木質纖維素生物質可用於生產乙醇，一種在原油有限的現實中具前景的替代能源。在轉化過程中分成兩個程序：水解木質纖維素生物質中的纖維素以產生還原糖以及使糖發酵生成乙醇。使用目前的技術從木質纖維素原料生產乙醇的成本相當高，主要的困難點在低產率以及水解的高成本。相當多的研究致力於提高木質纖維素原料的水解效率，前處理以移除木質纖維素原料中的木質素和半纖維素可以有效提升水解纖維素的效率。然而木質纖維素生物質主要成分的緊密連結造成物理與化學上的阻礙，限制了纖維素的水解與木質素、半纖維素的分離。因此，根據選擇用來進行串聯水解和發酵步驟的裝置，我們需要選擇不同的前處理方法和條件。目前研究著重探究新的前處理方法，將超臨界二氧化碳(scCO2)與其他前處理方法依序使用，例如超音波、鹼性過氧化氫(H2O2)與臭氧，在溫和條件下(80-180 oC與45-120分鐘)在批次式反應器中前處理木質纖維素生物質。
　　我們提出一種嶄新的前處理方法，依序使用scCO2與鹼性H2O2在溫和條件下前處理甘蔗渣，此方法產率相較單獨使用scCO2、超音波或H2O2以及串聯scCO2與超音波的前處理方法好上兩倍。使用scCO2前處理可得到高含量的纖維素與半纖維素，但仍有不溶於酸的木質素。使用超音波或H2O2前處理可部分解聚木質素，然而無法將纖維素從木質素中分離。將酵素水解後的液體產物以HPLC分析以及將固體殘渣以SEM觀察，結果顯示出scCO2與H2O2的強大協同性。
　　當甘蔗渣依序使用scCO2與臭氧前處理後，葡萄糖回收率由15-20%顯著提升到40-65%。原因可能是scCO2爆破前處理提高了木質纖維素原料的消化率。scCO2爆破前處理在高壓爐中在80-120 oC、CO2 壓力20.6 MPa下反應30分鐘，接著以固定床反應器在室溫下進行臭氧前處理。我們研究兩個主要的變數：scCO2爆破前處理的溫度與臭氧前處理的時間。甘蔗渣在前處理組合後提高了自纖維中獲取纖維素的能力以及酵素水解的效率，使纖維素含量提升與木質素含量下降，值得一提的是糠醛與羥甲基糠醛在前處理中並未偵測到。因此，總括來說結合scCO2爆破前處理與臭氧前處理是一個提昇生物質原料葡萄糖回收率的有效方法。
　　我們提出一種新的木屑前處理方法，稱為CO2壓縮液態THF溶液前處理，以提高生質乙醇生產時所需的纖維素含量。如果使用最佳化的酵素水解條件，此前處理方法使用THF混溶使用CO2壓縮後的液態酸性溶液可從木屑中得到高達90%的葡萄糖回收率。我們使用CCD找出最佳化的前處理條件，所有因子皆顯著影響葡萄糖回收率。我們建立一個四次多項式模型表示葡萄糖回收率，使用響應曲面法進行多重回歸分析決定最佳化前處理條件。最佳化條件為水:THF=1:2、溫度185 oC、CO2 壓力11.7MPa與前處理時間2小時，得到的葡萄糖回收率為84.1%。實驗驗證最佳化條件與模型預測符合。此前處理方法效率高的原因可歸於非常高的木質素移除，組成分析支持這項假設。接著，經由使高揮發性的THF揮發，幾乎純的木質素產物會沉澱，可回收使用。
　　另一項研究中，我們使用CCD找出壓縮CO2前處理鳳眼藍後以提高酵素水解葡萄糖回收率的最佳化壓力、溫度與前處理時間，所有因子皆顯著影響葡萄糖回收率。我們建立一個四次多項式模型表示葡萄糖回收率，使用響應曲面法進行多重回歸分析預測並決定最佳化前處理條件。最佳化條件為溫度140 oC、CO2 壓力5.8MPa與前處理時間90分鐘，得到的葡萄糖回收率為96.5%。實驗驗證最佳化條件與模型預測符合。得到的結果顯示壓縮CO2前處理可以避免產生抑制發酵的物質，例如5-羥甲基糠醛，並構成提升酵素水解鳳眼蘭效率的方法。接著使用實驗數據中得到的所有必需輸入值進行簡化的生命週期評估，結果顯示可以得到明顯的化石燃料消耗下降以及減少對人類健康與環境的衝擊。

Lignocellulosic biomass can be utilized to produce ethanol, a promising alternative energy source for the limited crude oil. There are mainly two processes involved in the conversion: hydrolysis of cellulose in the lignocellulosic biomass to produce reducing sugars, and fermentation of the sugars to ethanol. The cost of ethanol production from lignocellulosic material is relatively high based on current technologies, and the main challenges are the low yield and high cost of the hydrolysis process. Considerable research efforts have been made to improve the hydrolysis of lignocellulosic materials. Pretreatment of lignocellulosic materials to remove lignin and hemicellulose can significantly enhance the hydrolysis of cellulose. However, physical and chemical barriers caused by the close association of the main components of lignocellulosic biomass, hinder the hydrolysis of cellulose and hemicellulose and lignin fraction thus, different pretreatment methods and conditions should be chosen according to the process configuration selected for the subsequent hydrolysis and fermentation steps. The present work aims at exploring new pretreatment approaches using sequential combinations of supercritical CO2 (scCO2) and other pretreatment means such as ultrasound, alkaline hydrogen peroxide and ozonolysis at mild conditions (80-180 oC and 45-120 min) to pretreat lignocellulosic biomass in a batch reactor.
