固定化纤维素酶水解玉米秸秆的研究

以壳聚糖小球为载体固定纤维素酶,研究了固定化纤维素酶的酶学性质,并以经过蒸汽爆破预处理的玉米秸秆为底物,研究了固定化酶水解的最优条件.结果表明纤维索酶经过固定化后,其米氏常数为0.42 mg/mL,半衰期为162 h;酶解的最佳条件为固定化酶与底物的质量比为1:2.5、固液比为1:2.4(m/V)、温度为50℃,pH为5.0.秸秆水解率可达33%,纤维素水解率可达70%.     

乙酸甲酯的催化精馏水解实验研究

在自行设计的催化精馏塔中,以Amberlyst 35wet阳离子交换树脂为催化剂,全回流操作下,对乙酸甲酯催化精馏水解进行了研究。考察了空速、塔高度、回流进料比(体积比)以及进料中水酯物质的量比等操作条件对水解反应的影响。实验结果表明,在空速0.09 min-1,催化剂装填高度80 cm,提馏段7块塔板,回流进料比5∶1,进料中水酯物质的量比6.5∶1时,乙酸甲酯水解率达到83.5%。     

Graft copolymerizations of modified cellulose,grafting of acrylonitrile,and methyl methacrylate on carboxy methyl cellulose

Graft copolymers of acrylonitrile (ACN), methyl methacrylate (MMA), and their mixtures on carboxy methyl cellulose (d.S 0.4–0.5) were prepared by the use of ceric ion initiator in aqueous medium. The graft copolymers were characterized by IR spectroscopy. The extent of graft copolymerization of ACN and MMA was measured in terms of graft level, molecular weight of grafted polymer chains, and the frequency of grafting as functions of ceric ion concentration. It was found that at comparable reaction conditions, the molecular weight of the grafted polymer chains and the frequency of grafting were not of the same order of magnitude. For the monomer mixtures, the copolymer compositions obtained from the total nitrogen contents of the copolymer samples showed that a disproportionately low amount of ACN monomeric units were incorporated into the graft copolymer, even at high ACN content of the feed. © 1996 John Wiley & Sons, Inc.     

粗纤维素酶液对微晶纤维素酶解的影响因素

栗生灰黑孔菌多被用于产漆酶的研究,很少有利用其纤维素酶的报道。为了降低在纤维素水解中纤维素酶的使用成本,利用栗生灰黑孔菌发酵制备的粗纤维素酶液,以微晶纤维素为底物模型,研究粗纤维素酶液水解微晶纤维素的最佳pH、温度和最佳表面活性剂助剂种类及浓度,并对不同表面活性剂存在条件下的纤维素酶解动力学、紫外和荧光光谱进行了研究。结果表明,粗纤维素酶水解微晶纤维素的最佳条件为pH 4.8,温度50℃,最佳表面活性剂助剂为吐温80,添加剂量为1.12mg/g底物;吐温80的添加可提高粗纤维素酶解的最大反应速度常数V_max,降低米氏常数K_m;表面活性剂改变了纤维素酶的紫外和荧光最大吸收峰,酰胺Ⅰ带和酰胺Ⅲ带的谱峰,可能通过与纤维素酶中的氨基酸残基发生反应影响了纤维素酶的结构,进而影响了微晶纤维素的水解反应。该研究为进一步降低纤维素水解成本提供了理论指导。     

Alkaline hydrolysis of methyl acrylate grafted cellulose fibers

In this work, methyl acrylate grafted cellulose fibers were hydrolyzed in an aqueous NaOH solution to obtain a superabsorbent hydrogel. The effect of process variables, such as the hydrolysis reaction time, temperature, and NaOH concentration, during alkaline hydrolysis were carefully determined and optimized. The degree of hydrolysis was estimated on the basis of the determination of the carboxylate group contents. The material loss during hydrolysis followed a first‐order reaction mechanism. The differences in the behavior of the grafted fibers during hydrolysis could be explained by their structural differences. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

超声波-微波辅助柠檬酸催化纤维素水解条件

以柠檬酸为催化剂,采用超声波-微波相结合的辅助手法对自制稻草纤维素进行了水解研究。以还原糖得率为指标,在单因素试验的基础上,通过3因素3水平的正交试验考察了酸浓度、超声波处理时间和微波加热时间对指标的影响。对实验结果进行了极差分析和方差分析,结果表明,最佳反应条件为：柠檬酸浓度20%、超声波处理90 min、微波500 W加热30 min,此时还原糖得率最高,达64.46%。对稻草纤维素原料和水解残渣进行了红外表征,结果显示,水解残渣仍以纤维素的形式存在,可重新水解,提高原料利用率。     

Sulfonic acid catalyst based on silica foam supported copolymer for hydrolysis of cellulose

Mesocellular silicon foam supported poly(chloromethylstyrene-co-divinylbenzene) (MCF–copolymer) was synthesized. It has a pore size of 24.2 nm. The pore volume and the surface area were 0.84 cm³/g and 246.9 m²/g, respectively. MCF–copolymer supported sulfonic acid was accomplished via sulfonation with concentrated sulfuric acid. The acid amount on the MCF–copolymer was 2.03 mmol/g. Hydrolysis of banana pseudo-stem fibers and microcrystalline cellulose was carried out over the catalyst. The large pore size favors the diffusion of molecules in catalyzing bulky molecules. The corresponding catalytic turnover frequencies (TOF) were 5.57 h^− 1 and 8.066 h^− 1.     

