CN101298620 天然纤维素原料经离子液体分级处理一步发酵制备乙醇的方法

本发明涉及利用天然纤维素原料经离子液体分级处理一步发酵制备乙醇的方法。其中将天然纤维素原料依次用离子液体A和B处理分别除去半纤维素、木质素后，再以得到的纤维素为底物一步发酵制备乙醇，所述的离子液体A为酸性或碱性离子液体，所述的离子液体B为卤化咪唑类离子液体。     

南极假丝酵母脂肪酶B在离子液体/超临界流体体系中的稳定性模拟

脂肪酶在离子液体/超临界流体体系中的结构稳定性是影响其活性的重要因素。本文采用分子动力学方法分别研究了南极假丝酵母脂肪酶B(CALB)在离子液体CYPHOS IL-201/极性超临界流体CHF_3两相体系和离子液体CYPHOS IL-201/非极性超临界流体CO_2两相体系中的结构稳定性,揭示影响CALB结构稳定性的因素。研究结果表明,在超临界CHF_3中,CHF_3破坏蛋白维持α螺旋结构的氢键是蛋白结构不稳定的主要原因;在超临界CO_2中,CALB蛋白的结构紧密性降低,有序二级结构发生了变化,导致稳定性下降。离子液体和两种超临界流体均形成了两相体系,蛋白处于离子液体相中,离子液体不溶于超临界流体,但超临界流体部分进入离子液体相,降低了离子液体相的黏度。其中,相比于CYPHOS IL-201/CO_2体系,CYPHOS IL-201/CHF_3体系的黏度降低多。在离子液体CYPHOS IL-201与超临界流体(CHF_3、CO_2)形成的两相体系中,离子液体CYPHOS IL-201具有保护蛋白结构的作用,使CALB蛋白结构更加稳定。     

离子液体双水相体系及其在生物分离中的应用

作为一种高效而温和的新型绿色分离体系,离子液体双水相体系结合了离子液体和双水相体系的优点。因此倍受国内外研究者的青睐。介绍了双水相萃取技术的原理和离子液体双水相体系;综述了离子液体双水相体系在生物分离中的研究进展,主要包括抗生素、蛋白质、和食用色素等的萃取分离;并展望了离子液体双水相体系在生物分离中的应用前景。     

离子液体的应用及前景

离子液体(ionic liquids)是在室温或室温附近完全由离子组成的有机液体物质。它作为一类新型绿色介质,近年来获得了突飞猛进的发展。推动离子液体研究迅速发展的直接动力来源于国际社会对清洁生产、环境保护、循环经济的强烈愿望,以及离子液体本身的探索价值和应用潜力。     

离子液体在生物催化反应中的应用

首先概括了离子液体中生物催化反应的特点;阐述了离子液体在生物催化反应中的应用进展,主要包括:蛋白酶催化的反应、脂肪酶催化的反应、氧化还原酶催化的反应以及其它酶催化的反应.离子液体通常起到了提高酶的活性或稳定性,并提高产物收率和选择性的作用;并展望了离子液体作为溶剂和共溶剂在生物催化反应中的发展前景.     

离子液体在天然活性物质提取中的应用研究进展

查阅近年来国内外相关文献,并进行分析、归纳和总结 , 综述离子液体在天然活性物质提取中的应用研究进展。离子液体作为一 种绿色溶剂,并以其独特性质,近年来在天然活性物质提取领域的应用研究备受关注。不过,目前用于天然活性物质提取的离子液体大 多仅为咪唑类型, 且尚未发现不同类型离子液体对不同种类天然活性成分的提取效率具有明显的特异性和规律性, 这有待进一步深入研究。     

离子液体1-丁基-3-甲基咪唑氯盐对溶菌酶结晶的影响

以亲水性离子液体1-丁基-3-甲基咪唑氯盐(BmimCl)为添加剂,研究离子液体对溶菌酶结晶的影响.分别考察了离子液体对溶菌酶晶体数量与尺寸、晶体形貌及蛋白质纯度的影响,并探讨了离子液体对结晶过程影响的作用机制.离子液体通过增大溶菌酶的溶解度和其自身低蒸气压两种途径,降低了溶菌酶在结晶过程中的过饱和度,更有利于晶体的成核和生长,得到更好的结果.如避免多晶态现象的发生,增大晶体的尺寸,降低溶菌酶样品纯度的要求.X-射线衍射分析表明,离子液体未改变晶体的晶型结构,但可提高晶体的衍射分辨率.     