An innovative method for pretreatment of sugarcane bagasse using sequential combination of supercritical CO2 (scCO2) and alkaline hydrogen peroxide (H2O2) at mild conditions was proposed. Yields of cellulose was found to be two times superior when compared to the individual pretreatment with scCO2, ultrasound, or H2O2 and the sequential combination of scCO2 and ultrasound. Pretreatment with scCO2 obtained high amounts of cellulose and hemicellulose but also acid-insoluble lignin. Pretreatment with ultrasound or H2O2 could partly depolymerize lignin, however, could not separate cellulose from lignin. HPLC analysis of liquid products via enzymatic hydrolysis and characterization of solid residues by SEM revealed strong synergetic effects in the sequential combination of scCO2 and H2O2.
A significant increase in glucose recovery from 15-20 to 40-65% was obtained when sugarcane bagasse was sequentially pretreated using scCO2 followed by ozonolysis. The reason for this can be attributed to an increased lignocellulosic material digestibility by scCO2 explosion pretreatment that was conducted in a high pressure autoclave at 80-120 oC, 20.6 MPa of CO2 pressure and 30 min while the ozonolysis of scCO2-pretreated sugarcane bagasse was carried out in a fixed bed reactor at room temperature. The effects of two major parameters, temperature of scCO2 explosion pretreatment and time for ozonolysis, were studied. An increased access of cellulose to the cellulose fiber and an increased enzymatic hydrolysis led to an increase in the cellulose fraction while decreasing the lignin content for the combined pretreatment of sugarcane bagasse. It is also noteworthy that furfural and hydroxymethyl furfural were not detected of the pretreatments. Thus it can be concluded that the sequential pretreatment of sugarcane bagasse using scCO2 explosion followed by ozonolysis is an efficient way to improve glucose recovery from biomass feedstocks.
A new pretreatment for wood dust called CO2 compressed aqueous THF solution pretreatment was proposed to enhance cellulose in the subsequent process of bioethanol production. This pretreatment approach employed THF miscible with aqueous acidity solution by CO2-compressed to obtain up 90% glucose recovery from wood dust if coupled with enzymatic hydrolysis at the optimum condition. A central composite design was used to optimize the pretreatment conditions. All factors were found to affect glucose recovery significantly. A quadratic polynomial equation was modelled for glucose recovery by multiple regression analysis using response surface methodology to determine the optimum pretreatment condition. A glucose recovery of 84.1% for the optimum condition at a water:THF ratio of 1:2, a temperature of 190 oC, a CO2 pressure of 11.7 MPa and a pretreated time of 2 h. Experimental verification of the optimum conditions showed glucose recovery well within the estimated value of the model. High efficiency of this pretreatment approach could be attributed to a very high lignin removal which is supported by compositional analysis. Subsequently, nearly pure lignin product can be precipitated by evaporation of volatile THF for recovery and recycling.
The other work optimized the effects of pressure, temperature, and pretreated time in the pressurized CO2 pretreatment of water hyacinth to enhance glucose recovery following enzymatic hydrolysis using a central composite design. All of the factors were found to significantly affect glucose recovery. A quadratic polynomial equation was modelled to predict and determine the optimum conditions for glucose recovery by multiple regression analysis using response surface methodology. The optimum conditions for the pretreatment of water hyacinth were obtained at CO2 pressure of 5.8 MPa and 140 oC for 90 min, yielding a glucose recovery of 96.5 %. Experimental verification of the optimum conditions showed that the glucose recovery was well within the predicted value. The obtained results indicate that the pressurized CO2 pretreatment avoids formation of the inhibitors for fermentation such as furfural and 5-hydroxymethylfurfural and constitutes an efficient way to improve enzymatic hydrolysis from water hyacinth. Following a simplified life cycle assessment using all of the required input values from our experimental data, it was demonstrated that a significant fossil fuel reduction, as well as less human health and ecosystem impacts, could be achieved.

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