A Novel Combined Pretreatment Method for Rice Straw Using Optimized EMIM[Ac] and Mild NaOH
2016
Raeisi, S Morteza | Tabatabaei, Meisam | Ayati, Bita | Ghafari, Akram | Mood, Sohrab Haghighi
Combined pretreatment methods for improving sugar yield as well as the economic aspects of lignoethanol production processes have gained a great deal of interest. However, most investigations involving such methods have been conducted under optimum conditions. Such fully-optimized combinations although improve enzymatic digestion, they could also degrade cellulose structure resulting in reduced sugar yield in some cases. The present study was set to prepare rice straw for the 1-ethyl-3-methylimidazolium acetate pretreatment step (2 h, 120 °C), by mild alkaline extraction (30 min, 80 °C, 0.3 % NaOH) with a focus on only 30 % lignin removal to minimize the hemicelluloses degradation. Moreover, the effect of size reduction (<0.42 mm and <2 cm) was also investigated. The results showed that the novel combination method based on only 30 % lignin removal led to an increased sugar yield by 17 %. Unexpectedly, although IL pretreatment needs material to be ground (<0.42 mm), the difference in sugar yields for the two sized tested was negligible. The overall lignocellolusic bioethanol production pathway including the combined AE–IL process proposed in the present study based on 30 % lignin removal through the first AE step.
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