离子液体1-丁基-3-甲基咪唑氯代盐对溶菌酶结晶的影响

以亲水性离子液体1-丁基-3-甲基咪唑氯盐(BmimCl)为添加剂,研究离子液体对溶菌酶结晶的影响.分别考察了离子液体对溶菌酶晶体数量与尺寸、晶体形貌及蛋白质纯度的影响,并探讨了离子液体对结晶过程影响的作用机制.离子液体通过增大溶菌酶的溶解度和其自身低蒸气压两种途径,降低了溶菌酶在结晶过程中的过饱和度,更有利于晶体的成核和生长,得到更好的结果.如避免多晶态现象的发生,增大晶体的尺寸,降低溶菌酶样品纯度的要求.X-射线衍射分析表明,离子液体未改变晶体的晶型结构,但可提高晶体的衍射分辨率.     

离子液体修饰的SBA-16材料在猪胰脂肪酶固定化中的应用

合成了功能化的甲基咪唑类离子液体,并将功能化离子液体修饰介孔材料SBA-16。以三乙酸甘油酯的水解为探针反应,考察离子液体修饰的SBA-16固定化猪胰脂肪酶(PPL)的酶活、最适反应条件及重复稳定性等酶学性质。结果表明:固定化酶对温度的敏感度降低,酶活力及稳定性均显著提高,比酶活是原粉SBA-16固定化酶的1.75倍,重复使用6次后仍然保持最初活性的57%;与原粉SBA-16固定化酶保留的38%相比,有明显的提高。同时通过N2吸附-脱附、红外光谱和热重等方法分析了离子液体修饰对SBA-16结构的影响,结果发现,离子液体修饰后材料保持了原有的介孔结构,修饰后载体表面性质和结构性质导致了PPL酶学性质的变化。     

模拟水环境离子液体污染对小麦幼苗生长及生理特性的影响

通为了研究离子液体对小麦的毒害, 以周麦18、百农207和百旱207三种小麦为实验材料, 研究了不同质量浓度(0、100、300、500、700 mg·L-1)的离子液体1-乙基-3-甲基咪唑溴化盐对三种小麦幼苗生长及生理特性的影响。结果表明, 随着离子液体浓度的增加, 三种小麦的株高、根长、光合色素、净光合速率和鲜质量都随之降低, 而MDA含量和POD活性则随之增加。在离子液体低浓度100 mg·L-1处理下, 三种小麦相比, 百农207的株高、根长、净光合速率、光合色素含量都没有显著下降, MDA和POD活性也没有显著上升, 表明该品种在此浓度下未引起胁迫响应, 表明其耐逆性高于其他两个品种。当质量浓度为300 mg·L-1—700 mg·L-1时, 三种小麦的各项指标与对照相比都有显著性差异。因此说明离子液体对三种小麦都有一定的毒害作用, 且随着离子液体质量浓度增加毒害作用逐渐增大; 三种小麦对离子液体的耐受性也不同, 相对而言, 百农207抗性最强。     

Enzyme catalysis in ionic liquids

Ionic liquids offer new possibilities for the application of solvent engineering to biocatalytic reactions. Although in many cases ionic liquids have simply been used to replace organic solvents, they have often led to improved process performance. Unlike conventional organic solvents, ionic liquids possess no vapor pressure, are able to dissolve many compounds, and can be used to form two-phase systems with many solvents. To date, reactions involving lipases have benefited most from the use of ionic liquids, but the use of ionic liquids with other enzymes and in whole-cell processes has also been described. In some cases, remarkable results with respect to yield, (enantio)selectivity or enzyme stability were observed.     