醋酸甲酯催化精馏水解过程模拟

利用醋酸甲酯水解体系热力学、水解反应动力学以及催化填料的基础数据,采用化工流程模拟与分析的方法,系统地对醋酸甲酯催化精馏水解过程进行了模拟研究。通过与实验数据进行对比,验证了该模拟方法的正确性。通过对工艺条件的灵敏度分析,获得该过程较优的工艺参数。在对现有工艺流程模拟的基础上,结合工业实际操作,提出两种工艺改进方案。     

催化反应精馏在醋酸甲酯水解的工业应用

经过醋酸甲酯水解过程分析,得出利用催化反应精馏方法水解醋酸甲酯是可行的.应用分段组合方法,解决了催化反应精馏过程催化剂装填问题,以及反应与精馏的整合匹配问题,并实现了工业规模应用.工业应用表明:用反应精馏水解醋酸甲酯是成功的,具有醋酸甲酯水解率高(60%～75%)、液体循环量小、蒸汽消耗低、循环冷却水用量小等优点.     

Comparison of catalytic hydrolysis of bagasse cellulose under heterogeneous and homogeneous systems

The conversion of cellulose into valuable chemicals has attracted a great deal of interest. In this study, heterogeneous and homogeneous systems in the conversion of bagasse cellulose into the total reducing sugars were investigated. In the heterogeneous system, the effects of several critical factors including types and concentrations of ionic liquid, temperature, and time were all investigated for cellulosic conversion. Parameters considered included temperature, dosage of catalyst, and water in the homogeneous system. It was found that the hydrolysis capacity for cellulose in homogeneous system was better than that in heterogeneous system. In addition, the structure and physicochemical properties of the treated cellulose were characterized by Fourier transform infrared spectroscopy, thermogravimetry, and scanning electron microscopy, and then compared with the native fibers. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42228.     

Immobilization of cellulase on functionalized cobalt ferrite nanoparticles

Amine functionalized cobalt ferrite (AF-CoFe₂O₄) magnetic nanoparticles (MNPs) were used for immobilization of cellulase enzyme via 1-ethyl-3-[3-dimethylaminopropyl] carbodiimide hydrochloride (EDS) and N-hydroxy-succinimide (NHS) coupling reaction. The structural, morphological and magnetic properties of AF-CoFe₂O₄ were determined. TEM micrograph revealed a mean diameter of ～8 nm and showed that the AF-CoFe₂O₄ remain distinct with no significant change in size after binding with cellulase. Fourier transform infrared (FT-IR) spectroscopy confirmed the binding of cellulase to AF-CoFe₂O₄. The properties of immobilized cellulase were investigated by optimizing binding efficiency, pH, temperature and reusability. The results showed that the immobilized cellulase has higher thermal stability than free cellulase, which might be due to covalent interaction between cellulase and AF-CoFe₂O₄ surface. The immobilized cellulase also showed good reusability after recovery. Therefore, AF-CoFe₂O₄ MNPs can be considered as promising candidate for enzyme immobilization.     

硅基MCF材料固载脂肪酶转化餐饮废油产生物柴油

引言"地沟油"重返餐桌现象日益成为关系民众身体健康、社会和谐发展的焦点,开发合理有效处置方式,挖掘餐饮废油的剩余经济价值,是解决"地沟油"问题的根本出路。长链脂肪酸和低碳醇经过酯化反应后生成的脂肪酸酯,可以替代石油炼制的柴油作为车用燃料[1-2],即生物柴油。研究表明餐     

醋酸甲酯水解催化反应精馏模拟及工业化试验

采用非平衡级速率模型对醋酸甲酯水解过程进行了模拟计算,考察了水酯比、回流进料比等对醋酸甲酯水解率及塔釜醋酸浓度的影响,得到了下一阶段工业化试验的工艺条件,为工业化生产提供了技术支持.并在年产35kt聚乙烯醇(PVA)生产装置中采用新型立体传质塔板(CTST)反应精馏塔板,进行了醋酸甲酯水解反应精馏塔的工业化试验.通过工业化试验,确定了生产的工艺条件:醋酸甲酯进料8m3·h-1,水酯比3.0,回流进料比3.0,转化率达75%左右.并且模拟结果和试验结果吻合较好.     

