\cdot X_{2}+3.191 1\cdot X_{3}\\ -0.1016\cdot X_{1}\cdot X_{2}+0.4850\cdot X_{1}\cdot X_{3}+0.8916\cdot X_{2}\cdot X _{3}+1.6905\cdot X_{1}^{2}\\ -1.4977\cdot X_{2}^{2}-1.3844\cdot X_{3}^{2}\end{array}