用[胆碱][氨基酸]离子液体预处理木质纤维素生物质的研究
|
摘要
随着全球能源危机的频繁爆发和环境污染的加剧，以清洁、可再生的生物燃料替代化石能源已受到人们的广泛关注。其中，以来源广泛、廉价、可再生的木质纤维素生物质如农业废弃物为原料生产生物燃料最具应用前景。由于其天然的复杂结构特性，木质纤维素生物质具有超强的化学或生物降解抗性，故通常需要在降解前进行预处理。近年来，离子液体由于其优异的物理化学性质尤其是其较强的溶解能力，在生物质预处理领域表现出广阔的应用前景。然而，传统的咪唑、吡啶类离子液体存在合成原料不可再生、合成工艺复杂且环境不友好、毒性大、生物降解性差及其预处理过程受水干扰大等缺点。最近本课题组合成了一类新型、低毒、易生物降解、可再生的[胆碱][氨基酸]离子液体。迄今，尚未见这类新型、环境友好的离子液体用于木质纤维素预处理的相关报道。基于以上情况，本论文首先研究了木质纤维素生物质中的主要组分（纤维素、木聚糖及木质素）在[胆碱][氨基酸]离子液体中的溶解性，并阐明了溶解过程对各组分结构与性质的影响；在此基础上，首次探讨了这类可再生离子液体预处理农业废弃生物质水稻秸秆以提高其酶解效率的可行性，并揭示了各因素对木质素提取率、酶解效率的影响规律；随后在离子液体中添加部分绿色、廉价的水，研究其对水稻秸秆预处理的影响规律，并结合相关显微分析技术，首次揭示了[胆碱][氨基酸]离子液体水溶液预处理水稻秸秆的机制；最后，拓展了该类离子液体预处理的应用范围，探讨其预处理甘蔗渣的可行性；基于此，建立绿色、高效、简便、经济的农业废弃生物质的预处理工艺。
溶解性研究表明，大多数[胆碱][氨基酸]离子液体具有优良的木质素溶解能力，而对木聚糖的溶解能力较差，并且几乎不能溶解微晶纤维素。微晶纤维素经[胆碱][氨基酸]离子液体处理后，其酶解效率均有明显提高，这主要是预处理后微晶纤维素表面粗糙度及表面积增加的缘故，而非微晶纤维素晶体结构的变化导致的。傅立叶变换红外光谱（FTIR）及热重（TG）分析研究表明，在[胆碱][氨基酸]离子液体溶解处理过程中，木聚糖和木质素的骨架结构未发生明显变化，仅部分酯键发生断裂。上述研究表明，[胆碱][氨基酸]离子液体具有选择性提取木质素、高效预处理木质纤维素生物质原料的应用潜力。
研究结果表明，所考察的8种[胆碱][氨基酸]离子液体均为高效的水稻秸秆预处理溶剂。该类离子液体预处理提高水稻秸秆酶解效率的原因主要在于木质素的选择性去除，而非纤维素结晶度的降低。离子液体的阴离子结构与性质、预处理温度和时间对木质素提取率和多糖降解度的影响显著。最适的预处理离子液体、温度及时间分别是[胆碱][赖氨酸]（[Ch][Lys]），90℃及5h。在该条件下，木质素提取率达49.7%，残渣酶解反应的葡萄糖及木糖释放初速度分别为2.35及0.51mg/(mL h)，葡萄糖及木糖收率分别为84.0%和42.1%。[Ch][Lys]在水稻秸秆预处理中表现出优异的可重复利用性。
[胆碱][氨基酸]离子液体对水稻秸秆的预处理过程具有优异的耐水性。在离子液体中加入绿色、廉价的水，不仅其木质素提取能力未明显减弱，还极大地降低了离子液体的粘度，便于操作；更使成本及多糖损失减少。除[胆碱][天冬氨酸]（[Ch][Asp]）及[胆碱][谷氨酸]（[Ch][Glu]）外，其它16种50%[胆碱][氨基酸]离子液体水溶液预处理均能显著提高水稻秸秆的酶解效率。借助共聚焦激光扫描显微镜（CLSM）、透射电子显微镜（TEM）和原子力显微镜（AFM）等微观分析技术，系统地研究了该离子液体预处理水稻秸秆的机制。结果表明，在50%[Ch][Lys]水溶液预处理过程中，水稻秸秆茎部细胞壁中木质素的去除量随着预处理时间的延长而增大；表皮附近维管束中的厚壁细胞壁发生了明显的溶胀；细胞壁的细胞角隅（CC）、复合胞间层（CML）中的木质素比次生壁2层（S2）中的更易被去除；木质素的去除增大了木聚糖的可及性；预处理后，细胞壁表面的粗糙度和亲水性显著增大。
预处理溶剂的碱性和其木质素提取能力直接相关，但碱性仅是[胆碱][氨基酸]离子液体理化性质中对其优异的木质素提取能力有贡献的因素之一。木质素的去除极大地提高了底物的比表面积和孔体积，从而增大了酶分子对多糖的可及性，导致多糖降解度的增大。通过控制预处理强度（离子液体含量和预处理温度及时间），既可增大多糖降解度，又能减少多糖损失，提高还原糖收率，并降低能耗。最适的预处理溶剂、温度及时间分别为20%[Ch][Lys]水溶液、90℃及1h。在该最适条件下，木质素提取率为37.8%；在后续酶解反应中，残渣的葡萄糖和木糖释放初速度分别为1.34和0.48mg/(mL h)，其收率分别达81.4%和47.8%。
所选用的6种[胆碱][氨基酸]离子液体均能高效预处理甘蔗渣。与水稻秸秆的预处理过程类似，该类离子液体能选择性从甘蔗渣中提取部分木质素，从而导致多糖酶解效率显著提高。非常有意思的是，经[Ch][Lys]预处理后，甘蔗渣的酶解效率与原料尺寸无相关性。类似地，虽然水的添加降低了[Ch][Lys]的脱木质素能力，但对后续甘蔗渣的酶解效率影响甚微。我们成功地放大了该预处理工艺，未经粉碎的甘蔗渣（5%固体添加量，w/w）经50g50%[Ch][Lys]水溶液于90℃下预处理6h，回收残渣酶解后，葡萄糖、木糖收率分别达80%和84%。研究发现，通过简单、原子经济的方法制备所得的[胆碱][氨基酸]离子液体水溶液同样具有优异的木质纤维素生物质预处理效果。且微量的反应物杂质对离子液体的预处理效果影响甚微。
本研究不仅丰富了离子液体预处理木质纤维素生物质的基础理论知识，还开辟了一条绿色、高效、简便、经济的农业废弃生物质预处理新途径。
In recent years, with the frequent eruption of the energy crisis and the increasingconcerns about environment pollution on earth, clean and renewable biofuels as an alternativeof fossil energy sources have attracted extensive interest. Biofuels production from abundant,cheap and renewable lignocellulosic biomass such as agricultural waste is promising.Lignocellulosic biomass is highly recalcitrant to chemical and biological degradation due toits natural complicated structure. Therefore, pretreatment is essential prior to degradation.Recently, ionic liquids (ILs) have emerged as a promising class of solvents for pretreatmentof lignocellulosic biomass owing to their excellent physiochemical properties, especially thestrong ability to dissolve various compounds. However, the traditional imidazolium orpyridinium ILs have been proved to be highly toxic and poorly biodegradable; in addition, thestarting materials for the synthesis of these ILs are non-renewable, the ILs preparationprocesses are tedious and environmentally unfriendly, and the processes of biomasspretreatment with these ILs are usually not tolerant to moisture. Recently, a type of novel andrenewable cholinium amino acids ([Ch][AA]) ILs with low toxicity and excellentbiodegradability has been synthesized by our group. To date, no work has been done on thepretreatment of lignocellulosic biomass by these new and environmentally friendly ILs. Thus,the solubility of the main components of lignocellulosic biomass (cellulose, xylan and lignin)in these [Ch][AA] ILs was determined and the effect of the dissolution process on thestructures and properties of the components was investigated in this dissertation. Then, thefeasibility of agricultural waste biomass–rice straw pretreatment with [Ch][AA] ILs wasexplored to enhance the enzymatic hydrolysis of the residues for the first time. Also, theeffects of various factors on the lignin extractability and the enzymatic hydrolysis efficiencyof the residues were examined. Furthermore, the effect of the addition of greener and cheaperwater on ILs pretreatment efficiencies was studied, and the mechanism of rice strawpretreatment using [Ch][AA] ILs aqueous solution was revealed by microscopic techniquesfor the first time. Finally, the feasibility of sugarcane bagasse pretreatment with [Ch][AA] ILswas also explored to extend the application potential of this process. Agreen, efficient, simpleand economic process of agricultural waste biomass pretreatment was developed.
It was shown that most of these [Ch][AA] ILs had good abilities to dissolve lignin, andthe solubility of xylan in these ILs was relatively lower, and microcrystalline cellulose (MCC)was scarcely soluble. The enzymatic hydrolysis of MCC was improved significantly after ILspretreatment, which was attributed to the rougher and larger surface area of the pretreated MCC rather than the change of its crystal structure. Fourier transform infrared spectrum(FTIR) and thermal gravimetric (TG) analysis indicated that the skeleton structures of xylanand lignin were not damaged markedly during the dissolution in ILs, except for the breakageof partial ester bonds. The above results indicate that [Ch][AA] ILs may be a type of potentialand good solvent for highly efficient lignocellulosic biomass pretreatment by selectiveextraction of lignin.
Eight [Ch][AA] ILs examined were demonstrated to be excellent solvents for rice strawpretreatment. The enhancement of enzymatic hydrolysis of polysaccharides after pretreatmentderived mainly from selective delignification, instead of changes in cellulose crystallinity.Lignin extractability and polysaccharides digestibility were significantly influenced by theanion structures and properties of the ILs, pretreatment temperature and time. The optimal IL,pretreatment temperature and time were cholinium lysinate ([Ch][Lys]),90℃and5h,respectively. Under the optimal conditions,49.7%of lignin was removed; the sugar initialrelease rates of2.35mg/(mL h) for glucose and0.51mg/(mL h) for xylose, and the sugaryields of84.0%for glucose and42.1%for xylose were achieved in the enzymatic hydrolysisof the residues. The IL [Ch][Lys] showed excellent reusability in rice straw pretreatment.
It was found that the process of rice straw pretreatment with [Ch][AA] ILs was highlytolerant to moisture. The addition of cheap and green water into ILs not only led to noconsiderable decrease in the dissolution ability of the ILs to lignin, but also significantlylowered their viscosity, which made handling easier; additionally, even the cost and thepolysaccharides losses were reduced. The enzymatic hydrolysis efficiency of rice straw wasremarkably enhanced after the pretreatment with other sixteen50%[Ch][AA] ILs aqueoussolutions, with the exception of cholinium aspartate ([Ch][Asp]) and cholinium glutamate([Ch][Glu]). The mechanism of rice straw pretreatment with [Ch][Lys] aqueous solution wasinvestigated by using confocal laser scanning microscopy (CLSM), transmission electronmicroscopy (TEM) and atomic force microscope (AFM). It was revealed that duringpretreatment with50%[Ch][Lys] aqueous solution, lignin removal from cell walls of the ricestraw stem increased with the elongation of pretreatment time; swelling occurred insclerenchyma cell walls of vascular bundles near the epidermis; lignin in cell corner (CC) andcompound middle lumen (CML) of cell walls was easier to be extracted than that in thesecondary cell wall2(S2); extensive delignification resulted in the increase of xylanaccessibility; and the surface of cell walls become rougher and more hydrophilic.
There is a clear correlation between the basicity of the pretreatment solvent and itsdelignification capacity, but the basicity is just one of the physiochemical properties of [Ch][AA] ILs that contribute to their excellent delignification capacities. Besides, it wasproved that lignin removal during pretreatment led to significant increases in surface area andpore volume of rice straw, which substantially improved the polysaccharides accessibility toenzymes and thus enhanced polysaccharides digestion. By carefully controlling thepretreatment severity (IL content, temperature and duration), the balance between maximizingthe polysaccharides digestibility and minimizing the polysaccharides losses could be reached,leading to high sugar yield and low energy consumption. The optimal pretreatment solvent,temperature and time were20%[Ch][Lys] aqueous solution,90℃and1h, respectively.Under the optimal conditions,37.8%of lignin was removed, and the initial sugar releasingrates of1.34mg/(mL h) for glucose and0.48mg/(mL h) for xylose, and the sugar yields of81%for glucose and48%for xylose were obtained in the enzymatic hydrolysis of theresidues.
