芒草是優(yōu)質(zhì)的生物能源植物,由于其生物質(zhì)產(chǎn)量巨大,可用于木質(zhì)纖維乙醇和相關(guān)化學(xué)產(chǎn)品的生產(chǎn)。目前纖維素乙醇已作為優(yōu)良的添加劑加入到汽油中以減少碳排放。纖維素乙醇的生產(chǎn)大體包含三個主要步驟:理化預(yù)處理部分裂解植物細(xì)胞壁聚合物,纖維素復(fù)合酶降解產(chǎn)生可溶性糖,酵母發(fā)酵生產(chǎn)乙醇。然而,木質(zhì)纖維素固有的抗降解屏障,不僅使生產(chǎn)成本高、還會對環(huán)境產(chǎn)生第二次污染。木質(zhì)纖維素的抗降解屏障主要由細(xì)胞壁組分,聚合物特性以及復(fù)雜細(xì)胞壁網(wǎng)絡(luò)結(jié)構(gòu)共同決定。盡管生物質(zhì)的孔隙度是決定木質(zhì)纖維素酶解產(chǎn)糖產(chǎn)醇效率的重要綜合因子,但有關(guān)植物細(xì)胞壁聚合物特性和細(xì)胞壁網(wǎng)絡(luò)是如何影響孔隙度的報導(dǎo)甚少。此外,基于細(xì)胞壁結(jié)構(gòu)的多樣性,不同的預(yù)處理對細(xì)胞壁組分、多聚物的特性以及鍵鏈接方式的影響尚缺乏一個優(yōu)化評判標(biāo)準(zhǔn)。本研究首次利用DY 11和DB 15染料代替?zhèn)鹘y(tǒng)DO 15和DB 1染料作為西蒙染色法的染色劑,并對新染色方法的穩(wěn)定性及其在測量生物質(zhì)表面可及性中的應(yīng)用潛力進(jìn)行了評估。利用改進(jìn)后的染色方法,研究了芒草生物質(zhì)孔隙度對酶解效率的影響。進(jìn)一步利用四組具有不同細(xì)胞壁組分的代表性芒草材料,利用熱水預(yù)處理（LHW）和酸堿預(yù)處理（H

【文章來源】：華中農(nóng)業(yè)大學(xué)湖北省 211工程院校 教育部直屬院校

【文章頁數(shù)】：163 頁

【學(xué)位級別】：博士

【文章目錄】：
摘要
Abstract
Abbreviations
1 Introduction
    1.1 Global energy situation
    1.2 Lignocellulose-based biofuels
        1.2.1 Opportunities for lignocellulosic biofuels production
        1.2.2 Challenges for lignocellulosic biofuels production
        1.2.3 Miscanthus,a dedicated bioenergy crop
    1.3 Plant cell wall
    1.4 Cell wall chemistry influencing cellulose accessibility and digestibility
    1.5 Wall polymers and their features influencing cellulose accessibility and digestibility
        1.5.1 Cellulose
        1.5.2 Hemicelluloses
        1.5.3 Lignin
        1.5.4 Pectins
        1.5.5 Proteins
    1.6 Pretreatment for enhancing lignocellulose accessibility and digestibility
        1.6.1 Alkali pretreatment
        1.6.2 Acid pretreatment
        1.6.3 Liquid hot water pretreatment
    1.7 Biomass surface area（porosity）
        1.7.1 Measurements of surface area/porosity
        1.7.2 Simons?Stain
        1.7.3 Congo red stain
        1.7.4 Enzyme adsorption
        1.7.5 Nitrogen adsorption
        1.7.6 Water Retention Value
    1.8 Enzymatic hydrolysis of lignocelluloses
        1.8.1 Inhibition of cellulase enzymes by hemicelluloses/lignin
        1.8.2 Application of additives（surfactants）to alleviate lignin inhibition
    1.9 Yeast fermentation for ethanol production
    1.10 Objectives of the study
2 Methods and materials
    2.1 Collection of plant materials
    2.2 Plant cell wall fractionation
    2.3 Colorimetric assay of hexoses,pentoses and uronic acids
    2.4 Total lignin assay
        2.4.1 Determination of acid-insoluble lignin
        2.4.2 Determination of acid-soluble lignin
    2.5 Quantification of lignin monomers by HPLC
    2.6 Hemicelluloses monosaccharides determination by GC-MS
        2.6.1 Sample preparation
        2.6.2 Standard solutions preparation
        2.6.3 TFA hydrolysis
        2.6.4 Derivatization of monosaccharides to alditol acetates
        2.6.5 GC-MS analytical conditions
    2.7 Detection of cellulose crystallinity index（CrI）
    2.8 Determination of cellulose degree of polymerization（DP）
        2.8.1 Sample preparation
        2.8.2 Cellulose DP assay
    2.9 Biomass characterization by microscopy and spectroscopy
        2.9.1 Scanning electron microscopy（SEM）
        2.9.2 Fourier transform infrared（FTIR）spectroscopy
    2.10 Measurement of biomass porosity
        2.10.1 Solvent exchange drying
        2.10.2 Dye preparation for Simons?stain
        2.10.3 Adsorption studies of Simons?stain
        2.10.4 Simons?stain assay
        2.10.5 Congo red staining
        2.10.6 Enzyme adsorption
        2.10.7 Nitrogen adsorption
        2.10.8 Water retention value
    2.11 Biomass pretreatments and enzymatic saccharification
        2.11.1 LHW pretreatment
2SO₄ pretreatment">        2.11.2 H₂SO₄ pretreatment
        2.11.3 NaOH pretreatment
        2.11.4 Direct enzymatic hydrolysis
        2.11.5 Surfactant-assisted enzymatic hydrolysis
    2.12 Yeast fermentation and ethanol estimation
    2.13 Statistical interpretation of correlation coefficients
3 Results
    3.1 Adsorption studies for optimal parameters of Simons?staining technique
    3.2 Optimal LHW and chemical pretreatments for enhancing biomass enzymatic saccharification
    3.3 Tween-80 co-supply for a complete biomass enzymatic hydrolysis
    3.4 Optimal pretreatments and Tween-80 co-supply for the highest bioethanol production
    3.5 Large extractions of wall polymers under optimal pretreatments
    3.6 Distinct alterations of wall polymer features from optimal pretreatments
    3.7 Characteristic changes of biomass morphology and wall polymer linkages from optimal pretreatments
    3.8 A significant increase of biomass porosity under optimal pretreatments
    3.9 A key factor of biomass porosity on biomass enzymatic saccharification
    3.10 Integrative impact on biomass enzymatic saccharification
    3.11 The mechanism for complete biomass saccharification and highest bioethanol production
4 Discussion
5 Conclusion
6 Summary and future prospects
    6.1 Summary
    6.2 Prospects
References
Appendix1:Reagents/buffers formulation
Appendix2:Regression equations of standard curve
Appendix3:Profile
Appendix4:Publications
Acknowledgement



本文編號：3059256