PDF《华东理工大学学位论文》

分类号: 密级: U D C: 华东理工大学学位论文减压精馏方式实现纤维素酶的 生物炼制过程循环利用 雷成 指导教师姓名: 鲍杰 教授 华东理工大学 申请学位级别: 硕士 专业名称: 发酵工程 论文定稿日期: 2015-4-14 论文答辩日期: 学位授予单位: 华东理工大学 学位授予日期: 答辩委员会主席: 评阅人: 作者声明我郑重声明:本人恪守学术道德,崇尚严谨学风.

所呈交的学位论文,是本人在导 师的指导下,独立进行研究工作所取得的结果.除文中明确注明和引用的内容外,本论 文不包含任何他人已经发表或撰写过的内容. 论文为本人亲自撰写, 并对所写内容负责. 论文作者签名: 年月日华东理工大学硕士学位论文 第I页减压精馏方式实现纤维素酶的生物炼制过程循环利用 摘要 纤维素酶成本是阻碍木质纤维素生物炼制技术产业化的重要原因.目前报道的纤维 素酶循环利用方法的适用对象是高酶用量、低固体底物和纯净纤维素底物体系,不具备 实用价值. 本研究通过在位间歇减压精馏方式实现高固含量的玉米芯工业残渣和玉米秸 秆原料乙醇生产中纤维素酶的循环利用,将乙醇分离与纤维素酶循环整合到同步糖化与 发酵工艺中.减压条件下的低温使得发酵醪中大部分的酶活得以保留,补加新鲜底物以 重新吸附纤维素酶后,启动新一轮同步糖化与发酵.循环过程中还监测了纤维素酶系的 相对酶活、pNPG 酶活和 CMC 酶活在循环利用过程的变化.通过 Aspen plus 流程模拟 模型对常规工艺和减压精馏纤维素酶循环工艺的能耗及成本进行了严格计算,发现减压 精馏纤维素酶循环工艺的纤维素酶用量比常规酶用量节省 20-44%,乙醇生产成本降低 了14-27%.在现有高昂的商品纤维素酶成本考虑下,本文提出的纤维素酶循环方法将 具有广阔的运用前景. 本文还对脱木质素玉米芯工业残渣进行乙醇发酵性能测试,在常规固含量及酶用量 下的同步糖化与发酵过程,乙醇浓度达 75.07 g/L,得率为 89.38%,与玉米粉淀粉原料 的发酵技术指标基本一致,具有替代粮食原料的现实竞争力. 关键词:纤维素乙醇;

纤维素酶循环利用;

减压精馏;

同步糖化与发酵;

成本估计 第II 页 华东理工大学硕士学位论文 Cellulase Recycling via Vacuum Distillation During Cellulosic Ethanol Production Abstract High cellulase cost is the main obstacle for commercialization of cellulosic ethanol production. Cellulase recycling is the most efficient method to reduce enzyme cost and ethanol production cost. However, the current reported cellulase recycling methods were related to high enzyme dosage, low solids loading, pure cellulose etc, which were not feasible in practice. In this study, cellulase recycling via vacuum distillation was used during cellulosic ethanol production from delignified corncob residue and pretreated and biodetoxified corn stover. Ethanol was pumped out at lower temperature under vacuum condition, and cellulase activity remained at a high level. Following the first vacuum distillation operation, fresh material was fed into the bioreactor, and the next SSF operation was initiated. This repeated SSF process was conducted for

5 times with the delignified corncob residue and

3 times with the pretreated and biodetoxified corn stover. Meanwhile, enzyme activities against feedstock, pNPG, CMC were measured during the repeated SSF. Energy consumption was calculated through flowsheet simulation model established using Aspen plus software for comparison of ethanol production cost. 20-44% enzyme dosage was saved and 14-27% ethanol production cost was decreased using repeated SSF. Considering the high price of cellulase, recycling via vacuum distillation is a promising strategy. In addition, delignified corncob residue (DCCR) was used as the feedstock of ethanol production by simultaneous saccharification and fermentation (SSF). The ethanol titer and yield reached 75.07 g/L and 89.38%, respectively, using a regular industrial yeast strain at moderate cellulase dosage and high solids loading. The fermentation performance and cost of DCCR and corn meal was compared as feedstock of ethanol fermentation. The result shows that the DCCR is competitive to corn meal as ethanol production feedstock. Keywords: Cellulosic ethanol;