Six [Ch][AA] ILs tested were found to be effective for sugarcane bagasse pretreatment.Similarly, lignin was selectively removed from sugarcane bagasse by these ILs, thus leadingto substantial improvement of enzymatic hydrolysis of the residues. Interestingly, it wasfound that the efficiency of enzymatic hydrolysis of sugarcane bagasse after [Ch][Lys]pretreatment was independent on the substrate sizes. Also, the addition of water into [Ch][Lys]did not exert a negative effect on the subsequent enzymatic hydrolysis efficiency of theresidues, in spite of the decline in the delignification capacity. The process of sugarcanebagasse pretreatment without comminution or size reduction was successfully scaled up andsugar yields of80%for glucose and84%for xylose were obtained in the enzymatichydrolysis of the residues after pretreatment with a biomass loading of5%(w/w) by50g50%[Ch][Lys] aqueous solution at90℃for6h.[Ch][AA] ILs prepared by a simple andatom-economic approach were also found to be highly efficient for lignocellulosic biomasspretreatment. And the reactant impurities in the IL had a marginal effect on its pretreatmenteffectiveness.
This study not only enriches the knowledge of ILs pretreatment of lignocellulosicbiomass, but also provides a green, highly efficient, simple and economic route foragricultural waste biomass pretreatment.
溶解性研究表明，大多数[胆碱][氨基酸]离子液体具有优良的木质素溶解能力，而对木聚糖的溶解能力较差，并且几乎不能溶解微晶纤维素。微晶纤维素经[胆碱][氨基酸]离子液体处理后，其酶解效率均有明显提高，这主要是预处理后微晶纤维素表面粗糙度及表面积增加的缘故，而非微晶纤维素晶体结构的变化导致的。傅立叶变换红外光谱（FTIR）及热重（TG）分析研究表明，在[胆碱][氨基酸]离子液体溶解处理过程中，木聚糖和木质素的骨架结构未发生明显变化，仅部分酯键发生断裂。上述研究表明，[胆碱][氨基酸]离子液体具有选择性提取木质素、高效预处理木质纤维素生物质原料的应用潜力。
研究结果表明，所考察的8种[胆碱][氨基酸]离子液体均为高效的水稻秸秆预处理溶剂。该类离子液体预处理提高水稻秸秆酶解效率的原因主要在于木质素的选择性去除，而非纤维素结晶度的降低。离子液体的阴离子结构与性质、预处理温度和时间对木质素提取率和多糖降解度的影响显著。最适的预处理离子液体、温度及时间分别是[胆碱][赖氨酸]（[Ch][Lys]），90℃及5h。在该条件下，木质素提取率达49.7%，残渣酶解反应的葡萄糖及木糖释放初速度分别为2.35及0.51mg/(mL h)，葡萄糖及木糖收率分别为84.0%和42.1%。[Ch][Lys]在水稻秸秆预处理中表现出优异的可重复利用性。
[胆碱][氨基酸]离子液体对水稻秸秆的预处理过程具有优异的耐水性。在离子液体中加入绿色、廉价的水，不仅其木质素提取能力未明显减弱，还极大地降低了离子液体的粘度，便于操作；更使成本及多糖损失减少。除[胆碱][天冬氨酸]（[Ch][Asp]）及[胆碱][谷氨酸]（[Ch][Glu]）外，其它16种50%[胆碱][氨基酸]离子液体水溶液预处理均能显著提高水稻秸秆的酶解效率。借助共聚焦激光扫描显微镜（CLSM）、透射电子显微镜（TEM）和原子力显微镜（AFM）等微观分析技术，系统地研究了该离子液体预处理水稻秸秆的机制。结果表明，在50%[Ch][Lys]水溶液预处理过程中，水稻秸秆茎部细胞壁中木质素的去除量随着预处理时间的延长而增大；表皮附近维管束中的厚壁细胞壁发生了明显的溶胀；细胞壁的细胞角隅（CC）、复合胞间层（CML）中的木质素比次生壁2层（S2）中的更易被去除；木质素的去除增大了木聚糖的可及性；预处理后，细胞壁表面的粗糙度和亲水性显著增大。
预处理溶剂的碱性和其木质素提取能力直接相关，但碱性仅是[胆碱][氨基酸]离子液体理化性质中对其优异的木质素提取能力有贡献的因素之一。木质素的去除极大地提高了底物的比表面积和孔体积，从而增大了酶分子对多糖的可及性，导致多糖降解度的增大。通过控制预处理强度（离子液体含量和预处理温度及时间），既可增大多糖降解度，又能减少多糖损失，提高还原糖收率，并降低能耗。最适的预处理溶剂、温度及时间分别为20%[Ch][Lys]水溶液、90℃及1h。在该最适条件下，木质素提取率为37.8%；在后续酶解反应中，残渣的葡萄糖和木糖释放初速度分别为1.34和0.48mg/(mL h)，其收率分别达81.4%和47.8%。
所选用的6种[胆碱][氨基酸]离子液体均能高效预处理甘蔗渣。与水稻秸秆的预处理过程类似，该类离子液体能选择性从甘蔗渣中提取部分木质素，从而导致多糖酶解效率显著提高。非常有意思的是，经[Ch][Lys]预处理后，甘蔗渣的酶解效率与原料尺寸无相关性。类似地，虽然水的添加降低了[Ch][Lys]的脱木质素能力，但对后续甘蔗渣的酶解效率影响甚微。我们成功地放大了该预处理工艺，未经粉碎的甘蔗渣（5%固体添加量，w/w）经50g50%[Ch][Lys]水溶液于90℃下预处理6h，回收残渣酶解后，葡萄糖、木糖收率分别达80%和84%。研究发现，通过简单、原子经济的方法制备所得的[胆碱][氨基酸]离子液体水溶液同样具有优异的木质纤维素生物质预处理效果。且微量的反应物杂质对离子液体的预处理效果影响甚微。
本研究不仅丰富了离子液体预处理木质纤维素生物质的基础理论知识，还开辟了一条绿色、高效、简便、经济的农业废弃生物质预处理新途径。
In recent years, with the frequent eruption of the energy crisis and the increasingconcerns about environment pollution on earth, clean and renewable biofuels as an alternativeof fossil energy sources have attracted extensive interest. Biofuels production from abundant,cheap and renewable lignocellulosic biomass such as agricultural waste is promising.Lignocellulosic biomass is highly recalcitrant to chemical and biological degradation due toits natural complicated structure. Therefore, pretreatment is essential prior to degradation.Recently, ionic liquids (ILs) have emerged as a promising class of solvents for pretreatmentof lignocellulosic biomass owing to their excellent physiochemical properties, especially thestrong ability to dissolve various compounds. However, the traditional imidazolium orpyridinium ILs have been proved to be highly toxic and poorly biodegradable; in addition, thestarting materials for the synthesis of these ILs are non-renewable, the ILs preparationprocesses are tedious and environmentally unfriendly, and the processes of biomasspretreatment with these ILs are usually not tolerant to moisture. Recently, a type of novel andrenewable cholinium amino acids ([Ch][AA]) ILs with low toxicity and excellentbiodegradability has been synthesized by our group. To date, no work has been done on thepretreatment of lignocellulosic biomass by these new and environmentally friendly ILs. Thus,the solubility of the main components of lignocellulosic biomass (cellulose, xylan and lignin)in these [Ch][AA] ILs was determined and the effect of the dissolution process on thestructures and properties of the components was investigated in this dissertation. Then, thefeasibility of agricultural waste biomass–rice straw pretreatment with [Ch][AA] ILs wasexplored to enhance the enzymatic hydrolysis of the residues for the first time. Also, theeffects of various factors on the lignin extractability and the enzymatic hydrolysis efficiencyof the residues were examined. Furthermore, the effect of the addition of greener and cheaperwater on ILs pretreatment efficiencies was studied, and the mechanism of rice strawpretreatment using [Ch][AA] ILs aqueous solution was revealed by microscopic techniquesfor the first time. Finally, the feasibility of sugarcane bagasse pretreatment with [Ch][AA] ILswas also explored to extend the application potential of this process. Agreen, efficient, simpleand economic process of agricultural waste biomass pretreatment was developed.
It was shown that most of these [Ch][AA] ILs had good abilities to dissolve lignin, andthe solubility of xylan in these ILs was relatively lower, and microcrystalline cellulose (MCC)was scarcely soluble. The enzymatic hydrolysis of MCC was improved significantly after ILspretreatment, which was attributed to the rougher and larger surface area of the pretreated MCC rather than the change of its crystal structure. Fourier transform infrared spectrum(FTIR) and thermal gravimetric (TG) analysis indicated that the skeleton structures of xylanand lignin were not damaged markedly during the dissolution in ILs, except for the breakageof partial ester bonds. The above results indicate that [Ch][AA] ILs may be a type of potentialand good solvent for highly efficient lignocellulosic biomass pretreatment by selectiveextraction of lignin.
Eight [Ch][AA] ILs examined were demonstrated to be excellent solvents for rice strawpretreatment. The enhancement of enzymatic hydrolysis of polysaccharides after pretreatmentderived mainly from selective delignification, instead of changes in cellulose crystallinity.Lignin extractability and polysaccharides digestibility were significantly influenced by theanion structures and properties of the ILs, pretreatment temperature and time. The optimal IL,pretreatment temperature and time were cholinium lysinate ([Ch][Lys]),90℃and5h,respectively. Under the optimal conditions,49.7%of lignin was removed; the sugar initialrelease rates of2.35mg/(mL h) for glucose and0.51mg/(mL h) for xylose, and the sugaryields of84.0%for glucose and42.1%for xylose were achieved in the enzymatic hydrolysisof the residues. The IL [Ch][Lys] showed excellent reusability in rice straw pretreatment.
It was found that the process of rice straw pretreatment with [Ch][AA] ILs was highlytolerant to moisture. The addition of cheap and green water into ILs not only led to noconsiderable decrease in the dissolution ability of the ILs to lignin, but also significantlylowered their viscosity, which made handling easier; additionally, even the cost and thepolysaccharides losses were reduced. The enzymatic hydrolysis efficiency of rice straw wasremarkably enhanced after the pretreatment with other sixteen50%[Ch][AA] ILs aqueoussolutions, with the exception of cholinium aspartate ([Ch][Asp]) and cholinium glutamate([Ch][Glu]). The mechanism of rice straw pretreatment with [Ch][Lys] aqueous solution wasinvestigated by using confocal laser scanning microscopy (CLSM), transmission electronmicroscopy (TEM) and atomic force microscope (AFM). It was revealed that duringpretreatment with50%[Ch][Lys] aqueous solution, lignin removal from cell walls of the ricestraw stem increased with the elongation of pretreatment time; swelling occurred insclerenchyma cell walls of vascular bundles near the epidermis; lignin in cell corner (CC) andcompound middle lumen (CML) of cell walls was easier to be extracted than that in thesecondary cell wall2(S2); extensive delignification resulted in the increase of xylanaccessibility; and the surface of cell walls become rougher and more hydrophilic.
There is a clear correlation between the basicity of the pretreatment solvent and itsdelignification capacity, but the basicity is just one of the physiochemical properties of [Ch][AA] ILs that contribute to their excellent delignification capacities. Besides, it wasproved that lignin removal during pretreatment led to significant increases in surface area andpore volume of rice straw, which substantially improved the polysaccharides accessibility toenzymes and thus enhanced polysaccharides digestion. By carefully controlling thepretreatment severity (IL content, temperature and duration), the balance between maximizingthe polysaccharides digestibility and minimizing the polysaccharides losses could be reached,leading to high sugar yield and low energy consumption. The optimal pretreatment solvent,temperature and time were20%[Ch][Lys] aqueous solution,90℃and1h, respectively.Under the optimal conditions,37.8%of lignin was removed, and the initial sugar releasingrates of1.34mg/(mL h) for glucose and0.48mg/(mL h) for xylose, and the sugar yields of81%for glucose and48%for xylose were obtained in the enzymatic hydrolysis of theresidues.
