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Improvement of saccharification and ethanol production from rice straw by NMMO and [BMIM][OAc] pretreatments

Poornejad, Nafiseh, Karimi, Keikhosro, Behzad, Tayebeh
Industrial crops and products 2013 v.41 pp. 408-413
acetates, cellulose, crop production, endo-1,4-beta-glucanase, enzymatic hydrolysis, ethanol production, fermentation, glucose, hydrolysis, rice straw, saccharification, solvents
Rice straw, one of the abundantly available and mainly unused lignocellulosic resources in the world, was successfully pretreated with two cellulose solvents to improve enzymatic hydrolysis and ethanol production. The treatments were conducted with N-methyl morpholine N-oxide (NMMO) and 1-buthyl-3-methylimidazolium acetate ([BMIM][OAc]) at 120°C for 1, 3, and 5h with 5% rice straw loading. Then, the treated and untreated straws were subjected to enzymatic hydrolysis at 45°C for 72h by 20FPU cellulase and 30IU β-glucosidase per each gram of substrate. Hydrolysis results indicated complete conversion of glucan in [BMIM][OAc]-treated straw to glucose and hydrolysis yield of 96% for NMMO-treated samples, while the conversion was only 27.7% for the untreated straw. Ethanol production by simultaneous saccharification and fermentation was carried out at 38°C for 48h. The results showed that ethanol production yield was improved from 35.4% for untreated straw to 93.3% and 79.7% after 5h pretreatment with NMMO and [BMIM][OAc], respectively. The structural analysis reveals that the crystallinity reduction was the main reason of the observed improvements.