# Radiation-Induced Structural Changes of _Miscanthus_ Biomass
## 3 Results and Discussion
### Effect of Irradiation Treatment on Enzymatic Hydrolysis of Miscantthus  
Table 2 shows the changes in particle size, distribution, and special surface area of _Miscantthus_ biomass after irradiation treatment. As shown in Table 2, the Sauter mean diameter D [3; 2] and the volume average particle diameter D [4; 3] greatly decreased with the increase in absorbed doses.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Absorbed Dose (kGy)** & **0 (Untreated)** & **400** & **600** & **800** & **1000** & **1200** \\ \hline Cellulose (\%) & 36.60 & 37.20 & 33.90 & 33.10 & 31.00 & 23.00 \\ Hemicellulose (\%) & 31.80 & 17.80 & 11.60 & 10.50 & 7.40 & 4.90 \\ Lignin (\%) & 21.30 & 23.10 & 21.70 & 22.00 & 23.00 & 19.70 \\ Total (\%) & 89.70 & 78.10 & 67.20 & 65.60 & 61.40 & 47.60 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Effect of different absorbed doses on the components of _Miscantthus_.  
For the untreated sample, the values of D [3; 2] and D [4; 3] were 23.808 and 221.005 \(\upmu\)m, respectively, higher than those of irradiated samples. For instance, after irradiation treatment at 1200 kGy, the values of D [3; 2] and D [4; 3] were 7.357 and 20.099 \(\upmu\)m, respectively. In addition, the values of d (0.1), d (0.5), and d (0.9) for untreated samples were 18.026, 153.465, and 547.317 \(\upmu\)m, respectively, whereas for the irradiated samples at 1200 kGy, these values significantly reduced to 2.772, 18.423, and 39.082 \(\upmu\)m, respectively. Therefore, an absorbed dose-dependent particle size for irradiated biomass was observed in this work. In detail, with the increase in absorbed doses, particle size distribution moved toward small particles. This showed that the irradiation treatment can remarkably affect both the particle sizes and their distribution due to the destruction of the stubborn structure caused by irradiation. As shown in Table 2, the SSA of the untreated _Miscanthus_ was 0.252 m\({}^{2}\) g\({}^{-1}\), whereas for irradiated samples, SSA showed an absorbed dose-dependent increase and the maximum value was 0.815 m\({}^{2}\) g\({}^{-1}\) at 1200 kGy. These results are in good agreement with our previous works [19; 21]. We demonstrated that the increase in SSA enhances the accessibility of enzymes to cellulose substrate, resulting in the improvement of cellulose digestibility.  
To further confirm the above-mentioned hypothesis, the irradiated biomass underwent enzymatic hydrolysis to reduce sugar production, and the results are shown in Figure 1. In comparison with the untreated _Miscanthus_ sample, the irradiated sample at over 600 kGy had a higher level of methylene blue adsorption (596.99 \(\upmu\)g/g) and a higher reduced sugar yield (557.58 mg/g). The methylene blue adsorption, a factor of enzyme accessibility to the substrate, slowly increased from 555.18 to 596.99 \(\upmu\)g/g in the tested absorbed doses. It increased sugar reduction from 118.27 to 557.58 mg/g. A reasonable explanation is that the accessibility of enzymes increased after the biomass was treated by irradiation, indicating irradiation pretreatment is an effective method to improve the efficiency of enzymatic hydrolysis of a biomass. This phenomenon is in good agreement with that reported by [PERSON] et al. [22], who demonstrated that SSA improvement of sulfite pulp increases the efficiency of enzymatic hydrolysis.