Effect of ionic liquid on activity, stability, and structure of enzymes: A review

Ionic liquids have shown their potential as a solvent media for many enzymatic reactions as well as protein preservation, because of their unusual characteristics. It is also observed that change in cation or anion alters the physiochemical properties of the ionic liquids, which in turn influence the enzymatic reactions by altering the structure, activity, enatioselectivity, and stability of the enzymes. Thus, it is utmost need of the researchers to have full understanding of these influences created by ionic liquids before choosing or developing an ionic liquid to serve as solvent media for enzymatic reaction or protein preservation. So, in the present review, we try to shed light on effects of ionic liquids chemistry on structure, stability, and activity of enzymes, which will be helpful for the researchers in various biocatalytic applications.     

Evaluation of parallel milliliter-scale stirred-tank bioreactors for the study of biphasic whole-cell biocatalysis with ionic liquids

As clear structure-activity relationships are still rare for ionic liquids, preliminary experiments are necessary for the process development of biphasic whole-cell processes involving these solvents. To reduce the time investment and the material costs, the process development of such biphasic reaction systems would profit from a small-scale high-throughput platform. Exemplarily, the reduction of 2-octanone to (R)-2-octanol by a recombinant Escherichia coli in a biphasic ionic liquid/water system was studied in a miniaturized stirred-tank bioreactor system allowing the parallel operation of up to 48 reactors at the mL-scale. The results were compared to those obtained in a 20-fold larger stirred-tank reactor. The maximum local energy dissipation was evaluated at the larger scale and compared to the data available for the small-scale reactors, to verify if similar mass transfer could be obtained at both scales. Thereafter, the reaction kinetics and final conversions reached in different reactions setups were analysed. The results were in good agreement between both scales for varying ionic liquids and for ionic liquid volume fractions up to 40%. The parallel bioreactor system can thus be used for the process development of the majority of biphasic reaction systems involving ionic liquids, reducing the time and resource investment during the process development of this type of applications.     

Oxidative enzymes possess catalytic activity in systems with ionic liquids

Oxidative enzymes, laccase C from Trametes sp. and horseradish and soybean peroxidases, catalyzed oxidation reactions in systems with ionic liquids whose content varied from several volume percent to almost total non-aqueous ionic liquids. Similar to the effects produced by standard organic solvents used in non-aqueous enzymology, catalytic activity of the enzymes was decreased by adding a water-miscible ionic liquid, 4-methyl-N-butylpyridinium tetrafluoroborate, or by suspending the enzyme in a water-immiscible ionic liquid, 1-butyl-3-methylimdizaolium hexafluorophosphate. For the oxidation of anthracene, catalyzed by laccase C and assisted by a number of mediators, addition of 4-methyl-N-butylpyridinium tetrafluoroborate, instead of tert-butanol, increased the yield of the oxidation product several-fold.     

Biocatalysis in ionic liquids - advantages beyond green technology

In recent years researchers have started to explore a particular class of organic solvents called room temperature ionic liquids - or simply ionic liquids - to identify their unique advantages for biocatalysis. Because they lack vapour pressure, ionic liquids hold potential as green solvents. Furthermore, unlike organic solvents of comparable polarity, they often do not inactivate enzymes, which simplifies reactions involving polar substrates such as sugars. Biocatalytic reactions in ionic liquids have also shown higher selectivity, faster rates and greater enzyme stability; however, these solvents present other challenges, among them difficulties in purifying ionic liquids and controlling water activity and pH, higher viscosity and problems with product isolation.     

