以溼氧蒸煮爆碎前處理法提升稻殼糖化效率的研究

Enhancement of Enzymatic Saccharification of Rice Hulls by Wet Oxidative Steam Explosion Pretreatment

謝伯祥(Bo-Shiang Shie)

指導教授 ： 余琬琴

國立臺北科技大學/工程學院/有機高分子研究所/碩士(2009年)

https://doi.org/10.6841/NTUT.2009.00241

摘要

木質纖維素（lignocellulose）是來源最豐沛的可再生生物質（renewable biomass），可用來生產生質燃料與化學品，但是，木質纖維素是一種複雜的天然高分子複合體，主要由纖維素、半纖維素、木質素組成，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，方能作最有效之運用。
本研究以稻殼為原料，利用實驗設計法，探討濕氧蒸爆（Wet oxidative steam explosion）反應時間與氧氣含量對半纖維素降解、木質素移除與纖維素酵素糖化的影響。蒸爆的溫度為190℃，反應時間與氧氣濃度的範圍分別為5~20 min與0~60%。研究結果顯示，濕氧蒸爆主要造成半纖維素的降解；木質素與灰份的移除及纖維素糖化率的提升，則需將蒸爆過的稻殼施以鹼性過氧化處理(1% H2O2, pH 11.5, 80℃,45 min, 固液比8% w/w)才會有效。蒸爆與鹼性過氧化處理後，各蒸爆條件的灰份移除率均超過95%，並不隨蒸爆強度的改變而有顯著的變化；木質素的移除率則隨蒸爆強度的增加而提升，增加氧氣濃度的效應尤其顯著，當氧氣濃度為60%時，木質素的移除率可達86%。本研究最佳糖化率接近96%，前處理條件為190℃, 20 min, 60% 氧氣的溼氧蒸爆搭配鹼性過氧化處理，但是這個蒸爆條件會導致半纖維素過度降解，使木寡糖產率偏低。若要兼顧木寡糖的生產，190℃, 12.5 min, 30%氧氣是較好的溼氧蒸爆條件，木寡糖產率71%，而纖維素糖化率較低的問題應該可以藉由鹼性過氧化處理條件的改變來解決。

關鍵字

木質纖維素 ； 稻殼 ； 濕氧蒸煮爆碎法 ； 前處理 ； 酵素水解

並列摘要

Lignocellulosic materials, such as agricultural residues and energy plants, are the most abundant renewable biomass on earth. They are potential feed stock for the manufacturing of biofuels and chemicals. However, the effective utilization of lignocellulosic materials is limited by the close association of the three main components-cellulose, hemicellulose and lignin. Adequate pretreatment processes are therefore needed to fractionate the biomass, so that a more complete utilization of the biomass can be achieved.
In this study, rice hulls were subjected to wet oxidative (WO) steam explosion , followed by an alkaline peroxide (AP) treatment (1% H2O2, pH 11.5, 80 ℃, 45 min, solid to liquid ratio 8% w/w). The effects of WO steam explosion residence time and oxygen content on xylan and lignin removal and enzymatic saccharification were studied using experimental design. The WO steam explosion experiments were performed at 190℃, with residence time ranging from 5 min to 20 min and oxygen content from 0% to 60%. The results indicate that the main effect of WO steam explosion was the solubilisation of hemicellulose, which alone was not sufficient to achieve a high enzymatic digestibility. An additional AP treatment was necessary to remove most lignin and ash from the WO steam exploded rice hulls, and to significantly improve the enzymatic digestibility. With the combination of WO steam explosion and AP treatment, > 95% of the ash was removed under all the WO steam explosion conditions. The removal of lignin, on the other hand, increased with increasing severity of WO steam explosion, and the effect of oxygen concentration was especially significant. The lignin removal reached 85% when the WO steam explosion was performed with 60% oxygen. The enzymatic digestibility also increased with increasing severity of WO steam explosion, reaching a maximum of about 96 % when a 20 min residence time and 60% oxygen were used. However, under this WO steam explosion condition, the yield of xylooligosaccharides was low (about 50%), as a large portion of xylan was converted to xylose. When xylooligosaccharides are considered as a co-product, a milder WO steam explosion condition should be used. In the present study, the highest yield of xylooligosaccharides (71%) was obtained at the WO steam explosion condition of 190℃, 12.5 min with 30% oxygen.

並列關鍵字

lignocellulose ； rice hulls ； Wet Oxidative Steam Explosion ； pretreatment ； enzymatic hydrolysis

參考文獻

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