**Acknowledgements**

the mineral were removed from lignocelluloses by alkali-pretreatment and the additional nutrients were not added in the SSF process (Alfenore *et al*., 2003). Moreover, the fermenta‐ tion process was affected by the inhibitory materials derived from the alkali-pretreatment since *T*SA of both non-pretreated and the alkali-pretreated lignocelluloses were almost same

In the cases of rice straw, silvergrass, and bamboo with relatively high lignin-contents (18.2– 26.2 wt%), the lignin-removal was effective for both saccharification and SSF processes be‐ cause of the larger *E*SA (1.57–3.39) and *E*SSF values (1.45–2.28). However, in the case of napier‐ grass with low lignin-content (14.9 wt%), the *E*SSF value was small (1.18). Figure 4 shows the plots of the *E*SSF values against the lignin-contents of lignocelluloses. As the lignin-contents increased, the *E*SSF values gradually increased. From the extrapolation of a fitting line of the plots, it is assumed that the *E*SSF values at 13.4 wt% of lignin-content will reach 1.0 which means no enhancement effect of lignin-removal. Thus, it was elucidated that the alkali-treat‐ ment was effective for lignocelluloses with higher lignin content than 13.4 wt%, but was not effective as the pretreatment of lignocelluloses with lower lignin content than 13.4 wt%.

**3.5. Availability of napiergrass as raw materials for ethanol production**

100 Sustainable Degradation of Lignocellulosic Biomass - Techniques, Applications and Commercialization

1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4

bamboo (D). The plots showed that the *E*SSF value became 1.0 at 13.4 wt% of lignin content.

*ESSF*

> 12 14 16 18 20 22 24 26 28 Lignin content/wt%

**Figure 4.** Dependence of *E*SSF on the lignin contents in the SSF of napiergrass (A), rice straw (B), silvergrass (C), and

In general, the alkali-pretreatment increases the accessibility of enzymes to the cellulose by the lignin-removal. Therefore alkali-pretreatment is effective for saccarification of the ligno‐ cellulose with higher lignin contents. In the case of napiegrass with low lignin- content,

C

D

A

B

13.4 wt%

(Alvira, 2010).

**4. Conclusion**

This study was done as a part of the project entitled "Research and Development of Catalyt‐ ic Process for Efficient Conversion of Cellulosic Biomass into Biofuels and Chemicals" through Special Funds for Education and Research from the Ministry of Education, Culture, Sports, Science, and Technology of Japan.