Six [Ch][AA] ILs tested were found to be effective for sugarcane bagasse pretreatment.Similarly, lignin was selectively removed from sugarcane bagasse by these ILs, thus leadingto substantial improvement of enzymatic hydrolysis of the residues. Interestingly, it wasfound that the efficiency of enzymatic hydrolysis of sugarcane bagasse after [Ch][Lys]pretreatment was independent on the substrate sizes. Also, the addition of water into [Ch][Lys]did not exert a negative effect on the subsequent enzymatic hydrolysis efficiency of theresidues, in spite of the decline in the delignification capacity. The process of sugarcanebagasse pretreatment without comminution or size reduction was successfully scaled up andsugar yields of80%for glucose and84%for xylose were obtained in the enzymatichydrolysis of the residues after pretreatment with a biomass loading of5%(w/w) by50g50%[Ch][Lys] aqueous solution at90℃for6h.[Ch][AA] ILs prepared by a simple andatom-economic approach were also found to be highly efficient for lignocellulosic biomasspretreatment. And the reactant impurities in the IL had a marginal effect on its pretreatmenteffectiveness.
This study not only enriches the knowledge of ILs pretreatment of lignocellulosicbiomass, but also provides a green, highly efficient, simple and economic route foragricultural waste biomass pretreatment.
引文
[1] Luque R. Algal biofuels: the eternal promise?[J]. Energy Environ Sci,2010,3(3):254-257.
[2] J rgensen H., Kristensen J. B., Felby C. Enzymatic conversion of lignocellulose intofermentable sugars: challenges and opportunities [J]. Biofuel Bioprod Bior,2007,1(2):119-134.
[3] Chandra R., Bura R., Mabee W., et al. Substrate pretreatment: The key to effectiveenzymatic hydrolysis of lignocellulosics?[A]. Olsson L. Advances in BiochemicalEngineering/Biotechnology [C]. Springer Berlin Heidelberg, Biofuels,2007,108:67-93.
[4] David K., Ragauskas A. J. Switchgrass as an energy crop for biofuel production: a reviewof its ligno-cellulosic chemical properties [J]. Energy Environ Sci,2010,3(9):1182-1190.
[5] Agbor V. B., Cicek N., Sparling R., et al. Biomass pretreatment: fundamentals towardapplication [J]. BiotechnolAdv,2011,29(6):675-685.
[6] Olivier-Bourbigou H., Magna L., Morvan D. Ionic liquids and catalysis: recent progressfrom knowledge to applications [J]. Appl CatalA,2010,373(1):1-56.
[7] Saha B. C. Hemicellulose bioconversion [J]. J Ind Microbiol Biotechnol,2003,30(5):279-291.
[8] Gírio F., Fonseca C., Carvalheiro F., et al. Hemicelluloses for fuel ethanol: a review [J].Bioresour Technol,2010,101(13):4775-4800.
[9]Heinze T., Koschella A., Ebringerova A. Chemical functionalization of xylan: a shortreview [C]. ACS Symposium Series.2004.
[10] Sun S. N., Li M. F., Yuan T. Q., et al. Effect of ionic liquid pretreatment on the structureof hemicelluloses from corncob [J]. JAgri Food Chem,2012,60(44):11120-11127.
[11] Hendriks A., Zeeman G. Pretreatments to enhance the digestibility of lignocellulosicbiomass [J]. Bioresour Technol,2009,100(1):10-18.
[12] Avgerinos G., Wang D. I. C. Selective solvent delignification for fermentationenhancement [J]. Biotechnol Bioeng,1983,25(1):67-83.
[13] Sannigrahi P., Kim D., Jung S., et al. Pseudo-lignin and pretreatment chemistry [J].Energy Environ Sci,2011,4(4):1306–1310.
[14] Langan P., Gnanakaran S., Rector K. D., et al. Exploring new strategies for cellulosicbiofuels production [J]. Energy Environ Sci,2011,4(10):3820-3833.
[15] Lynd L. R., Laser M. S., Bransby D., et al. How biotech can transform biofuels [J].Nature Biotechnol,2008,26(2):169-172.
[16] Hamelinck C. N., Hooijdonk G. v., Faaij A. P. Ethanol from lignocellulosic biomass:techno-economic performance in short-, middle-and long-term [J]. Biomass Bioenerg,2005,28(4):384-410.
[17] Tong X., Ma Y., Li Y. Biomass into chemicals: conversion of sugars to furan derivativesby catalytic processes [J].Appl Catal, A,2010,385(1):1-13.
[18] Alvira P., Tomás-Pejó E., Ballesteros M., et al. Pretreatment technologies for an efficientbioethanol production process based on enzymatic hydrolysis: a review [J]. BioresourTechnol,2010,101(13):4851-4861.
[19] Yang B., Wyman C. E. Pretreatment: the key to unlocking low-cost cellulosic ethanol [J].Biofuels Bioprod Bioref,2008,2(1):26-40.
[20] Zhang Y. H. P., Ding S. Y., Mielenz J. R., et al. Fractionating recalcitrant lignocellulose atmodest reaction conditions [J]. Biotechnol Bioeng,2007,97(2):214-223.
[21] Hsu T., Ladisch R., Tsao G. Alcohol from cellulose [J]. Chem Intermediates,1980,1203(3):315-319.
[22] Zheng Y., Pan Z., Zhang R. Overview of biomass pretreatment for cellulosic ethanolproduction [J]. Int JAgric Biol Eng,2009,2(3):51-68.
[23] Zhao X., Zhang L., Liu D. Biomass recalcitrance. Part I: the chemical compositions andphysical structures affecting the enzymatic hydrolysis of lignocellulose [J]. BiofuelsBioprod Bioref Biofpr,2012,6(4):465-482.
[24] Mansfield S. D., Mooney C., Saddler J. N. Substrate and enzyme characteristics thatlimit cellulose hydrolysis [J]. Biotechnol Progress,1999,15(5):804-816.
[25] Cantarella M., Cantarella L., Gallifuoco A., et al. Comparison of different detoxificationmethods for steam-exploded poplar wood as a substrate for the bioproduction of ethanolin SHF and SSF [J]. Process Biochem,2004,39(11):1533-1542.
[26] Fu D., Mazza G., Tamaki Y. Lignin extraction from straw by ionic liquids and enzymatichydrolysis of the cellulosic residues [J]. JAgri Food Chem,2010,58(5):2915-2922.
[27] Lee S. H., Doherty T. V., Linhardt R. J., et al. Ionic liquid-mediated selective extractionof lignin from wood leading to enhanced enzymatic cellulose hydrolysis [J]. BiotechnolBioeng,2009,102(5):1368-1376.
[28] DeMartini J. D., Pattathil S., Avci U., et al. Application of monoclonal antibodies toinvestigate plant cell wall deconstruction for biofuels production [J]. Energy Environ Sci,2011,4(10):4332-4339.
[29] Yang B., Wyman C. E. BSA treatment to enhance enzymatic hydrolysis of cellulose inlignin containing substrates [J]. Biotechnol Bioeng,2006,94(4):611-617.
[30] S derstr m J., Pilcher L., Galbe M., et al. Two-step steam pretreatment of softwood withSO2impregnation for ethanol production [J]. Appl Biochem Biotechnol,2002,98(1-9):5-21.
[31] Sewalt V. J., Ni W., Blount J. W., et al. Reduced lignin content and altered lignincomposition in transgenic tobacco down-regulated in expression of L-phenylalanineammonia-lyase or cinnamate4-hydroxylase [J]. Plant Physiol,1997,115(1):41-50.
[32] Berlin A., Gilkes N., Kurabi A., et al. Enzymatic hydrolysis of steam-exploded andethanol organosolv-pretreated Douglas Fir by novel and commercial fungal-cellulases[J]. Appl Biochem Biotechnol,2005,121:219–230.
[33] Del Rio L. F., Chandra R. P., Saddler J. N. The effects of increasing swelling and anioniccharges on the enzymatic hydrolysis of organosolv-pretreated softwoods at low enzymeloadings [J]. Biotechnol Bioeng,2011,108(7):1549-1558.
[34] Tu M., Pan X., Saddler J. N. Adsorption of cellulase on cellulolytic enzyme lignin fromlodgepole pine [J]. JAgri Food Chem,2009,57(17):7771-7778.
[35] Kumar L., Arantes V., Chandra R., et al. The lignin present in steam pretreated softwoodbinds enzymes and limits cellulose accessibility [J]. Bioresour Technol,2012,103(1):201-208.
[36] Clark T. A., Mackie K. L. Fermentation inhibitors in wood hydrolysates derived from thesoftwood Pinus radiata [J]. J Chem Technol Biotechnol,1984,34(2):101-110.
[37] Heredia-Olea E., Perez-Carrillo E., Serna-Saldivar S. O. Effects of different acidhydrolyses on the conversion of sweet sorghum bagasse into C5and C6sugars and yeastinhibitors using response surface methodology [J]. Bioresour Technol,2012,119(September):216-223.
[38] Palmqvist E., Hahn-H gerdal B. Fermentation of lignocellulosic hydrolysates. II:inhibitors and mechanisms of inhibition [J]. Bioresour Technol,2000,74(1):25-33.
[39] Varga E., Klinke H. B., Réczey K., et al. High solid simultaneous saccharification andfermentation of wet oxidized corn stover to ethanol [J]. Biotechnol Bioeng,2004,88(5):567-574.
[40] Boussaid A., Esteghlalian A., Gregg D., et al. Steam pretreatment of Douglas-fir woodchips-can conditions for optimum hemicellulose recovery still provide adequate accessfor efficient enzymatic hydrolysis?[J]. Appl Biochem Biotechnol,2000,84(1):693-705.
[41] Brunecky R., Vinzant T. B., Porter S. F., et al. Redistribution of xylan in maize cell wallsduring dilute acid pretreatment [J]. Biotechnol Bioeng,2009,102(6):1537-1543.
[42] Grethlein H. E. The effect of pore size distribution on the rate of enzymatic hydrolysis ofcellulosic substrates [J]. Nature Biotechnol,1985,3(2):155-160.
[43] Tanaka M., Ikesaka M., Matsuno R., et al. Effect of pore size in substrate and diffusion ofenzyme on hydrolysis of cellulosic materials with cellulases [J]. Biotechnol Bioeng,2004,32(5):698-706.
[44] Bertran M. S., Dale B. E. Enzymatic hydrolysis and recrystallization behavior of initiallyamorphous cellulose [J]. Biotechnol Bioeng,1985,27(2):177-181.
[45] Puri V. P. Effect of crystallinity and degree of polymerization of cellulose on enzymaticsaccharification [J]. Biotechnol Bioeng,1984,26(10):1219-1222.
[46] Quijano G., Couvert A., Amrane A. Ionic liquids: applications and future trends inbioreactor technology [J]. Bioresour Technol,2010,101(23):8923-8930.
[47] Picquet M., Poinsot D., Stutzmann S., et al. Ionic liquids: media for better molecularcatalysis [J]. Toptics Catal,2004,29(3-4):139-143.
[48] Welton T. Room-tmperature ionic liquids-solvents for synthesis and catalysis [J]. ChemRev,1999,99(8):2071-2083.
[49] Yang Z., Pan W. Ionic liquids: green solvents for nonaqueous biocatalysis [J]. EnzymeMicrob Technol,2005,37(1):19-28.
[50] Zhao D., Wu M., Kou Y., et al. Ionic liquids: applications in catalysis [J]. Catal Today,2002,74(1-2):157-189.
[51] Seddon K. R. Ionic liquids for clean technology [J]. J Chem Technol Biotechnol,1997,68(4):351-356.
[52] Rogers R. D., Seddon K. R. Ionic liquids-solvents of the future?[J]. Science,2003,302(5646):792-793.
[53] El Seoud O. A., Koschella A., Fidale L. C., et al. Applications of ionic liquids incarbohydrate chemistry: a window of opportunities [J]. Biomacromolecules,2007,8(9):2629-2647.
[54] Casas A., Oliet M., Alonso M., et al. Dissolution of Pinus radiata and Eucalyptusglobulus woods in ionic liquids under microwave radiation: lignin regeneration andcharacterization [J]. Sep Purif Technol,2012,97(3September):115-122.