Thorough chemical modification of wood-based lignocellulosic materials in ionic liquids

Homogenous acylation and carbanilation reactions of wood-based lignocellulosic materials have been investigated in ionic liquids. We have found that highly substituted lignocellulosic esters can be obtained under mild conditions (2 h, 70 degrees C) by reacting wood dissolved in ionic liquids with acetyl chloride, benzoyl chloride, and acetic anhydride in the presence of pyridine. In the absence of pyridine, extensive degradation of the wood components was found to occur. Highly substituted carbanilated lignocellulosic material was also obtained in the absence of base in ionic liquid. These chemical modifications were confirmed by infrared spectroscopy, (1)H NMR, and quantitative (31)P NMR of the resulting derivatives. The latter technique permitted the degrees of substitution to be determined, which were found to vary between 81% and 95% for acetylation, benzoylation, and carbanilation, accompanied by similarly high gains in weight percent values. Thermogravimetric measurements showed that the resulting materials exhibit different thermal stabilities from those of the starting wood, while differential scanning calorimetry showed discrete new thermal transitions for these derivatives. Scanning electron microscopy showed the complete absence of fibrous characteristics for these derivatives, but instead, a homogeneous porous, powdery appearance was apparent. A number of our reactions were also carried out in completely recycled ionic liquids, verifying their utility for potential applications beyond the laboratory bench.     

The effects of acetate anion on cellulose dissolution and reaction in imidazolium ionic liquids

Quantum mechanical calculations were carried out to determine the mechanisms for the superiority of the imidazolium acetate-based ionic liquids to the corresponding chloride-based ionic liquids. Our results indicate that the imidazolium cation can react with the acetate anion to generate a carbene, a highly reactive intermediate. The carbene produced then reacts with cellulose to facilitate its dissolution in the ionic liquid solvents in addition to the stronger hydrogen bonds formed between the acetate anion and the hydroxyl groups on cellulose. The mechanisms for the imidazolium cation and acetate anion reactions involve the initial ion pairing of the cation and anion via hydrogen bonding and electrostatic interactions. The hydrogen bond formed between the C2–H on the imidazolium cation and COO⁻ of the anion facilitates the transfer of the H⁺ to the anion to form a carbene intermediate.     

Buffer-mediated activation of Candida antarctica lipase B dissolved in hydroxyl-functionalized ionic liquids

Ionic-liquid buffer having phosphate anion was synthesized for the development of buffered enzymatic ionic liquid systems. Both the conformation and transesterification activity of Candida antarctica lipase B (CALB) dissolved in the hydroxyl-functionalized ionic liquids were buffer dependent. Intrinsic fluorescence studies indicated that the CALB possessed a more compact conformation in the medium consisted of ionic liquid buffer having phosphate anion and hydroxyl-functionalized ionic liquids like 1-(1-hydroxyethyl)-3-methyl-imidazolium tetrafluoroborate and 1-(1-hydroxyethyl)-3-methyl-imidazolium nitrate. High activity and outstanding stability could be obtained with the CALB enzyme in the buffered ionic liquids for the transesterification.     

Biocatalytic transformations in ionic liquids

Room temperature ionic liquids are non-volatile, thermally stable and highly polar; they are also moderately hydrophilic solvents. Here, we discuss their use as reaction media for biocatalysis. Enzymes of widely diverging types are catalytically active in ionic liquids or aqueous biphasic ionic liquid systems. Lipases, in particular, maintain their activity in anhydrous ionic liquid media; the (enantio)selectivity and operational stability are often better than in traditional media. The unconventional solvent properties of ionic liquids have been exploited in biocatalyst recycling and product recovery schemes that are not feasible with traditional solvent systems.     

Enzymatic selective acylation of glycosides in ionic liquids: significantly enhanced reactivity and regioselectivity

The enzymatic selective acylations of carbohydrates in ionic liquids were explored in both organic solvents and ionic liquids to see any significant differences in terms of reactivity and regioselectivity between two different classes of reaction media. Monoprotected glycosides (methyl-6-O-trityl-glucosides and galactosides) were chosen as the substrates with Candida rugosa lipase as an acylation enzyme. Two organic solvents, THF and chloroform, and two ionic liquids, [BMIM]⁺PF₆⁻ ([BMIM]⁺ = 1-butyl-3-methylimidazolium) and [MOEMIM]⁺PF₆⁻ ([MOEMIM]⁺ = 1-methoxyethyl-3-methylimidazolium), were employed as reaction media. The enzymatic reactions were performed in the presence of vinyl acetate at room temperature. It was observed that the reactions in ionic liquids took place more rapidly and more selectively than those in conventional organic solvents.