臺灣博碩士論文加值系統

木質纖維素(lignocellulose)是最豐沛的可再生生質物，可由農、林廢棄物及能源作物獲得。在經由適當轉化後，木質纖維素可生產生質能源與各式化學品。木質纖維素為複雜之天然高分子複合體其主要由纖維素、半纖維素、木質素所組成，其不同於澱粉質原料可直接經由酵素糖化後發酵，必須透過適當之前處理，適度地破壞其結構，並分離此三種成分，作最有效之運用。由於半纖維素是由五碳糖和六碳糖等成分所構成的多醣，在發酵過程中木糖、半纖維素水解後的主產物，不易被微生物發酵分解，因此在本研究中希望可以將此部分分離出來，進一步轉化生成木寡醣並進行研究探討。
本研究以稻草為原料，先將其經由兩段式的萃取，去除表面的蠟，再藉由微波化輔助鹼處理和酵素水解，探討利用不同溫度和氫氧化鈉濃度和反應時間對木寡醣的影響。結果顯示，前處理溫度與持溫時間的增加，雖然可以提高木寡醣的產率，但溫度變化的影響較小，持溫時間長度的影響較大。隨著NaOH的濃度的增加，木寡醣的產量先增後減。在所探討的三種變因操作範圍中，以在180℃持溫5 min 0.5% NaOH進行鹼處理的樣品所獲得的木寡醣產率為最佳。

關鍵字:稻草、木質纖維素、半纖維素、微波、鹼處理、酵素水解、木寡醣

Lignocellulose is the most abundant renewable biomass, including agricultural and forestry residues and herbaceous and woody crops. Lignocellulosic materials provide a unique resource for sustainable production of bioethanol and chemicals. Lignocellulose is a complicated natural polymer complex, mainly composed of cellulose, hemicelluloses and lignin. Different from starchy materials which can be converted directly through enzymatic saccharification, and fermentation, lignocellulosic materials must go through appropriate pretreatment to disintegrate structure and separate three components moderately to obtain the most effective use.
　　Hemicellulose is a polysaccharide mainly composed of five-carbon and six-carbon sugars. Xylose, the major hydrolytic product of hemicelluloses, is not fermentable to most microorganisms. Therefore, the objective of this study is to separate hemicellulose from lignocellulosic materials and further convert it to xylooligosaccharides.
　　In the study, rice straw was adopted as the raw material. It first went through a two-stage extraction with water and ethanol to remove wax and lignin partly. Secondly, it was subject to microwave-assisted alkali pretreatment to solubilize hemicelluloses. Finally, the soluble hemicellulose was hydrolyzed by enzyme to obtain xylooligosaccharides. Three pretreatment variables, including temperature, sodium hydroxide concentration and reaction time, were investigated to understand their effect to the production of xylooligosaccharides. The results showed that the yield of xylooligosaccharides increased with temperature and reaction time. But the influence of temperature to yield is relatively lower than the influence of reaction time to yield. As the concentration of sodium hydroxide increased, the yield of xylooligosaccharides increased first and then dropped. Among the pretreatment conditions studied, a combination of reaction temperature of 180℃, reaction time of 5 min and sodium hydroxide concentration of 0.5% resulted in a highest xylooligosaccharide yield.

Keywords: rice straw, lignocelluloses, hemicelluloses, microwave, alkali treatment, enzymatic hydrolysis, xylooligosaccharides

目錄

摘要 i
Abstract ii
目錄 iv
圖目錄 vii
表目錄 xi
第一章 緒論 1
1.1前言 1
1.2實驗動機 1
1.3 研究目的 2
第二章 文獻回顧 3
2.1生質物與生質能 3
2.1.1生質能 3
2.1.2 木質纖維素 5
2.1.4 木質素 10
2.1.5 半纖維素 13
2.1.6 木聚醣 14
2.1.6.1 硬木木聚醣 15
2.1.6.2 軟木木聚醣 15
2.2 木質纖維素的前處理 19
2.2.1 機械研磨(Mechanical commimution) 19
2.2.2 熱裂解(Pyrolysis) 20
2.2.3 水熱法 20
2.2.4 稀酸前處理(Diluted acid pretreatment) 21
2.2.5 鹼處理 22
2.2.6 蒸氣爆裂法 23
2.2.7 超音波法 24
2.2.8 微波加熱法(Microwave pretreatment) 25
2.3 木聚醣之水解 26
2.4 半纖維素之應用 28
2.4.1半纖維素多醣 28
2.4.2木糖 28
2.4.3 木糖醇 29
2.4.4 木寡醣 30
2.4.5 木寡醣的制備方法 33
3.1儀器設備與材料 35
3.1.1藥品 35
3.1.2儀器設備 36
3.2實驗方法與步驟 37
3.2.1 稻草可萃取物的去除 37
3.2.2鹼處理 38
3.2.3酵素水解 39
3.2.4稻草成分組成分析 40
3.2.4.1樣品內酸可溶木質素的分析 42
3.2.4.2樣品內酸不可溶木質素及灰份的分析 43
第四章 結果與討論 44
4.1稻草萃取前後之變化 44
4.1.2 掃描式電子顯微鏡分析 46
4.2稻草經鹼處理後消耗率之變化 49
4.3木寡醣濃度與酵素水解時間的關係 53
4.4 鹼處理的NAOH濃度對木寡醣濃度的影響 55
4.6 前處理持溫時間對木寡醣濃度的影響 64
4.7 木寡醣的產量 66
第五章 結論 71
文獻參考 72

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