[55] Binder J. B., Gray M. J., White J. F., et al. Reactions of lignin model compounds in ionicliquids [J]. Biomass Bioenergy,2009,33(9):1122-1130.
[56] Li W., Sun N., Stoner B., et al. Rapid dissolution of lignocellulosic biomass in ionicliquids using temperatures above the glass transition of lignin [J]. Green Chem,2011,13(8):2038-2047.
[57] Pu Y., Jiang N., Ragauskas A. J. Ionic liquid as a green solvent for lignin [J]. J WoodChem Technol,2007,27(1):23-33.
[58] Lateef H., Grimes S., Kewcharoenwong P., et al. Separation and recovery of celluloseand lignin using ionic liquids: a process for recovery from paper-based waste [J]. J ChemTechnol Biotechnol,2009,84(12):1818-1827.
[59] Swatloski R. P., Spear S. K., Holbrey J. D., et al. Dissolution of cellulose with ionicliquids [J]. JAm Chem Soc,2002,124(18):4974–4975.
[60] Feng L., Chen Z. L. Research progress on dissolution and functional modification ofcellulose in ionic liquids [J]. J Mol Liq,2008,142(1):1-5.
[61] Remsing R. C., Swatloski R. P., Rogers R. D., et al. Mechanism of cellulose dissolutionin the ionic liquid1-n-butyl-3-methylimidazolium chloride: a13C and35/37Cl NMRrelaxation study on model systems [J]. Chem Commun,2006,(12):1271-1273.
[62] Zavrel M., Bross D., Funke M., et al. High-throughput screening for ionic liquidsdissolving (ligno-) cellulose [J]. Bioresour Technol,2009,100(9):2580-2587.
[63] Remsing R. C., Hernandez G., Swatloski R. P., et al. Solvation of carbohydrates in N,N’-dialkylimidazolium ionic liquids: a multinuclear NMR spectroscopy study [J]. J PhysChem B,2008,112(35):11071-11078.
[64] Xu A., Wang J., Wang H. Effects of anionic structure and lithium salts addition on thedissolution of cellulose in1-butyl-3-methylimidazolium-based ionic liquid solventsystems [J]. Green Chem,2010,12(2):268-275.
[65] Cho H. M., Gross A. S., Chu J. W. Dissecting force interactions in cellulosedeconstruction reveals the required solvent versatility for overcoming biomassrecalcitrance [J]. JAm Chem Soc,2011,133(35):14033-14041.
[66] Abe M., Fukaya Y., Ohno H. Extraction of polysaccharides from bran with phosphonateor phosphinate-derived ionic liquids under short mixing time and low temperature [J].Green Chem,2010,12(7):1274-1280.
[67] Zhao H., Baker G. A., Song Z., et al. Designing enzyme-compatible ionic liquids that candissolve carbohydrates [J]. Green Chem,2008,10(6):696-705.
[68] Li Q., He Y. C., Xian M., et al. Improving enzymatic hydrolysis of wheat straw usingionic liquid1-ethyl-3-methyl imidazolium diethyl phosphate pretreatment [J]. BioresourTechnol,2009,100(14):3570-3575.
[69] Sun N., Rahman M., Qin Y., et al. Complete dissolution and partial delignification ofwood in the ionic liquid1-ethyl-3-methylimidazolium acetate [J]. Green Chem,2009,11(5):646-655.
[70] Shill K., Padmanabhan S., Xin Q., et al. Ionic liquid pretreatment of cellulosic biomass:enzymatic hydrolysis and ionic liquid recycle [J]. Biotechnol Bioeng,2011,108(3):511-520.
[71] Dadi A. P., Varanasi S., Schall C. A. Enhancement of cellulose saccharification kineticsusing an ionic liquid pretreatment step [J]. Biotechnol Bioeng,2006,95(5):904-910.
[72] Pinkert A., Marsh K. N., Pang S., et al. Ionic liquids and their interaction with cellulose[J]. Chem Rev,2009,109(12):6712-6728.
[73] Viell J., Marquardt W. Disintegration and dissolution kinetics of wood chips in ionicliquids [J]. Holzforschung,2011,65(4):519-525.
[74] Moniruzzaman M., Ono T. Separation and characterization of cellulose fibers fromcypress wood treated with ionic liquid prior to laccase treatment [J]. Bioresour Technol,2013,127(January):132-137.
[75] Cetinkol O. P., Dibble D. C., Cheng G., et al. Understanding the impact of ionic liquidpretreatment on eucalyptus [J]. Biofuels,2010,1(1):33-46.
[76] Lucas M., Macdonald B. A., Wagner G. L., et al. Ionic liquid pretreatment of poplarwood at room temperature: swelling and incorporation of nanoparticles [J]. ACS ApplMater Inter,2010,2(8):2198-2205.
[77] Lucas M., Wagner G. L., Nishiyama Y., et al. Reversible swelling of the cell wall ofpoplar biomass by ionic liquid at room temperature [J]. Bioresour Technol,2011,102(6):4518-4523.
[78] Bahcegul E., Apaydin S., Haykir N. I., et al. Different ionic liquids favor differentlignocellulosic biomass particle sizes during pretreatment to function efficiently [J].Green Chem,2012,14(7):1896-1903.
[79] Brandt A., Hallett J. P., Leak D. J., et al. The effect of the ionic liquid anion in thepretreatment of pine wood chips [J]. Green Chem,2010,12(4):672-679.
[80] Brandt A., Ray M. J., To T. Q., et al. Ionic liquid pretreatment of lignocellulosic biomasswith ionic liquid-water mixtures [J]. Green Chem,2011,13(9):2489-2499.
[81] Tan S. S. Y., MacFarlane D. R., Upfal J., et al. Extraction of lignin from lignocellulose atatmospheric pressure using alkylbenzenesulfonate ionic liquid [J]. Green Chem,2009,11(3):339-345.
[82] Pinkert A., Goeke D. F., Marsh K. N., et al. Extracting wood lignin without dissolving ordegrading cellulose: investigations on the use of food additive-derived ionic liquids [J].Green Chem,2011,13(11):3124-3136.
[83] Muhammad N., Man Z., Bustam M. A., et al. Dissolution and delignification of bamboobiomass using amino acid-based ionic liquid [J]. Appl Biochem Biotechnol,2011,165(3-4):998-1009.
[84] Kilpel inen I., Xie H., King A., et al. Dissolution of wood in ionic liquids [J]. J AgriFood Chem,2007,55(22):9142-9148.
[85] Guerra A., Gaspar A. R., Contreras S., et al. On the propensity of lignin to associate: asize exclusion chromatography study with lignin derivatives isolated from different plantspecies [J]. Phytochemistry,2007,68(20):2570-2583.
[86] Janesko B. G. Modeling interactions between lignocellulose and ionic liquids usingDFT-D [J]. Phys Chem Chem Phys,2011,13(23):11393-11401.
[87] Zhang H., Wu J., Zhang J., et al.1-Allyl-3-methylimidazolium chloride roomtemperature ionic liquid: a new and powerful nonderivatizing solvent for cellulose [J].Macromolecules,2005,38(20):8272-8277.
[88] Zhao H., Jones C. L., Baker G. A., et al. Regenerating cellulose from ionic liquids for anaccelerated enzymatic hydrolysis [J]. J Biotechnol,2009,139(1):47-54.
[89] Muhammad N., Man Z., Bustam M. A., et al. Investigations of novel nitrile-based ionicliquids as pre-treatment solvent for extraction of lignin from bamboo biomass [J]. J IndEng Chem,2013,19(1):207-214.
[90] Cox B. J., Jia S., Zhang Z. C., et al. Catalytic degradation of lignin model compounds inacidic imidazolium based ionic liquids: hammett acidity and anion effects [J]. PolymDegrad Stab,2011,96(4):426-431.
[91] Cheng G., Kent M. S., He L., et al. Effect of ionic liquid treatment on the structures oflignins in solutions: molecular subunits released from lignin [J]. Langmuir,2012,28(32):11850-11857.
[92] Meng L., Kang S., Zhang X., et al. Comparative characterization of lignins extractedfrom cotton stalk based on complete dissolution in different systems [J]. Indu Eng ChemRes,2012,51(29):9858-9866.
[93] Varanasi P., Singh P., Arora R., et al. Understanding changes in lignin of Panicumvirgatum and Eucalyptus globulus as a function of ionic liquid pretreatment [J].Bioresour Technol,2012,126(December):156-161.
[94] Chundawat S. P. S., Donohoe B. S., da Costa Sousa L., et al. Multi-scale visualizationand characterization of lignocellulosic plant cell wall deconstruction duringthermochemical pretreatment [J]. Energy Environ Sci,2011,4(3):973-984.
[95] Singh S., Simmons B. A., Vogel K. P. Visualization of biomass solubilization andcellulose regeneration during ionic liquid pretreatment of switchgrass [J]. BiotechnolBioeng,2009,104(1):68-75.
[96] Sun L., Li C., Xue Z., et al. Unveiling high-resolution, tissue specific dynamic changesin corn stover during ionic liquid pretreatment [J]. RSCAdv,2013,3(6):2017-2027.
[97] Bose S., Barnes C. A., Petrich J. W. Enhanced stability and activity of cellulase in anionic liquid and the effect of pretreatment on cellulose hydrolysis [J]. Biotechnol Bioeng,2012,109(2):434-43.
[98] Auxenfans T., Buchoux S., Djellab K., et al. Mild pretreatment and enzymaticsaccharification of cellulose with recycled ionic liquids towards one-batch process [J].Carbohydr Polym,2012,90(2):805-813.
[99] Li Q., Jiang X., He Y., et al. Evaluation of the biocompatibile ionic liquid1-methyl-3-methylimidazolium dimethylphosphite pretreatment of corn cob forimproved saccharification [J].Appl Microbiol Biotechnol,2010,87(1):117-126.
[100] Huang Q., Wang Q., Gong Z., et al. Effects of selected ionic liquids on lipid productionby the oleaginous yeast Rhodosporidium toruloides [J]. Bioresour Technol,2013,130(February):339-344.
[101] Fu D., Mazza G. Aqueous ionic liquid pretreatment of straw [J]. Bioresour Technol,2011,102(13):7008-7011.
[102] Zhang Q., Vigier K. D. O., Royer S., et al. Deep eutectic solvents: syntheses, propertiesand applications [J]. Chem Soc Rev,2012,41(21):7108-7146.
[103] Francisco M., van den Bruinhorst A., Kroon M. C. Low-transition-temperature mixtures(LTTMs): a new generation of designer solvents [J]. Angew Chem Int Ed,2013,52(11):3074-3085.
[104] Francisco M., van den Bruinhorst A., Kroon M. C. New natural and renewable lowtransition temperature mixtures (LTTMs): screening as solvents for lignocellulosicbiomass processing [J]. Green Chem,2012,14(8):2153-2157.
[105] Jessop P. G., Heldebrant D. J., Li X., et al. Green chemistry: reversiblenonpolar-to-polar solvent [J]. Nature,2005,436(7054):1102-1102.
[106] Zhang Q. H., Oztekin N. S., Barrault J., et al. Activation of microcrystalline cellulose ina CO2-based switchable system [J]. ChemSusChem,2013,6(4):593-596.
[107] Anugwom I., M ki-Arvela P., Virtanen P., et al. Selective extraction of hemicellulosesfrom spruce using switchable ionic liquids [J]. Carbohydr Polym,2012,87(3):2005-2011.
[108] Petkovic M., Ferguson J. L., Gunaratne H. Q. N., et al. Novel biocompatiblecholinium-based ionic liquids-toxicity and biodegradability [J]. Green Chem,2010,12(4):643-649.
[109] Ebner G., Schiehser S., Potthast A., et al. Side reaction of cellulose with common1-alkyl-3-methylimidazolium-based ionic liquids [J]. Tetrahedron Lett,2008,49(51):7322-7324.
[110] Liu Q. P., Hou X. D., Li N., et al. Ionic liquids from renewable biomaterials: synthesis,characterization and application in the pretreatment of biomass [J]. Green Chem,2012,14(2):304-307.
