纖維素水解酵素作用對於前處理後木質纖維生質物表面形態的影響

Abstract

第二代生質酒精，主要是將木質纖維生質物等富含葡聚糖的生質物，經過前處理後轉換而得。酵素糖化水解時的使用成本佔了生質酒精成本中的大部分，如何有效的利用酵素，需了解酵素與前處理後生質物的交互作用。 在本研究中三種前處理後生質物：稻草酸蒸爆紙漿（SEP）、硫酸鹽未漂白紙漿（UEK）以及硫酸鹽漂白紙漿（BEK）分別以複合酵素C-Tec（Endoglucanase、Exoglucanase、β-Glucosidase以及Xylanase）及單一酵素FiberCare R（Endoglucanase）進行2 hr、24 hr以及48 hr的水解，並以原子力顯微鏡分析纖維表面性質及粗糙度的改變。生質物在經過C-Tec長時間水解後BEK、UEK以及SEP的表面粗糙度會隨著水解時間增加而明顯的下降。在UEK以及SEP的表面可以發現木質素以鐘狀的方式沉積或是殘留，這些木質素在經過C-Tec水解後會隨著半纖維素一同剝離。而在FiberCare R的結果中，除了BEK與C-Tec的結果有相同趨勢外，在UEK在經過水解後表面粗糙度有上升的趨勢，推測是因FiberCare R為單一酵素Endoglucanase，僅能造成纖維素中糖苷鍵結打斷，降低聚合度，較無法造成糖化所致，SEP則無明顯趨勢。經C-Tec處理後的生質物重量損失隨水解時間增加而增加並造成纖維表面水解，降低粗糙度。纖維素的聚合度則在經過24 hr水解後下降最多，FiberCare R水解結果中，重量損失沒有明顯的下降，但在纖維素聚合度則有明顯的下降，此顯示了FiberCare R會有效的降解纖維素中的糖苷鍵結，但無法大量的降解出單糖溶於溶液中，造成重量損失沒有明顯的下降。 此結果顯示不同酵素配比會造成於生質物的不同程度降解，未來期望透過不同的酵素添加方式或是順序，能提高酵素的效率，以降低最終生質酒精生產的成本。

The second generation bioethanol was converted by pretreated lignocellulosic biomass rich in glucan. Enzyme costs during saccharification contain of a significant portion of overall bioethanol production. Understanding interaction between enzyme and pretreated biomass could further facilitate more in-depth utilization of enzyme during saccharification. In this study, atomic force microscopy (AFM) was employed to investigate pretreated biomass surface morphology change during enzyme hydrolysis. Steam-exploded straw pulp (SEP), unbleached kraft pulp (UEK), and bleached kraft pulp (BEK) were used as pretreated biomass, and formulated cellulase and single-component endoglucanase were employed. The results show that surface morphology of pretreated biomass was significantly changed for 2 hr, 24 hr, and 48 hr hydrolysis. Relative roughness values of pretreated biomass hydrolyzed by C-Tec were decreased, and their surface became more smooth and uniformed. On the other hand, the roughness and morphology of pretreated biomass hydrolyzed by FiberCare R had increased or remain unchanged. The changes of the roughness and morphology of pretreated biomass were well correlated with weight loss with respect to degradation of their constituents.