2008-01-012024-05-18https://scholars.lib.ntu.edu.tw/handle/123456789/713142摘要：面臨化石能源枯竭、全球暖化加劇等問題，由木質纖維素（lignocellulose）產製生質酒精為目前發展的趨勢，其中又以利用稻桿、蔗渣等農業廢棄物產製生質酒精最符合經濟效益。以木質纖維素產製生質酒精的過程中，經預處理的原料需進一步利用酵素進行糖化，方能進行酒精發酵。採用之酵素除內葡聚糖&#37238;（endoglucanase）、外葡聚糖&#37238;（exoglucanase）、葡萄&#33527;&#37238;（glucosidase）等纖維素&#37238;以外，亦需有木聚糖&#37238;（xylanase）等半纖維素&#37238;之參與。近年纖維分解酵素之價格雖已降低，但仍為生質酒精生產成本的主要費用。因此，如何提高酵素活性以降低酵素使用成本實有其必要性。此外，改良發酵菌種以提高其對抑制物之耐受性及對五碳糖的利用性雖可進一步降低生產成本，然而發展單一微生物進行酵素生產、酵素水解及酒精發酵等所有反應則可將成本降至最低。本研究即計畫將瘤胃微生物之纖維素&#37238;基因選殖於高效表達系統，並評估重組酵素應用於同步糖化發酵法（simultaneous saccharification and fermentation；SSF）之可行性。亦將瘤胃微生物之纖維素&#37238;基因選殖於啤酒酵母菌，並評估基因重組酵母菌之纖維分解能力及應用於聯合生物加工法（consolidated bioprocessing；CBP）之可行性。<br> Abstract: Bioconversion of lignocellulosic feedstocks to fuelgrade ethanol is a promising route towards reduced dependence on fossil fuels and the mitigation of greenhouse gas production. Feedstocks currently under consideration include agricultural residues, such as rice straw and bagasse. Typical bioconversion schemes involve a pretreatment step to improve substrate accessibility, followed by enzymatic hydrolysis of the cellulose component to produce glucose for fermentation. Efficient hydrolysis of cellulose requires the synergistic activities of three types of cellulase enzymes: endoglucanase, exoglucanase, and β-glucosidase. In addition, hemicellulases such as xylanase that break down xylan are also needed. Although the cost of commercial cellulase preparations has been reduced significantly in recent years, enzyme costs are still an obstacle to full-scale process commercialization. Therefore, it is necessary to improve the enzymatic hydrolysis with efficient enzymes and reduced enzyme production cost. It is also necessary to develop robust fermenting organisms, which are more tolerant to inhibitors and ferment all sugars in the raw material. In addition, one-step conversion of cellulose to ethanol with an organism capable of cellulose degradation and efficient fermentation would greatly enhance cost effectiveness of bioethanol production. In this study, the rumen microbial cellulase gene will be constructed to express in high efficiency expression system. The application of the recombinant enzyme in simultaneous saccharification and fermentation (SSF) of agricultural residues will be evaluated. The rumen microbial cellulase gene will be also cloned and expressed in Saccharomyces cerevisiae. The potential of the recombinant strain to degrade cellulose and be used for consolidated bioprocessing (CBP) will also be evaluated.瘤胃微生物纖維素&#37238同步糖化發酵法聯合生物加工法Rumen microbecellulasesimultaneous saccharification and fermentationconsolidated bioprocessing