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题名	麦草的常压甘油自催化组分分离及其2,3-丁二醇发酵
作者	孙付保
学位类别	博士
答辩日期	2008-09-15
授予单位	中国科学院过程工程研究所
授予地点	过程工程研究所
导师	陈洪章
关键词	麦草 常压甘油自催化分离 酶解 2 微生物发酵 多粘类芽孢杆菌(B. polymyxa S-07) 3-丁二醇
其他题名	Fractionational separation of wheat straw with atmospheric glycerol autocatalysis and its 2,3-butanediol fermentation
学位专业	生物化工
中文摘要	木质纤维类生物质复杂的化学组成和多级不均一的致密结构，是生物质难以综合利用的根本所在。基于组分分级分离和高值转化的生物量全利用理念，找寻一种简单经济、安全高效和环境友好的新型组分分离方法是实现生物质综合利用的关键。为此，本文通过一系列高沸溶剂的比较分析，选择一种新型预处理溶剂，然后尝试构建了常压高沸溶剂自催化的组分分离策略，最后对该策略预处理的麦草以自主分离菌进行生物基化学品2,3-丁二醇新型发酵的探索。主要实验结果如下： (1) 用于组分分离的高沸点有机溶剂的比较分析：通过比较一些高沸点有机溶剂直接或微波辅助预处理（汽爆）麦草时的预处理选择性和纤维可酶解性，发现高沸点甘油作为预处理溶剂时的预处理选择性最好，原麦草比汽爆麦草更适合作为甘油预处理的生物质原料。最终选择甘油作为木质纤维类生物质原料的预处理溶剂。 (2) 常压甘油自催化组分分离策略的构建： 常压下每克麦草添加15 g工业甘油在240 ℃蒸煮4 h，能使麦草保留95%纤维素，同时脱除90%半纤维素和70%木质素，使预处理麦草湿基48 h酶解率达到90%以上。70%甘油溶液预处理在初始液固比20 g甘油溶液/g干麦草，预处理温度220 ℃和3 h的适宜条件下，能保留麦草中98%纤维素，同时脱除70%半纤维素和65%木质素，使预处理麦草湿基48 h酶解率达到90%。生物柴油和油脂化学工业的粗甘油直接用于该预处理策略时，粗甘油中的脂溶性杂质在预处理过程中发生了‘树脂沉积’现象，尽管树脂沉积物本身对纤维酶解没有明显影响，但它导致‘木质素钝化’而不利于木质素脱出（木质素脱除30%左右）；在粗甘油预处理麦草中，部分残渣木质素通过木质素再缩合和/或形成木质素-碳水化合物复合体(LCC)形式沉淀在纤维上，它们可能随着烘干时纤维角质化的出现而加速形成，木质纤维的这些结构变化将加重它难以水解，致使甘油预处理麦草干基酶解率比湿基低10%以上。粗甘油可用于常压甘油自催化预处理策略，但建议使用前应预先脱除其中的脂溶性化合物。 (3) 常压甘油自催化预处理有效促进木质纤维类生物质原料酶解的机理： 该预处理策略有效提高生物质原料的可酶解性，是由于：脱除了木质纤维中酶解抑制性化学组分，如：乙酰基、半纤维素和木质素等；解剖了生物质原料复杂致密的顽抗性结构，使生物质在器官和细胞水平上相解离；修饰改进了木质纤维中不利于酶解的理化结构，如：使纤维束变得松散、纤维平均尺寸减小、纤维粗糙度和比表面积增加等。 (4) 由常压甘油自催化预处理麦草发酵2,3-丁二醇的探索： 从土壤中分离到1株具有较高木质纤维降解能力的2,3-丁二醇产生菌(Bacillus polymyxa S-07)，经初步优化获得它的培养条件如下：甘油预处理麦草70 g L-1，初始pH 5.5，酵母膏1.5%，培养温度35 ℃和转速120 r/min。该菌株由葡萄糖的2,3-丁二醇转化率为19.4%，由常压甘油自催化预处理麦草作碳源时无需添加纤维素酶，发酵96 h时达到最大纤维素酶活0.946 U ml-1，发酵120 h后能分别降解56.7%纤维素和32.2%半纤维素，生成7.73%2,3-丁二醇（基于底物干重），同时也生成2.86%乙偶姻和1.83%乙醇副产物。该过程通过把纤维水解酶制备、酶解糖化和生物基化学品合成整合在一个系统里，实现了从常压甘油自催化预处理木质纤维到2,3-丁二醇的新型微生物转化。
英文摘要	The complex chemical composition and recalcitrant heterogenic structure of lignocellulosic biomass has frustrated the present effort in comprehensive utilization of biomass. Based on the concept of component fractionation and conversion, to find an economic, efficient and environmentally-friendly pretreatment method is the key of achieving the whole biomass utilization. For this reason, in this thesis, a high-boiling-point organic solvent with good pretreatment selectivity was found, and then a novel separation strategy of atmospheric organosolv autocatalysis was constructed. Finally, a novel 2,3-butanediol fermentation process was explored with Bacillus polymyxa S-07, which integrated hydrolytic enzyme preparation, enzymatic hydrolysis and 2,3-butanediol fermentation in one process or system. Some results were as follow: (1) By comparison of pretreatment selectivity and enzymatic hydrolysis characteristics of wheat straw, it was found that glycerol was the most desirable for the organosolv pretreatment among several high-boiling-point organic solvents. (2) With preliminary optimization, the atmospheric glycerol autocatalytic organosolv pretreatment (AGAOP) of wheat