木聚醣酶與生質物性質對吸附與水解現象之影響

Abstract

第二代生質酒精的原料主要是木質纖維素，其中半纖維素為地表上含量第二豐富的醣類資源，若能善加利用此資源，可使我們的能源供給能更加穩定，進而降低對石化能源的依賴性。 在本研究中，我們利用木聚醣酶、其變異株以及催化區域和鍵結區域對4種不同前處理的基質進行40oC水解和吸附試驗，在試驗過程中，我們透過測定其游離蛋白質含量來確定其已被吸附的程度，再以測定還原糖釋出量來確認酵素的水解效率，在比較酵素及基質吸附水解的結果後，其中含有較多木質素的基質會吸附較多的木聚醣酶且釋出較少的還原糖，使得木聚醣酶的水解效率變低，而含有較少木質素的基質吸附的木聚醣酶量較少，但會釋出比較多的還原糖，因此，酵素水解木質纖維素的效率仍是要視水解出來的還原糖量來確定，而無法純粹以吸附的酵素量多寡來推斷，另一方面，碳水化合物的鍵結區域也是影響水解效率的其中一個因素，具有完整鍵結區域的木聚醣酶還原糖釋出量較多，鍵結區域有缺陷者略差，而不具鍵結區域者幾乎沒有還原糖釋出。 在4oC的吸附試驗中，同樣含有較多木質素的基質具有吸附較多木聚醣酶的能力，但是因此也會影響到親和性的評估，因為其容易產生非專一性的鍵結，不過具有完整鍵結區域的木聚醣酶會有比較強的鍵結力是肯定的。

Second generation biofuels produced from lignocellulosic feedstock materials and the basic structure of all woody biomass consisted of three basic polymers: cellulose, hemicelluloses and lignin. The hemicellulose was the second abundant carbohydrate resource in the earth. If we made good use of it, we could confirm the energy supply and decrease the dependence on petroleum energy. In this study, we used 4 kinds of pretreated substrates to be hydrolyzed and adsorbed by xylanase, its mutants, its catalytic domain and binding domain. Comparing with 40oC adsorption and hydrolysis results, high lignin content substrates adsorbed more xylanase but they released less reducing sugar, which decreased the efficiency of xylanase. Although low lignin content substrates adsorbed less xylanase, they still released reducing sugar more than those containing more lignin. The results showed lignin content had an influence on adsorption and hydrolysis. On the other hand, carbohydrate binding module (CBM) was one of important factors on hydrolysis. With complete CBM, xylanase released more reducing sugar, the one whose CBM had deficiency released less and it would release little reducing sugar without CBM. On 4oC adsorption, high lignin content substrates also had higher maximum adsorption and affected the affinity to enzyme because there was more unspecific binding. The xylanase with complete CBM had higher binding strength with substrates.