[111] Hou X. D., Liu Q. P., Smith T. J., et al. Evaluation of toxicity and biodegradability ofcholinium amino acids ionic liquids [J]. PloS ONE,2013,8(3): e59145.
[112] Prasad V., Kale R., Kumar V., et al. Carbohydrate chemistry and room temperature ionicliquids (RTILs): recent trends, opportunities, challenges and future perspectives [J]. CurrOrg Synth,2010,7(5):506-531.
[113] Moriel P., García-Suárez E. J., Martínez M., et al. Synthesis, characterization andcatalytic activity of ionic liquids based on biosources [J]. Tetrahedron Lett,2010,51(37):4877-4881.
[114] Tee r R., Serimaa R., Paakkarl T. Crystallinity of cellulose, as determined by CP/MASNMR and XRD methods [J]. Polym Bull,1987,17(3):231-237.
[115] Segal L., Creely J., Martin A., et al. An empirical method for estimating the degree ofcrystallinity of native cellulose using the X-ray diffractometer [J]. Text Res J,1959,29(10):786.
[116] Bonini C., D'Auria M., Emanuele L., et al. Polyurethanes and polyesters from lignin [J].JAppl Polym Sci,2005,98(3):1451-1456.
[117] Kadla J., Kubo S., Venditti R., et al. Lignin-based carbon fibers for composite fiberapplications [J]. Carbon,2002,40(15):2913-2920.
[118] Varanasi P., Singh P., Auer M., et al. Survey of renewable chemicals produced fromlignocellulosic biomass during ionic liquid pretreatment [J]. Biotechnol Biofuels,2013,6(1):1-14.
[119] Geng X., Henderson W. A. Pretreatment of corn stover by combining ionic liquiddissolution with alkali extraction [J]. Biotechnol Bioeng,2012,109(1):84-91.
[120] Lan W., Liu C. F., Sun R. G. Fractionation of bagasse into cellulose, hemicelluloses, andlignin with iIonic liquid treatment followed by alkaline extraction [J]. J Agri Food Chem,2011,59(16):8691-8701.
[121] Evstigneev E. Specific features of lignin dissolution in aqueous and aqueous-organicmedia [J]. Russ JAppl Chem,2010,83(3):509-513.
[122] Kondo R., Sarkanen K. V. Kinetics of lignin and hemicellulose dissolution during theinitial stage of alkaline pulping [J]. Holzforschung,1984,38(1):31-36.
[123] Wang H., Gurau G., Rogers R. D. Ionic liquid processing of cellulose [J]. Chem SocRev,2012,41(4):1519-1537.
[124] Husson E., Buchoux S., Avondo C., et al. Enzymatic hydrolysis of ionicliquid-pretreated celluloses: contribution of CP-MAS13C NMR and SEM [J]. BioresourTechnol,2011,102(15):7335-7342.
[125] Park S., Baker J. O., Himmel M. E., et al. Research cellulose crystallinity index:measurement techniques and their impact on interpreting cellulase performance [J].Biotechnol Biofuels,2010,3:10.
[126] Nelson M. L., O'Connor R. T. Relation of certain infrared bands to cellulosecrystallinity and crystal latticed type. Part I. spectra of lattice types I, II, III and ofamorphous cellulose [J]. JAppl Polym Sci,1964,8(3):1311-1324.
[127] O'Connor R. T., DuPré E. F., McCall E. R. Infrared spectrophotometric procedure foranalysis of cellulose and modified cellulose [J]. Anal Chem,1957,29(7):998-1005.
[128] Sun R., Sun X. Fractional and structural characterization of hemicelluloses isolated byalkali and alkaline peroxide from barley straw [J]. Carbohydr Polym,2002,49(4):415-423.
[129] Faix O. Classification of lignins from different botanical origins by FT-IR spectroscopy[J]. Holzforschung,1991,45(s1):21-28.
[130] Faix O., Beinhoff O. FTIR spectra of milled wood lignins and lignin polymer models(DHP's) with enhanced resolution obtained by deconvolution [J]. J Wood Chem Technol,1988,8(4):505-522.
[131] Wen J. L., Sun S. L., Xue B. L., et al. Quantitative structures and thermal properties ofbirch lignins after ionic liquid pretreatment [J]. JAgri Food chem,2013,61(3):635-645.
[132] Yang H., Yan R., Chen H., et al. Characteristics of hemicellulose, cellulose and ligninpyrolysis [J]. Fuel,2007,86(12):1781-1788.
[133] Fenner R. A., LePhard J. O. Examination of the thermal decomposition of kraft pinelignin by Fourier transform infrared evolved gas analysis [J]. J Agri Food Chem,1981,29(4):846-849.
[134] Karimi K., Emtiazi G., Taherzadeh M. J. Ethanol production from dilute-acid pretreatedrice straw by simultaneous saccharification and fermentation with Mucor indicus,Rhizopus oryzae, and Saccharomyces cerevisiae [J]. Enzyme Microb Technol,2006,40(1):138-144.
[135] Bohlmann G. M. Process economic considerations for production of ethanol frombiomass feedstocks [J]. Ind Biotechnol,2006,2(1):14-20.
[136] Balat M. Production of bioethanol from lignocellulosic materials via the biochemicalpathway: a review [J]. Energy Convers Manage,2011,52(2):858-875.
[137] Sluiter A., Hames B., Ruiz R., et al. Determination of structural carbohydrates andlignin in biomass [S]. Golden, CO: NREL/TP-510-42618,2008, Laboratory AnalyticalProcedure.
[138] Scalbert A., Monties B., Lallemand J. Y. Ether linkage between phenolic acids andlignin fractions from wheat straw [J]. Phytochemistry,1985,24(6):1359-1362.
[139] Seca A. M., Cavaleiro J. A., Domingues F. M., et al. Structural characterization of thelignin from the nodes and internodes of Arundo donax reed [J]. J Agri Food Chem,2000,48(3):817-824.
[140] Sun S. N., Li M. F., Yuan T. Q., et al. Effect of ionic liquid/organic solvent pretreatmenton the enzymatic hydrolysis of corncob for bioethanol production. Part1: structuralcharacterization of the lignins [J]. Ind Crops Prod,2013,43(May):570-577.
[141] Gould J. M. Characterization of lignin in situ by photoacoustic spectroscopy [J]. PlantPhysiol,1982,70(5):1521-1525.
[142] Wu B., Liu W., Zhang Y., et al. Do we understand the recyclability of ionic liquids?[J].Chem-Eur J,2009,15(8):1804-1810.
[143] Wu H., Mora-Pale M., Miao J., et al. Facile pretreatment of lignocellulosic biomass athigh loadings in room temperature ionic liquids [J]. Biotechnol Bioeng,2011,108(12):2865-2875.
[144] Sun F., Chen H. Enhanced enzymatic hydrolysis of wheat straw by aqueous glycerolpretreatment [J]. Bioresour Technol,2008,99(14):6156-6161.
[145] Pan X., Xie D., Yu R. W., et al. Pretreatment of lodgepole pine killed by mountain pinebeetle using the ethanol organosolv process: fractionation and process optimization [J].Ind Eng Chem Res,2007,46(8):2609-2617.
[146] García-Cubero M. T., González-Benito G., Indacoechea I., et al. Effect of ozonolysispretreatment on enzymatic digestibility of wheat and rye straw [J]. Bioresour Technol,2009,100(4):1608-1613.
[147] Doherty T. V., Mora-Pale M., Foley S. E., et al. Ionic liquid solvent properties aspredictors of lignocellulose pretreatment efficacy [J]. Green Chem,2010,12(11):1967-1975.
[148] Hayashi T. Xyloglucans in the primary cell wall [J]. Annu Revf Plant Biol,1989,40(1):139-168.
[149] Paul M., Long F. H0and related indicator acidity function [J]. Chem Rev,1957,57(1):1-45.
[150] Thomazeau C., Olivier-Bourbigou H., Magna L., et al. Determination of an acidic scalein room temperature ionic liquids [J]. JAm Chem Soc,2003,125(18):5264-5265.
[151] Li W., Zhang Z., Han B., et al. Switching the basicity of ionic liquids by CO2[J]. GreenChem,2008,10(11):1142-1145.
[152] Brunauer S., Emmett P. H., Teller E. Adsorption of gases in multimolecular layers [J]. JAm Chem Soc,1938,60(2):309-319.
[153] Barrett E. P., Joyner L. G., Halenda P. P. The determination of pore volume and areadistributions in porous substances. I. Computations from nitrogen isotherms [J]. J AmChem Soc,1951,73(1):373-380.
[154] Kim J. S., Awano T., Yoshinaga A., et al. Immunolocalization and structural variationsof xylan in differentiating earlywood tracheid cell walls of Cryptomeria japonica [J].Planta,2010,232(4):817-824.
[155] Li C. L., Cheng G., Balan V., et al. Influence of physico-chemical changes on enzymaticdigestibility of ionic liquid and AFEX pretreated corn stover [J]. Bioresour Technol,2011,102(13):6928-6936.
[156] Zhu L., O’Dwyer J. P., Chang V. S., et al. Structural features affecting biomassenzymatic digestibility [J]. Bioresour Technol,2008,99(9):3817-3828.
[157] Torr K. M., Love K. T., etinkol. P., et al. The impact of ionic liquid pretreatment onthe chemistry and enzymatic digestibility of Pinus radiata compression wood [J]. GreenChem,2012,14(3):778-787.
[158] Yoon L. W., Ngoh G. C., May Chua A. S., et al. Comparison of ionic liquid, acid andalkali pretreatments for sugarcane bagasse enzymatic saccharification [J]. J ChemTechnol Biotechnol,2011,86(10):1342-1348.
[159] Cosgrove D. J. Growth of the plant cell wall [J]. Nat Rev Mol Cell Biol,2005,6(11):850-861.
[160] Donaldson L., Hague J., Snell R. Lignin distribution in coppice poplar, linseed andwheat straw [J]. Holzforschung,2001,55(4):379-385.
[161] Fromm J., Rockel B., Lautner S., et al. Lignin distribution in wood cell wallsdetermined by TEM and backscattered SEM techniques [J]. J Struct Biol,2003,143(1):77-84.
[162] Agarwal U. P. Raman imaging to investigate ultrastructure and composition of plant cellwalls: distribution of lignin and cellulose in black spruce wood (Picea mariana)[J].Planta,2006,224(5):1141-1153.
[163] McCartney L., Marcus S. E., Knox J. P. Monoclonal antibodies to plant cell wall xylansand arabinoxylans [J]. J Histochem Cytochem,2005,53(4):543-546.
[164] Gustafsson J., Ciovica L., Peltonen J. The ultrastructure of spruce kraft pulps studied byatomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS)[J].Polymer,2003,44(3):661-670.
[165] Hammett L. P. Reaction rates and indicator acidities [J]. Chem Rev,1935,16(1):67-79.
[166] Vallejos M. E., Zambon M. D., Area M. C., et al. Low liquid–solid ratio (LSR) hotwater pretreatment of sugarcane bagasse [J]. Green Chem,2012,14(7):1982-1989.
[167]聂艳丽,刘永国,李娅,等.甘蔗渣资源利用现状及开发前景[J].林业经济,2007,5:61-63.
[168] Pandey A., Soccol C. R., Nigam P., et al. Biotechnological potential of agro-industrialresidues. I: sugarcane bagasse [J]. Bioresour Technol,2000,74(1):69-80.
[169] Schwanninger M., Rodrigues J., Pereira H., et al. Effects of short-time vibratory ballmilling on the shape of FT-IR spectra of wood and cellulose [J]. Vib Spectrosc,2004,36(1):23-40.
[170] Zhao X. B., Wang L., Liu D. H. Peracetic acid pretreatment of sugarcane bagasse forenzymatic hydrolysis: a continued work [J]. J Chem Technol Biotechnol,2008,83(6):950-956.
[171] Zhang Z., O'Hara I. M., Doherty W. U. S. Pretreatment of sugarcane bagasse byacid-catalysed process in aqueous ionic liquid solutions [J]. Bioresour Technol,2012,120(September):149-156.
[172] Vidal B. C., Jr., Dien B. S., Ting K. C., et al. Influence of feedstock particle size onlignocellulose conversion-a review [J]. Appl Biochem Biotechnol,2011,164(8):1405-1421.