基于最小二乘法的阳离子交换树脂催化醋酸甲酯水解研究

以001×7(732)强酸性阳离子树脂作为催化剂,用最小二乘法拟合法寻找反应最佳条件,经实验得出优化反应条件为:反应温度50℃,以001×7(732)离子交换树脂作催化剂,树脂用量(g)/反应液体积(L)=0.08~0.32,水解平衡转化率可达77%。     

纤维素酶分子的纤维素吸附区的研究进展

纤维素是生物界中最重要的碳源物质，其生物降解对维持地球上的碳素循环至关重要。其降解涉及到一系列的纤维素酶，是一个多酶协同的过程。近年来相继发现纤维素酶大都含有催化区和可与纤维素结合且氨基酸序列较为保守的功能区，即纤维素吸附区（cellulosebindingdomain,CBD）。通过序列之间的比较，用小角度X射线衍射、核磁共振及流水基簇分析等方法，在CBD的结构、功能及与纤维素的吸附机制等方面有了较深人的了解。本文为近十年来此领域研究进展的简述。     

生物质碳磺酸的制备及其催化水解纤维素性能

对炭化温度、磺化条件以及不同碳源等因素对生物质碳磺酸的酸量、表面结构及催化纤维素水解活性的影响进行了系统研究,并采用XRD、BET、 FT-IR和SEM等对碳磺酸的微观特征进行了分析,发现合适的炭化温度和炭化程度是制备高酸量碳磺酸的关键,在相同的炭化和磺化条件下,用不同生物质碳源制备得到碳磺酸的酸量接近,微观结构不同对纤维素水解催化活性有一定影响。在本文研究的几种碳磺酸中,具有蜂窝大孔结构的竹炭碳磺酸呈现比较突出的催化活性。将竹粉在400℃炭化3 h,然后在180℃下磺化8 h,得到竹炭碳磺酸的总酸量和磺酸量分别可达5.34和1.25 mmol·g^-1。     

催化精馏与固定床联合工艺用于乙酸甲酯水解

在原乙酸甲酯催化精馏水解技术工业化应用成功基础上,为进一步提高乙酸甲酯水解率,利用聚乙烯醇厂已具备的固定床设备,建立了乙酸甲酯水解催化精馏与固定床联合的工艺.通过系统的实验考察了进料位置、水酯比、回流进料比和空速对乙酸甲酯水解率和酸水比的影响,得出了满足厂家要求的适宜工艺条件,并与原催化精馏单塔工艺进行了比较.研究表明...     

New detergent mechanism using cellulase revealed by change in physicochemical properties of cellulose

Sebum in naturally soiled cotton undershirt and oleic acid in artificially soiled cotton cloth, which entered interfiber space in the interior of cotton fibers were easily removed by alkaline cellulase fromBacillus sp., but only with difficulty by commonly used detergent ingredients such as surfactant and protease. Adsorption isotherms and the rate of hydrolysis of alkaline cellulase against insoluble cellulose powders revealed that the lower the relative crystallinity of cellulose powder, the more adsorptive alkaline cellulase became and the more hydrolysis was promoted. With alkaline cellulase, cotton having the highest relative crystallinity was adsorbed at pH 9 and 5°C, liberated a negligible small amount of reducing sugar at pH 9 and 40°C, and produced no changes in the degree of polymerization of cotton cellulose and in the tensile strength of cotton fabric at pH 9 and 30°C. On the other hand, differential scanning calorimetric studies revealed that under similar conditions even a small quantity of alkaline cellulase drastically reduced the amount of water bound to cellulose in cotton. Because water was bound only with hydroxy groups of cellulose molecules in the amorphous region of cotton fibers, it can be understood that soil entering the interfiber space of amorphous interlamellae in the interior of cotton fibers, was easily removed as the hydrated cellulose in the interlamellae was slightly hydrolyzed by alkaline cellulase. A new detergent mechanism is proposed.     

Tailoring the ionic transfer characteristics of polyvinyl chloride-based heterogeneous ion exchange membranes by embedding carboxy methyl cellulose in membrane channels

Polyvinyl chloride-based heterogeneous cation exchange membranes were modified by embedding carboxy methyl cellulose in ionic transfer channels of membrane. The effect of CMC to PVC blend ratios on properties of membranes was studied. SOM images showed uniform distribution and surfaces for prepared membranes relatively. The SEM images showed uniform and dense structure for the membranes. The XRD pattern also demonstrated amorphous structure for the membranes. Membrane water content was improved from 25 to 39 % by increase of CMC concentration up to 32 %wt. Similar trend was found for membrane surface hydrophilicity. The membrane ion exchange capacity, fixed ion concentration, membrane potential, charge density, transport number, permselectivity, and ionic flux were enhanced initially by increase of CMC ratio up to 16 %wt and then began to decrease by increase in CMC concentration from 16 to 32 %wt. The membrane oxidative stability and areal electrical resistance showed decreasing trends by utilizing of carboxy methyl cellulose in the membrane matrix. Membrane transport number and selectivity were also increased by increase of electrolyte concentration. Similar trend was found for the membrane electrical conductivity by increase of electrolyte concentration. Also prepared membranes showed higher transport number, selectivity, and areal electrical resistance at pH 7 compared to other pH values.     

温度敏感的固定化纤维素酶的合成及性能

具有低临界溶解温度（LCST）特性的聚合物聚（N-异丙基丙烯酰胺）与纤维素酶键联，对键联后的酶的各种性能进行了研究。实验结果表明，固定化的纤维素酶仍具有LCST特性，其稳定性也有所提高。