离子液体应用于纤维素溶解及原位酶解的研究
文献类型：学位论文
| 作者 | 杨方 |
| 学位类别 | 硕士 |
| 答辩日期 | 2010-05 |
| 授予单位 | 中国科学院研究生院 |
| 授予地点 | 北京 |
| 导师 | 咸漠 |
| 关键词 | 离子液体 纤维素 溶解性 原位酶解 氧化铝柱层析 脂肪酸 |
| 学位专业 | 生态学 |
| 中文摘要 | 纤维素是世界上含量最为丰富的自然资源之一，充分利用纤维素资源制备生物基化学品意义重大。目前，离子液体应用于纤维素的研究主要集中在离子液体对纤维素的溶解以及纤维素的两步法酶解等方面，但是两步法酶解过程存在操作步骤繁琐，再生试剂的污染等缺点。为了克服这些问题，进而提高纤维素酶解效率、实现纤维素材料更加有效地利用，本文进行了以下研究工作：首先，采用简单的合成方法制备了磷酸类（[Mmim][DMP]、[Meim][DMP]、[Maim][DMP] 、 [Emim][DEP] 、 [Eeim][DEP] 、 [Eaim][DEP] ） 及 醋 酸 类（[Et3NH][OAc]、[Amim][OAc]、[Bmim][OAc]）等 9 种低粘度离子液体，利用FT-IR，1H-NMR 对合成的离子液体进行结构表征；考察各离子液体在不同温度下对微晶纤维素的溶解能力，结果表明[Mmim][DMP]及[Meim][DMP]在 40-60℃范围内对纤维素具有较佳溶解性能；分别在普通加热和超声加热处理条件下考察微晶纤维素在离子液体体系中原位酶解的效率，超声处理后纤维素转化率普遍得到提高，其中[Mmim][DMP]/水体系中转化率达到 53.18%；接着在超声处理条件下，通过对原位酶解反应中纤维素酶浓度，温度以及离子液体浓度等参数的优化，构建纤维素原位酶解优化体系——[Mmim][DMP](20%)/水两相体系，转化率达到 95.48%，比水相中提高了 1.23 倍。此外，粘度测定，SEM，XRD 以及 FT-IR表征结果表明，离子液体及超声加热处理前后纤维素形貌发生变化，更易与纤维素酶接触反应，从而使酶解效率提高。最后，利用中性氧化铝柱层析对纤维素原位酶解产物进行分离，通过对洗脱流速以及上样量的研究建立了优化分离方法，葡萄糖和离子液体的回收剂组成、率分别达到 90.14%和 93.38%，并通过 1H-NMR，FT-IR 以及离子色谱等表征手段对两者进行结构及成分鉴定；分别以回收葡萄糖和商品葡萄糖作为培养基成分进行大肠杆菌发酵产脂肪酸实验，监测发酵过程中 OD600、pH 值、葡萄糖量的变化情况以及脂肪酸产量，结果表明微晶纤维素原位酶解反应得到的回收葡萄糖与商品葡萄糖的发酵过程没有明显差异，能够达到生物发酵标准。 |
| 英文摘要 | Cellulose is one of the most abundant natural resources in the world. The efficient utilization or transformation of cellulose into biobased chemicals is of great significance. At present, the application of ionic liquids (ILs) in cellulose research generally revolves around dissolving celluloseinILs and subsequential sarccharification of cellulose brought out by ILs pretreatment. However, the two-step process is painstaking and time consuming work and the use of organic regenerating reagents might lead to serious environmental pollutions. In order to overcome these problems and further improve cellulose conversion, intensive studies were made to achieve more efficient utilization of cellulosic materials.Six alkylphosphate ILs ([Mmim][DMP], [Meim][DMP], [Maim][DMP], [Emim][DEP], [Eeim][DEP], [Eaim][DEP]) and three acetate ILs ([Et3NH][OAc], [Amim][OAc], [Bmim][OAc]) were synthesized through simple method and their chemical structures were confirmed by 1H-NMR and FT-IR. The solubility of microcrystalline cellulose was studied in these nine low-viscosity ILs. Among them, [Mmim][DMP] and [Meim][DMP] performed well in dissolving cellulose at the C. temperature range of 40-60° By investigating the conversion of cellulose during in situ enzymatic hydrolysis with and without ultrasonic pretreatment, we found the conversion of cellulose in [Mmim][DMP]/aqueous was the highest (53.18%) under ultrasound condtions. Thus, [Mmim][DMP] giving favorable solubility and biocompatibility was selected to further optimize the enzymatic reaction parameters concerning cellulase concentration, temperature and IL concentration. Then, a [Mmim][DMP](20%)/aqueous system for in situ saccharification of cellulose was established and the conversion of cellulose was increased to 95.48% (1.23-fold higher than that of the untreated one). Additionally, SEM, XRD, FT-IR and viscosity analysis were applied to elucidate the possible reasons for the enhancement of enzymatic hydrolysis. The morphological changes caused by the ILs and ultrasound treatment resulted in more cellulose accessibility to cellulase, which enhanced the conversion of cellulose.Finally, neutral alumina column chromatography was used to separate the cellulose hydrolysis products. After comprehensive study of the eluent composition, flow rate and sample loading volume, an optimal system was established and the recovery rate of ILs and glucose could reach 93.38% and 90.14%, respectively. The 1 ILs and saccharides were then characterized byH-NMR, FT-IR and ion chromatography. The regenerated glucose was used as the carbon source for recombinant Escherichia coli fermentation to produce fatty acids. Comparing the fermentation parameters of OD600, pH, residual sugar and fatty acid yields, there was no significant difference between the recovered glucose and commercial glucose, demonstrating that glucose recovered from in situ enzymatic saccharification of microcrystalline cellulose was up to the standard for fermentation. |
| 学科主题 | 生物基化学品 |
| 语种 | 中文 |
| 公开日期 | 2011-08-29 |
| 源URL | [http://ir.qibebt.ac.cn//handle/337004/331]  |
| 专题 | 青岛生物能源与过程研究所_材料生物技术研究中心 |
| 推荐引用方式 GB/T 7714 | 杨方. 离子液体应用于纤维素溶解及原位酶解的研究[D]. 北京. 中国科学院研究生院. 2010. |
入库方式： OAI收割
来源：青岛生物能源与过程研究所
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