[173] Mosier N., Hendrickson R., Ho N., et al. Optimization of pH controlled liquid hot waterpretreatment of corn stover [J]. Bioresour Technol,2005,96(18):1986-1993.
[174] Fu D., Mazza G. Optimization of processing conditions for the pretreatment of wheatstraw using aqueous ionic liquid [J]. Bioresour Technol,2011,102(17):8003-8010.
[175] Mora-Pale M., Meli L., Doherty T. V., et al. Room temperature ionic liquids asemerging solvents for the pretreatment of lignocellulosic biomass [J]. Biotechnol Bioeng,2011,108(6):1229-1245.
[176] Tadesse H., Luque R. Advances on biomass pretreatment using ionic liquids: anoverview [J]. Energy Environ Sci,2011,4(10):3913-3929.
[2] J rgensen H., Kristensen J. B., Felby C. Enzymatic conversion of lignocellulose intofermentable sugars: challenges and opportunities [J]. Biofuel Bioprod Bior,2007,1(2):119-134.
[3] Chandra R., Bura R., Mabee W., et al. Substrate pretreatment: The key to effectiveenzymatic hydrolysis of lignocellulosics?[A]. Olsson L. Advances in BiochemicalEngineering/Biotechnology [C]. Springer Berlin Heidelberg, Biofuels,2007,108:67-93.
[4] David K., Ragauskas A. J. Switchgrass as an energy crop for biofuel production: a reviewof its ligno-cellulosic chemical properties [J]. Energy Environ Sci,2010,3(9):1182-1190.
[5] Agbor V. B., Cicek N., Sparling R., et al. Biomass pretreatment: fundamentals towardapplication [J]. BiotechnolAdv,2011,29(6):675-685.
[6] Olivier-Bourbigou H., Magna L., Morvan D. Ionic liquids and catalysis: recent progressfrom knowledge to applications [J]. Appl CatalA,2010,373(1):1-56.
[7] Saha B. C. Hemicellulose bioconversion [J]. J Ind Microbiol Biotechnol,2003,30(5):279-291.
[8] Gírio F., Fonseca C., Carvalheiro F., et al. Hemicelluloses for fuel ethanol: a review [J].Bioresour Technol,2010,101(13):4775-4800.
[9]Heinze T., Koschella A., Ebringerova A. Chemical functionalization of xylan: a shortreview [C]. ACS Symposium Series.2004.
[10] Sun S. N., Li M. F., Yuan T. Q., et al. Effect of ionic liquid pretreatment on the structureof hemicelluloses from corncob [J]. JAgri Food Chem,2012,60(44):11120-11127.
[11] Hendriks A., Zeeman G. Pretreatments to enhance the digestibility of lignocellulosicbiomass [J]. Bioresour Technol,2009,100(1):10-18.
[12] Avgerinos G., Wang D. I. C. Selective solvent delignification for fermentationenhancement [J]. Biotechnol Bioeng,1983,25(1):67-83.
[13] Sannigrahi P., Kim D., Jung S., et al. Pseudo-lignin and pretreatment chemistry [J].Energy Environ Sci,2011,4(4):1306–1310.
[14] Langan P., Gnanakaran S., Rector K. D., et al. Exploring new strategies for cellulosicbiofuels production [J]. Energy Environ Sci,2011,4(10):3820-3833.
[15] Lynd L. R., Laser M. S., Bransby D., et al. How biotech can transform biofuels [J].Nature Biotechnol,2008,26(2):169-172.
[16] Hamelinck C. N., Hooijdonk G. v., Faaij A. P. Ethanol from lignocellulosic biomass:techno-economic performance in short-, middle-and long-term [J]. Biomass Bioenerg,2005,28(4):384-410.
[17] Tong X., Ma Y., Li Y. Biomass into chemicals: conversion of sugars to furan derivativesby catalytic processes [J].Appl Catal, A,2010,385(1):1-13.
[18] Alvira P., Tomás-Pejó E., Ballesteros M., et al. Pretreatment technologies for an efficientbioethanol production process based on enzymatic hydrolysis: a review [J]. BioresourTechnol,2010,101(13):4851-4861.
[19] Yang B., Wyman C. E. Pretreatment: the key to unlocking low-cost cellulosic ethanol [J].Biofuels Bioprod Bioref,2008,2(1):26-40.
[20] Zhang Y. H. P., Ding S. Y., Mielenz J. R., et al. Fractionating recalcitrant lignocellulose atmodest reaction conditions [J]. Biotechnol Bioeng,2007,97(2):214-223.
[21] Hsu T., Ladisch R., Tsao G. Alcohol from cellulose [J]. Chem Intermediates,1980,1203(3):315-319.
[22] Zheng Y., Pan Z., Zhang R. Overview of biomass pretreatment for cellulosic ethanolproduction [J]. Int JAgric Biol Eng,2009,2(3):51-68.
[23] Zhao X., Zhang L., Liu D. Biomass recalcitrance. Part I: the chemical compositions andphysical structures affecting the enzymatic hydrolysis of lignocellulose [J]. BiofuelsBioprod Bioref Biofpr,2012,6(4):465-482.
[24] Mansfield S. D., Mooney C., Saddler J. N. Substrate and enzyme characteristics thatlimit cellulose hydrolysis [J]. Biotechnol Progress,1999,15(5):804-816.
[25] Cantarella M., Cantarella L., Gallifuoco A., et al. Comparison of different detoxificationmethods for steam-exploded poplar wood as a substrate for the bioproduction of ethanolin SHF and SSF [J]. Process Biochem,2004,39(11):1533-1542.
[26] Fu D., Mazza G., Tamaki Y. Lignin extraction from straw by ionic liquids and enzymatichydrolysis of the cellulosic residues [J]. JAgri Food Chem,2010,58(5):2915-2922.
[27] Lee S. H., Doherty T. V., Linhardt R. J., et al. Ionic liquid-mediated selective extractionof lignin from wood leading to enhanced enzymatic cellulose hydrolysis [J]. BiotechnolBioeng,2009,102(5):1368-1376.
[28] DeMartini J. D., Pattathil S., Avci U., et al. Application of monoclonal antibodies toinvestigate plant cell wall deconstruction for biofuels production [J]. Energy Environ Sci,2011,4(10):4332-4339.
[29] Yang B., Wyman C. E. BSA treatment to enhance enzymatic hydrolysis of cellulose inlignin containing substrates [J]. Biotechnol Bioeng,2006,94(4):611-617.
[30] S derstr m J., Pilcher L., Galbe M., et al. Two-step steam pretreatment of softwood withSO2impregnation for ethanol production [J]. Appl Biochem Biotechnol,2002,98(1-9):5-21.
[31] Sewalt V. J., Ni W., Blount J. W., et al. Reduced lignin content and altered lignincomposition in transgenic tobacco down-regulated in expression of L-phenylalanineammonia-lyase or cinnamate4-hydroxylase [J]. Plant Physiol,1997,115(1):41-50.
[32] Berlin A., Gilkes N., Kurabi A., et al. Enzymatic hydrolysis of steam-exploded andethanol organosolv-pretreated Douglas Fir by novel and commercial fungal-cellulases[J]. Appl Biochem Biotechnol,2005,121:219–230.
[33] Del Rio L. F., Chandra R. P., Saddler J. N. The effects of increasing swelling and anioniccharges on the enzymatic hydrolysis of organosolv-pretreated softwoods at low enzymeloadings [J]. Biotechnol Bioeng,2011,108(7):1549-1558.
[34] Tu M., Pan X., Saddler J. N. Adsorption of cellulase on cellulolytic enzyme lignin fromlodgepole pine [J]. JAgri Food Chem,2009,57(17):7771-7778.
[35] Kumar L., Arantes V., Chandra R., et al. The lignin present in steam pretreated softwoodbinds enzymes and limits cellulose accessibility [J]. Bioresour Technol,2012,103(1):201-208.
[36] Clark T. A., Mackie K. L. Fermentation inhibitors in wood hydrolysates derived from thesoftwood Pinus radiata [J]. J Chem Technol Biotechnol,1984,34(2):101-110.
[37] Heredia-Olea E., Perez-Carrillo E., Serna-Saldivar S. O. Effects of different acidhydrolyses on the conversion of sweet sorghum bagasse into C5and C6sugars and yeastinhibitors using response surface methodology [J]. Bioresour Technol,2012,119(September):216-223.
[38] Palmqvist E., Hahn-H gerdal B. Fermentation of lignocellulosic hydrolysates. II:inhibitors and mechanisms of inhibition [J]. Bioresour Technol,2000,74(1):25-33.
[39] Varga E., Klinke H. B., Réczey K., et al. High solid simultaneous saccharification andfermentation of wet oxidized corn stover to ethanol [J]. Biotechnol Bioeng,2004,88(5):567-574.
[40] Boussaid A., Esteghlalian A., Gregg D., et al. Steam pretreatment of Douglas-fir woodchips-can conditions for optimum hemicellulose recovery still provide adequate accessfor efficient enzymatic hydrolysis?[J]. Appl Biochem Biotechnol,2000,84(1):693-705.
[41] Brunecky R., Vinzant T. B., Porter S. F., et al. Redistribution of xylan in maize cell wallsduring dilute acid pretreatment [J]. Biotechnol Bioeng,2009,102(6):1537-1543.
[42] Grethlein H. E. The effect of pore size distribution on the rate of enzymatic hydrolysis ofcellulosic substrates [J]. Nature Biotechnol,1985,3(2):155-160.
[43] Tanaka M., Ikesaka M., Matsuno R., et al. Effect of pore size in substrate and diffusion ofenzyme on hydrolysis of cellulosic materials with cellulases [J]. Biotechnol Bioeng,2004,32(5):698-706.
[44] Bertran M. S., Dale B. E. Enzymatic hydrolysis and recrystallization behavior of initiallyamorphous cellulose [J]. Biotechnol Bioeng,1985,27(2):177-181.
[45] Puri V. P. Effect of crystallinity and degree of polymerization of cellulose on enzymaticsaccharification [J]. Biotechnol Bioeng,1984,26(10):1219-1222.
[46] Quijano G., Couvert A., Amrane A. Ionic liquids: applications and future trends inbioreactor technology [J]. Bioresour Technol,2010,101(23):8923-8930.
[47] Picquet M., Poinsot D., Stutzmann S., et al. Ionic liquids: media for better molecularcatalysis [J]. Toptics Catal,2004,29(3-4):139-143.
[48] Welton T. Room-tmperature ionic liquids-solvents for synthesis and catalysis [J]. ChemRev,1999,99(8):2071-2083.
[49] Yang Z., Pan W. Ionic liquids: green solvents for nonaqueous biocatalysis [J]. EnzymeMicrob Technol,2005,37(1):19-28.
[50] Zhao D., Wu M., Kou Y., et al. Ionic liquids: applications in catalysis [J]. Catal Today,2002,74(1-2):157-189.
[51] Seddon K. R. Ionic liquids for clean technology [J]. J Chem Technol Biotechnol,1997,68(4):351-356.
[52] Rogers R. D., Seddon K. R. Ionic liquids-solvents of the future?[J]. Science,2003,302(5646):792-793.
[53] El Seoud O. A., Koschella A., Fidale L. C., et al. Applications of ionic liquids incarbohydrate chemistry: a window of opportunities [J]. Biomacromolecules,2007,8(9):2629-2647.
[54] Casas A., Oliet M., Alonso M., et al. Dissolution of Pinus radiata and Eucalyptusglobulus woods in ionic liquids under microwave radiation: lignin regeneration andcharacterization [J]. Sep Purif Technol,2012,97(3September):115-122.
[55] Binder J. B., Gray M. J., White J. F., et al. Reactions of lignin model compounds in ionicliquids [J]. Biomass Bioenergy,2009,33(9):1122-1130.
[56] Li W., Sun N., Stoner B., et al. Rapid dissolution of lignocellulosic biomass in ionicliquids using temperatures above the glass transition of lignin [J]. Green Chem,2011,13(8):2038-2047.
[57] Pu Y., Jiang N., Ragauskas A. J. Ionic liquid as a green solvent for lignin [J]. J WoodChem Technol,2007,27(1):23-33.
