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摘要燃料乙醇是以生物物质为原料通过生物发酵等途径获得的可作为燃料用的乙醇。燃料乙醇作为液体燃料和汽油添加剂，是可再生能源，对于缓解能源危机、保护环境具有重要的作用。目前燃料乙醇主要通过玉米发酵获得，但传统工艺没有将玉米中 4%的纤文素转化利用。本研究基于玉米发酵工艺，在其中添加不同纤文素酶，探究了纤文素酶的加量、添加时间和工艺pH 对发酵的影响，并研究了纤文素酶在不同干物浓度下以及添加半纤文素酶对发酵工艺的影响。研究发现添加纤文素酶提高了乙醇产量，其中和氏璧纤文素酶的效果最好；0.6%的纤文素酶添加量对提升乙醇产量最佳；纤文素酶在同步糖化发酵时加入得到的乙醇浓度最高；纤文素酶在 33%的干物浓度工艺比传统的27%干物浓度工艺提升乙醇产量的效果更好。整个发酵过程中,87.22%的乙醇在前 24 小时生成。优化工艺后乙醇浓度达到138g/L，比不加纤文素酶提高 3.4%。 41308
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毕业论文关键词 燃料乙醇 玉米发酵 纤文素酶
Title Study of cellulose conversion during corn ethanol process
Abstract Fuel ethanol is produced from biological materials through fermentation and other means, and is used as a fuel. Fuel ethanol can be used as liquid fuel and gasoline additive, which is renewable energy and plays an important role in alleviating the energy crisis and protecting the environment. At present, the application of corn fermentation technology is widely used in the production of ethanol. However, the cellulose, which accounts for 4% of the corn mass, is not converted in traditional corn ethanol process. This work studied the effect of cellulase addition in corn ethanol process. The factors such as cellulase cocktail source, cellulase dosage, the time for cellulase addition and process pH were examined. We also studied the effect of cellulase addition at different solids loadings as well as the effect of hemicellulase addition. Adding cellulase increased the yield of ethanol and the cellulase cocktail obtained from Heshibi showed the best effect among the tested cellulase cocktails. Cellulase dosage at 0.6% (dry corn basis) enhanced ethanol yield the most. Addition of cellulase during simultaneous saccharification and fermentation was the best process for ethanol enhancement. Addition of cellulase at 33% solids loading increased ethanol yield more than that at 27% solids loading. Kinetic study showed that 87.22% of ethanol was produced during the first 24 h. After optimization, the final ethanol concentration reached as high as 138 g/L, which is 3.4% higher than traditional process without addition of cellulase.
Keywords fuel ethanol corn fermentation cellulase
目次
1引言1
1.1燃料乙醇的研究意义.1
1.2燃料乙醇的国内外发展状况.1
1.3燃料乙醇的生产工艺.2
1.3.1第一代燃料乙醇：玉米燃料乙醇生产工艺.2
1.3.2第二代燃料乙醇.3
1.4纤文素酶.3
1.4.1纤文素酶组成和作用机制.3
1.4.2纤文素酶水解的影响因素.4
1.5本课题的目的.5
2材料与方法6
2.1实验器材.6
2.2实验试剂.6
2.3实验方法.7
2.3.1基本实验步骤.7
2.3.2灭菌条件.7
2.3.3乙醇、木糖、甘油含量测定.7
3实验结果与讨论8
3.1不同厂家的纤文素酶对发酵的影响.8
3.2尤特尔纤文素酶对乙醇产量的影响.9
3.3添加工艺的影响10
3.4不同干物浓度下添加不同量的纤文素酶11
3.5发酵初始pH对发酵的影响.12
3.6纤文素酶与半纤文素酶一同添加的影响13
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