straw was carried out at 240 ◦C for 4 h with industrial glycerol addition of 15 g g-1 dry feedstock, resulting in high cellulose recovery (95%) and removal of hemicellulose (90%) and lignin (> 70%). Meantime, 48 h enzymatic hydrolysis yield of the wet pretreated fiber was high up to 90%. With the initial liquid–solid ratio of 20 g aqueous glycerol / g dry wheat straw and at 220 ◦C for 3 h, the AGAOP enabled wheat straw to remove 70% hemicelluloses and 65% lignin, with 98% cellulose retention. After pretreatment, 48 h enzymatic hydrolysis yield of the wet fiber achieved 90%. When crude glycerol from biodiesel and oleochemical industry was directly used as pretreatment solvent in AGAOP, some contained lipophilic compounds formed ‘pitch deposition’ on the pretreated fiber. The pitch deposition led to ‘lignin passivation’ and was adverse to lignin removal, resulting in low delignification (app. 30%). Meantime, some residual lignin was found to deposit on the pretreated fiber in form of the lignin recondensation and/or lignin–carbohydrate complex (LCC). The deposition was aggravated with fiber hornification occurring when the fiber was drying, which helped to explain why dried pretreated wheat straw had a low enzymatic hydrolysis yield, above 10% lower than that of the wet substrate. The crude glycerol was applicable for AGAOP, but it was advisable to remove lipophilic compounds from crude glycerol before the utilization. (3) It was found that the novel AGAOP strategy effectively improved digestibility of lignocellulose, owing to removing some chemically compositional barriers that inhibited enzymatic hydrolysis, such as acetyl group, hemicelluloses and lignin; disintegrating the complex and recalcitrant structure at organ and cell level; and modifying some physicochemically structural impediments that blocked enzymatic hydrolysis, such as a more loose fibril, a smaller average size, and a more roughness and specific surface area. (4) A 2,3-butanediol producing strain, B. polymyxa S-07, was isolated with good cellulase productivity from natural soil. With a simple optimization, 2,3-butanediol fermentation conditions were as follows: AGAOP wheat straw 70 g L-1, yeast extract 1.5%, initial pH 5.5, culture temperature 35 ◦C, and shaking speed 120 r/min. Under controlled condition, with glucose as the carbon source, 2,3-butanediol conversion rate reached 19.4% by the isolated strain. With the AGAOP wheat straw and no extra cellulase addition, the strain produced 0.946 U ml-1 of the maximum cellulase activity at 96 h. After 120 h fermentation, the strain degraded 56.7% cellulose and 32.2% hemicelluloses, and co-produced 7.73% 2,3-butanediol, 2.86% acetoin and 1.83% ethanol.
语种	中文
公开日期	2013-09-13
页码	181
内容类型	学位论文
源URL	[http://ir.ipe.ac.cn/handle/122111/1117]
专题	过程工程研究所_研究所（批量导入）
推荐引用方式 GB/T 7714	孙付保. 麦草的常压甘油自催化组分分离及其2,3-丁二醇发酵[D]. 过程工程研究所. 中国科学院过程工程研究所. 2008.

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