[58] Lateef H., Grimes S., Kewcharoenwong P., et al. Separation and recovery of celluloseand lignin using ionic liquids: a process for recovery from paper-based waste [J]. J ChemTechnol Biotechnol,2009,84(12):1818-1827.
[59] Swatloski R. P., Spear S. K., Holbrey J. D., et al. Dissolution of cellulose with ionicliquids [J]. JAm Chem Soc,2002,124(18):4974–4975.
[60] Feng L., Chen Z. L. Research progress on dissolution and functional modification ofcellulose in ionic liquids [J]. J Mol Liq,2008,142(1):1-5.
[61] Remsing R. C., Swatloski R. P., Rogers R. D., et al. Mechanism of cellulose dissolutionin the ionic liquid1-n-butyl-3-methylimidazolium chloride: a13C and35/37Cl NMRrelaxation study on model systems [J]. Chem Commun,2006,(12):1271-1273.
[62] Zavrel M., Bross D., Funke M., et al. High-throughput screening for ionic liquidsdissolving (ligno-) cellulose [J]. Bioresour Technol,2009,100(9):2580-2587.
[63] Remsing R. C., Hernandez G., Swatloski R. P., et al. Solvation of carbohydrates in N,N’-dialkylimidazolium ionic liquids: a multinuclear NMR spectroscopy study [J]. J PhysChem B,2008,112(35):11071-11078.
[64] Xu A., Wang J., Wang H. Effects of anionic structure and lithium salts addition on thedissolution of cellulose in1-butyl-3-methylimidazolium-based ionic liquid solventsystems [J]. Green Chem,2010,12(2):268-275.
[65] Cho H. M., Gross A. S., Chu J. W. Dissecting force interactions in cellulosedeconstruction reveals the required solvent versatility for overcoming biomassrecalcitrance [J]. JAm Chem Soc,2011,133(35):14033-14041.
[66] Abe M., Fukaya Y., Ohno H. Extraction of polysaccharides from bran with phosphonateor phosphinate-derived ionic liquids under short mixing time and low temperature [J].Green Chem,2010,12(7):1274-1280.
[67] Zhao H., Baker G. A., Song Z., et al. Designing enzyme-compatible ionic liquids that candissolve carbohydrates [J]. Green Chem,2008,10(6):696-705.
[68] Li Q., He Y. C., Xian M., et al. Improving enzymatic hydrolysis of wheat straw usingionic liquid1-ethyl-3-methyl imidazolium diethyl phosphate pretreatment [J]. BioresourTechnol,2009,100(14):3570-3575.
[69] Sun N., Rahman M., Qin Y., et al. Complete dissolution and partial delignification ofwood in the ionic liquid1-ethyl-3-methylimidazolium acetate [J]. Green Chem,2009,11(5):646-655.
[70] Shill K., Padmanabhan S., Xin Q., et al. Ionic liquid pretreatment of cellulosic biomass:enzymatic hydrolysis and ionic liquid recycle [J]. Biotechnol Bioeng,2011,108(3):511-520.
[71] Dadi A. P., Varanasi S., Schall C. A. Enhancement of cellulose saccharification kineticsusing an ionic liquid pretreatment step [J]. Biotechnol Bioeng,2006,95(5):904-910.
[72] Pinkert A., Marsh K. N., Pang S., et al. Ionic liquids and their interaction with cellulose[J]. Chem Rev,2009,109(12):6712-6728.
[73] Viell J., Marquardt W. Disintegration and dissolution kinetics of wood chips in ionicliquids [J]. Holzforschung,2011,65(4):519-525.
[74] Moniruzzaman M., Ono T. Separation and characterization of cellulose fibers fromcypress wood treated with ionic liquid prior to laccase treatment [J]. Bioresour Technol,2013,127(January):132-137.
[75] Cetinkol O. P., Dibble D. C., Cheng G., et al. Understanding the impact of ionic liquidpretreatment on eucalyptus [J]. Biofuels,2010,1(1):33-46.
[76] Lucas M., Macdonald B. A., Wagner G. L., et al. Ionic liquid pretreatment of poplarwood at room temperature: swelling and incorporation of nanoparticles [J]. ACS ApplMater Inter,2010,2(8):2198-2205.
[77] Lucas M., Wagner G. L., Nishiyama Y., et al. Reversible swelling of the cell wall ofpoplar biomass by ionic liquid at room temperature [J]. Bioresour Technol,2011,102(6):4518-4523.
[78] Bahcegul E., Apaydin S., Haykir N. I., et al. Different ionic liquids favor differentlignocellulosic biomass particle sizes during pretreatment to function efficiently [J].Green Chem,2012,14(7):1896-1903.
[79] Brandt A., Hallett J. P., Leak D. J., et al. The effect of the ionic liquid anion in thepretreatment of pine wood chips [J]. Green Chem,2010,12(4):672-679.
[80] Brandt A., Ray M. J., To T. Q., et al. Ionic liquid pretreatment of lignocellulosic biomasswith ionic liquid-water mixtures [J]. Green Chem,2011,13(9):2489-2499.
[81] Tan S. S. Y., MacFarlane D. R., Upfal J., et al. Extraction of lignin from lignocellulose atatmospheric pressure using alkylbenzenesulfonate ionic liquid [J]. Green Chem,2009,11(3):339-345.
[82] Pinkert A., Goeke D. F., Marsh K. N., et al. Extracting wood lignin without dissolving ordegrading cellulose: investigations on the use of food additive-derived ionic liquids [J].Green Chem,2011,13(11):3124-3136.
[83] Muhammad N., Man Z., Bustam M. A., et al. Dissolution and delignification of bamboobiomass using amino acid-based ionic liquid [J]. Appl Biochem Biotechnol,2011,165(3-4):998-1009.
[84] Kilpel inen I., Xie H., King A., et al. Dissolution of wood in ionic liquids [J]. J AgriFood Chem,2007,55(22):9142-9148.
[85] Guerra A., Gaspar A. R., Contreras S., et al. On the propensity of lignin to associate: asize exclusion chromatography study with lignin derivatives isolated from different plantspecies [J]. Phytochemistry,2007,68(20):2570-2583.
[86] Janesko B. G. Modeling interactions between lignocellulose and ionic liquids usingDFT-D [J]. Phys Chem Chem Phys,2011,13(23):11393-11401.
[87] Zhang H., Wu J., Zhang J., et al.1-Allyl-3-methylimidazolium chloride roomtemperature ionic liquid: a new and powerful nonderivatizing solvent for cellulose [J].Macromolecules,2005,38(20):8272-8277.
[88] Zhao H., Jones C. L., Baker G. A., et al. Regenerating cellulose from ionic liquids for anaccelerated enzymatic hydrolysis [J]. J Biotechnol,2009,139(1):47-54.
[89] Muhammad N., Man Z., Bustam M. A., et al. Investigations of novel nitrile-based ionicliquids as pre-treatment solvent for extraction of lignin from bamboo biomass [J]. J IndEng Chem,2013,19(1):207-214.
[90] Cox B. J., Jia S., Zhang Z. C., et al. Catalytic degradation of lignin model compounds inacidic imidazolium based ionic liquids: hammett acidity and anion effects [J]. PolymDegrad Stab,2011,96(4):426-431.
[91] Cheng G., Kent M. S., He L., et al. Effect of ionic liquid treatment on the structures oflignins in solutions: molecular subunits released from lignin [J]. Langmuir,2012,28(32):11850-11857.
[92] Meng L., Kang S., Zhang X., et al. Comparative characterization of lignins extractedfrom cotton stalk based on complete dissolution in different systems [J]. Indu Eng ChemRes,2012,51(29):9858-9866.
[93] Varanasi P., Singh P., Arora R., et al. Understanding changes in lignin of Panicumvirgatum and Eucalyptus globulus as a function of ionic liquid pretreatment [J].Bioresour Technol,2012,126(December):156-161.
[94] Chundawat S. P. S., Donohoe B. S., da Costa Sousa L., et al. Multi-scale visualizationand characterization of lignocellulosic plant cell wall deconstruction duringthermochemical pretreatment [J]. Energy Environ Sci,2011,4(3):973-984.
[95] Singh S., Simmons B. A., Vogel K. P. Visualization of biomass solubilization andcellulose regeneration during ionic liquid pretreatment of switchgrass [J]. BiotechnolBioeng,2009,104(1):68-75.
[96] Sun L., Li C., Xue Z., et al. Unveiling high-resolution, tissue specific dynamic changesin corn stover during ionic liquid pretreatment [J]. RSCAdv,2013,3(6):2017-2027.
[97] Bose S., Barnes C. A., Petrich J. W. Enhanced stability and activity of cellulase in anionic liquid and the effect of pretreatment on cellulose hydrolysis [J]. Biotechnol Bioeng,2012,109(2):434-43.
[98] Auxenfans T., Buchoux S., Djellab K., et al. Mild pretreatment and enzymaticsaccharification of cellulose with recycled ionic liquids towards one-batch process [J].Carbohydr Polym,2012,90(2):805-813.
[99] Li Q., Jiang X., He Y., et al. Evaluation of the biocompatibile ionic liquid1-methyl-3-methylimidazolium dimethylphosphite pretreatment of corn cob forimproved saccharification [J].Appl Microbiol Biotechnol,2010,87(1):117-126.
[100] Huang Q., Wang Q., Gong Z., et al. Effects of selected ionic liquids on lipid productionby the oleaginous yeast Rhodosporidium toruloides [J]. Bioresour Technol,2013,130(February):339-344.
[101] Fu D., Mazza G. Aqueous ionic liquid pretreatment of straw [J]. Bioresour Technol,2011,102(13):7008-7011.
[102] Zhang Q., Vigier K. D. O., Royer S., et al. Deep eutectic solvents: syntheses, propertiesand applications [J]. Chem Soc Rev,2012,41(21):7108-7146.
[103] Francisco M., van den Bruinhorst A., Kroon M. C. Low-transition-temperature mixtures(LTTMs): a new generation of designer solvents [J]. Angew Chem Int Ed,2013,52(11):3074-3085.
[104] Francisco M., van den Bruinhorst A., Kroon M. C. New natural and renewable lowtransition temperature mixtures (LTTMs): screening as solvents for lignocellulosicbiomass processing [J]. Green Chem,2012,14(8):2153-2157.
[105] Jessop P. G., Heldebrant D. J., Li X., et al. Green chemistry: reversiblenonpolar-to-polar solvent [J]. Nature,2005,436(7054):1102-1102.
[106] Zhang Q. H., Oztekin N. S., Barrault J., et al. Activation of microcrystalline cellulose ina CO2-based switchable system [J]. ChemSusChem,2013,6(4):593-596.
[107] Anugwom I., M ki-Arvela P., Virtanen P., et al. Selective extraction of hemicellulosesfrom spruce using switchable ionic liquids [J]. Carbohydr Polym,2012,87(3):2005-2011.
[108] Petkovic M., Ferguson J. L., Gunaratne H. Q. N., et al. Novel biocompatiblecholinium-based ionic liquids-toxicity and biodegradability [J]. Green Chem,2010,12(4):643-649.
[109] Ebner G., Schiehser S., Potthast A., et al. Side reaction of cellulose with common1-alkyl-3-methylimidazolium-based ionic liquids [J]. Tetrahedron Lett,2008,49(51):7322-7324.
[110] Liu Q. P., Hou X. D., Li N., et al. Ionic liquids from renewable biomaterials: synthesis,characterization and application in the pretreatment of biomass [J]. Green Chem,2012,14(2):304-307.
[111] Hou X. D., Liu Q. P., Smith T. J., et al. Evaluation of toxicity and biodegradability ofcholinium amino acids ionic liquids [J]. PloS ONE,2013,8(3): e59145.
[112] Prasad V., Kale R., Kumar V., et al. Carbohydrate chemistry and room temperature ionicliquids (RTILs): recent trends, opportunities, challenges and future perspectives [J]. CurrOrg Synth,2010,7(5):506-531.
[113] Moriel P., García-Suárez E. J., Martínez M., et al. Synthesis, characterization andcatalytic activity of ionic liquids based on biosources [J]. Tetrahedron Lett,2010,51(37):4877-4881.
[114] Tee r R., Serimaa R., Paakkarl T. Crystallinity of cellulose, as determined by CP/MASNMR and XRD methods [J]. Polym Bull,1987,17(3):231-237.
