| Cellulose biomass, the widely distributed inexpensive renewable resource, can be used for production of the large volumes of bio-ethanol. The use of the bio-ethanol will not only reduce the consumption of fossil fuel, but also reduce the harmful component from the automobile exhaust. Then the use of large quantity straw cellulose biomass for bio-ethanol production will greatly reduce the release of greenhouse gases by avoiding directly burning the straw in the farmland, In this dissertation, the pretreatment technique for rice straw with chemical, ILs and hydroxyl radical approaches were studied, meanwhile the simultaneous saccharification and fermentation technique for pretreated rice straw at high dry matter content and fermentation technique for rice straw hemicellulose hydrolysate were also investigated. This research has theoretical and practical significance in both the energy crisis and the environmental pollution.Rice straw was pretreated with acid, lime and sodium hydroxide, respectively. It was found that pretreatment with 2%NaOH at 121℃for 1 h can remove 88.9%lignin and 38.7% hemicellulose. The residues could be degraded by cellulase complex to a rate of 96.1%. The alkaline liquor separated from the reaction mixture could be recycled for 2-3 times in repeated pretreatment batches.The kinetics of cellulase hydrolysis of NaOH-pretreated rice straw and its mechanism were thoroughly investigated, meanwile, the hydrolysis conditions were optimized. It was found that lignin removal play a big role in enhancing enzymatic digestibility of rice straw. The composition of cellulase complex has an important influence on the enzymatic hydrolysis of rice straw. Supplementing cellobiase greatly reduced the feedback inhibition caused by cellobiose due to lack of cellobiase in the cellulase complex. The optimal condition for enzymatic hydrolysis of rice straw was substrate concentration 80 g/L, cellulase 20 FPU/g substrate, cellobiase 12 CBIU/g substrate. The hydrolysis yield under such condition was 86.7%at 48 h in lab scale and 89.3%at 48 h in a 3 L reactor.Based on the sugar producing rate combined with the change of crystallinity indexes of untreated and treated rice straw assayed by infrared method, the IL 1-ethyl-3-methylimid-azolium acetate ([Emim]OAc) was selected from five ionic liquid candidates for pretreating rice straw. Rice straw has a good solubility in [Emim]Oac, which mainly due to the structure transformation of cellulose I into amorphous or cellulose II. The regenerated rice straw properties showed that it was easier to form an enzyme-substrate complex. The combination of enzyme with substrate was so close which could play a role of protective cellulose on resistant to higher temperature, and then could enhance enzymatic hydrolysis. [EMIM]OAc was also found to be toxic on cellulase, and there were almost no sugar in the hydrolysate at 3 M [EMIM]OAc. Meanwhile the results showed that enzymatic hydrolysis of rice straw had some correspondence between lignin removal and crystallinity of cellulose in a certain degree. The removal of lignin and the cellulose crystallinity showed a fitted linear relationship. The chemical structure and crystalline form of rice straw before and after dissolution analysed by FTIR, XRD and SEM showed that the crystalline form of rice straw was partly transformed from cellulose I to cellulose II after [Emim]OAc pretreatment.After rice straw was treated with Ox-B, and the Ox-B concentration, temperature and liquid to solid ratio were optimized, respectively. According to the Box-Benhnken central composite design principles and the experimental design and data fitting by using Design-Expert 7.0 software, the optimal results were the Ox-B concentration 21 g/L, treating temperature 57.2℃, liquid to solid ratio 40:1. The reducing sugar yield was 94.5%by Model Validation Experiments, close to the predicted value. The results showed no significant difference between Experimental result and predicted result. The effect with Ox-B treatment rice straw was pronounced, however rice straw weight loss is relatively large.The cellulose and lignin content were attained to 88.5%and 4.5%respectively when rice straw pretreated by a sequence of dilute acid and dilute alkali. Ethanol concentration of 58.7g/L in fermentation broth was obtained by SSF at substrate concentration 160g/L which were gotten from rice straw pretreated by a sequence of dilute acid and dilute alkali. The requirement for ethanol concentration above 50.0 g/L in the fermentation mixture was fitted, which reducing the energy consumption in cellulosic ethanol distillation. By matter equilibrium SSF of rice straw pretreated by a sequence of dilute acid and dilute alkali by commercial ethanol instant active dry yeast (S. cerevisiae), combined with 0.05 kg of ethanol from the fermentation of hemicellulose hydrolysates, we were able to achieve 0.175 kg ethanol/kg untreated rice straw.Candida shehatae CICC 1766 was used for xylose fermentation. In a defined xylose and xylose/glucose medium, the results showed that the glucose was consumed prior to xylose for cell growth during early stages of the defined xylose/glucose mixture fermentation. The final ethanol concentration, yield and productivity were almost same 16g/L in the xylose medium and glucose/xylose medium at 72h of the fermentation. Fermentation of rice straw hemicellulose hydrolysate showed that Candida shehatae CICC 1766 had good fermentability at lower pH. We found C. shehatae CICC 1766 could directly ferment acid hemicellulose hydrolysate without detoxification and ethanol concentration was 13.7 g/L at 72 h.
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