[115] Segal L., Creely J., Martin A., et al. An empirical method for estimating the degree ofcrystallinity of native cellulose using the X-ray diffractometer [J]. Text Res J,1959,29(10):786.
[116] Bonini C., D'Auria M., Emanuele L., et al. Polyurethanes and polyesters from lignin [J].JAppl Polym Sci,2005,98(3):1451-1456.
[117] Kadla J., Kubo S., Venditti R., et al. Lignin-based carbon fibers for composite fiberapplications [J]. Carbon,2002,40(15):2913-2920.
[118] Varanasi P., Singh P., Auer M., et al. Survey of renewable chemicals produced fromlignocellulosic biomass during ionic liquid pretreatment [J]. Biotechnol Biofuels,2013,6(1):1-14.
[119] Geng X., Henderson W. A. Pretreatment of corn stover by combining ionic liquiddissolution with alkali extraction [J]. Biotechnol Bioeng,2012,109(1):84-91.
[120] Lan W., Liu C. F., Sun R. G. Fractionation of bagasse into cellulose, hemicelluloses, andlignin with iIonic liquid treatment followed by alkaline extraction [J]. J Agri Food Chem,2011,59(16):8691-8701.
[121] Evstigneev E. Specific features of lignin dissolution in aqueous and aqueous-organicmedia [J]. Russ JAppl Chem,2010,83(3):509-513.
[122] Kondo R., Sarkanen K. V. Kinetics of lignin and hemicellulose dissolution during theinitial stage of alkaline pulping [J]. Holzforschung,1984,38(1):31-36.
[123] Wang H., Gurau G., Rogers R. D. Ionic liquid processing of cellulose [J]. Chem SocRev,2012,41(4):1519-1537.
[124] Husson E., Buchoux S., Avondo C., et al. Enzymatic hydrolysis of ionicliquid-pretreated celluloses: contribution of CP-MAS13C NMR and SEM [J]. BioresourTechnol,2011,102(15):7335-7342.
[125] Park S., Baker J. O., Himmel M. E., et al. Research cellulose crystallinity index:measurement techniques and their impact on interpreting cellulase performance [J].Biotechnol Biofuels,2010,3:10.
[126] Nelson M. L., O'Connor R. T. Relation of certain infrared bands to cellulosecrystallinity and crystal latticed type. Part I. spectra of lattice types I, II, III and ofamorphous cellulose [J]. JAppl Polym Sci,1964,8(3):1311-1324.
[127] O'Connor R. T., DuPré E. F., McCall E. R. Infrared spectrophotometric procedure foranalysis of cellulose and modified cellulose [J]. Anal Chem,1957,29(7):998-1005.
[128] Sun R., Sun X. Fractional and structural characterization of hemicelluloses isolated byalkali and alkaline peroxide from barley straw [J]. Carbohydr Polym,2002,49(4):415-423.
[129] Faix O. Classification of lignins from different botanical origins by FT-IR spectroscopy[J]. Holzforschung,1991,45(s1):21-28.
[130] Faix O., Beinhoff O. FTIR spectra of milled wood lignins and lignin polymer models(DHP's) with enhanced resolution obtained by deconvolution [J]. J Wood Chem Technol,1988,8(4):505-522.
[131] Wen J. L., Sun S. L., Xue B. L., et al. Quantitative structures and thermal properties ofbirch lignins after ionic liquid pretreatment [J]. JAgri Food chem,2013,61(3):635-645.
[132] Yang H., Yan R., Chen H., et al. Characteristics of hemicellulose, cellulose and ligninpyrolysis [J]. Fuel,2007,86(12):1781-1788.
[133] Fenner R. A., LePhard J. O. Examination of the thermal decomposition of kraft pinelignin by Fourier transform infrared evolved gas analysis [J]. J Agri Food Chem,1981,29(4):846-849.
[134] Karimi K., Emtiazi G., Taherzadeh M. J. Ethanol production from dilute-acid pretreatedrice straw by simultaneous saccharification and fermentation with Mucor indicus,Rhizopus oryzae, and Saccharomyces cerevisiae [J]. Enzyme Microb Technol,2006,40(1):138-144.
[135] Bohlmann G. M. Process economic considerations for production of ethanol frombiomass feedstocks [J]. Ind Biotechnol,2006,2(1):14-20.
[136] Balat M. Production of bioethanol from lignocellulosic materials via the biochemicalpathway: a review [J]. Energy Convers Manage,2011,52(2):858-875.
[137] Sluiter A., Hames B., Ruiz R., et al. Determination of structural carbohydrates andlignin in biomass [S]. Golden, CO: NREL/TP-510-42618,2008, Laboratory AnalyticalProcedure.
[138] Scalbert A., Monties B., Lallemand J. Y. Ether linkage between phenolic acids andlignin fractions from wheat straw [J]. Phytochemistry,1985,24(6):1359-1362.
[139] Seca A. M., Cavaleiro J. A., Domingues F. M., et al. Structural characterization of thelignin from the nodes and internodes of Arundo donax reed [J]. J Agri Food Chem,2000,48(3):817-824.
[140] Sun S. N., Li M. F., Yuan T. Q., et al. Effect of ionic liquid/organic solvent pretreatmenton the enzymatic hydrolysis of corncob for bioethanol production. Part1: structuralcharacterization of the lignins [J]. Ind Crops Prod,2013,43(May):570-577.
[141] Gould J. M. Characterization of lignin in situ by photoacoustic spectroscopy [J]. PlantPhysiol,1982,70(5):1521-1525.
[142] Wu B., Liu W., Zhang Y., et al. Do we understand the recyclability of ionic liquids?[J].Chem-Eur J,2009,15(8):1804-1810.
[143] Wu H., Mora-Pale M., Miao J., et al. Facile pretreatment of lignocellulosic biomass athigh loadings in room temperature ionic liquids [J]. Biotechnol Bioeng,2011,108(12):2865-2875.
[144] Sun F., Chen H. Enhanced enzymatic hydrolysis of wheat straw by aqueous glycerolpretreatment [J]. Bioresour Technol,2008,99(14):6156-6161.
[145] Pan X., Xie D., Yu R. W., et al. Pretreatment of lodgepole pine killed by mountain pinebeetle using the ethanol organosolv process: fractionation and process optimization [J].Ind Eng Chem Res,2007,46(8):2609-2617.
[146] García-Cubero M. T., González-Benito G., Indacoechea I., et al. Effect of ozonolysispretreatment on enzymatic digestibility of wheat and rye straw [J]. Bioresour Technol,2009,100(4):1608-1613.
[147] Doherty T. V., Mora-Pale M., Foley S. E., et al. Ionic liquid solvent properties aspredictors of lignocellulose pretreatment efficacy [J]. Green Chem,2010,12(11):1967-1975.
[148] Hayashi T. Xyloglucans in the primary cell wall [J]. Annu Revf Plant Biol,1989,40(1):139-168.
[149] Paul M., Long F. H0and related indicator acidity function [J]. Chem Rev,1957,57(1):1-45.
[150] Thomazeau C., Olivier-Bourbigou H., Magna L., et al. Determination of an acidic scalein room temperature ionic liquids [J]. JAm Chem Soc,2003,125(18):5264-5265.
[151] Li W., Zhang Z., Han B., et al. Switching the basicity of ionic liquids by CO2[J]. GreenChem,2008,10(11):1142-1145.
[152] Brunauer S., Emmett P. H., Teller E. Adsorption of gases in multimolecular layers [J]. JAm Chem Soc,1938,60(2):309-319.
[153] Barrett E. P., Joyner L. G., Halenda P. P. The determination of pore volume and areadistributions in porous substances. I. Computations from nitrogen isotherms [J]. J AmChem Soc,1951,73(1):373-380.
[154] Kim J. S., Awano T., Yoshinaga A., et al. Immunolocalization and structural variationsof xylan in differentiating earlywood tracheid cell walls of Cryptomeria japonica [J].Planta,2010,232(4):817-824.
[155] Li C. L., Cheng G., Balan V., et al. Influence of physico-chemical changes on enzymaticdigestibility of ionic liquid and AFEX pretreated corn stover [J]. Bioresour Technol,2011,102(13):6928-6936.
[156] Zhu L., O’Dwyer J. P., Chang V. S., et al. Structural features affecting biomassenzymatic digestibility [J]. Bioresour Technol,2008,99(9):3817-3828.
[157] Torr K. M., Love K. T., etinkol. P., et al. The impact of ionic liquid pretreatment onthe chemistry and enzymatic digestibility of Pinus radiata compression wood [J]. GreenChem,2012,14(3):778-787.
[158] Yoon L. W., Ngoh G. C., May Chua A. S., et al. Comparison of ionic liquid, acid andalkali pretreatments for sugarcane bagasse enzymatic saccharification [J]. J ChemTechnol Biotechnol,2011,86(10):1342-1348.
[159] Cosgrove D. J. Growth of the plant cell wall [J]. Nat Rev Mol Cell Biol,2005,6(11):850-861.
[160] Donaldson L., Hague J., Snell R. Lignin distribution in coppice poplar, linseed andwheat straw [J]. Holzforschung,2001,55(4):379-385.
[161] Fromm J., Rockel B., Lautner S., et al. Lignin distribution in wood cell wallsdetermined by TEM and backscattered SEM techniques [J]. J Struct Biol,2003,143(1):77-84.
[162] Agarwal U. P. Raman imaging to investigate ultrastructure and composition of plant cellwalls: distribution of lignin and cellulose in black spruce wood (Picea mariana)[J].Planta,2006,224(5):1141-1153.
[163] McCartney L., Marcus S. E., Knox J. P. Monoclonal antibodies to plant cell wall xylansand arabinoxylans [J]. J Histochem Cytochem,2005,53(4):543-546.
[164] Gustafsson J., Ciovica L., Peltonen J. The ultrastructure of spruce kraft pulps studied byatomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS)[J].Polymer,2003,44(3):661-670.
[165] Hammett L. P. Reaction rates and indicator acidities [J]. Chem Rev,1935,16(1):67-79.
[166] Vallejos M. E., Zambon M. D., Area M. C., et al. Low liquid–solid ratio (LSR) hotwater pretreatment of sugarcane bagasse [J]. Green Chem,2012,14(7):1982-1989.
[167]聂艳丽,刘永国,李娅,等.甘蔗渣资源利用现状及开发前景[J].林业经济,2007,5:61-63.
[168] Pandey A., Soccol C. R., Nigam P., et al. Biotechnological potential of agro-industrialresidues. I: sugarcane bagasse [J]. Bioresour Technol,2000,74(1):69-80.
[169] Schwanninger M., Rodrigues J., Pereira H., et al. Effects of short-time vibratory ballmilling on the shape of FT-IR spectra of wood and cellulose [J]. Vib Spectrosc,2004,36(1):23-40.
[170] Zhao X. B., Wang L., Liu D. H. Peracetic acid pretreatment of sugarcane bagasse forenzymatic hydrolysis: a continued work [J]. J Chem Technol Biotechnol,2008,83(6):950-956.
[171] Zhang Z., O'Hara I. M., Doherty W. U. S. Pretreatment of sugarcane bagasse byacid-catalysed process in aqueous ionic liquid solutions [J]. Bioresour Technol,2012,120(September):149-156.
[172] Vidal B. C., Jr., Dien B. S., Ting K. C., et al. Influence of feedstock particle size onlignocellulose conversion-a review [J]. Appl Biochem Biotechnol,2011,164(8):1405-1421.
[173] Mosier N., Hendrickson R., Ho N., et al. Optimization of pH controlled liquid hot waterpretreatment of corn stover [J]. Bioresour Technol,2005,96(18):1986-1993.
[174] Fu D., Mazza G. Optimization of processing conditions for the pretreatment of wheatstraw using aqueous ionic liquid [J]. Bioresour Technol,2011,102(17):8003-8010.
[175] Mora-Pale M., Meli L., Doherty T. V., et al. Room temperature ionic liquids asemerging solvents for the pretreatment of lignocellulosic biomass [J]. Biotechnol Bioeng,2011,108(6):1229-1245.
[176] Tadesse H., Luque R. Advances on biomass pretreatment using ionic liquids: anoverview [J]. Energy Environ Sci,2011,4(10):3913-3929.