半纤维素基阿维菌素载药微囊的制备及性能

目前阿维菌素以高效性、无污染和低抗药性等特点而得到广泛应用，但是其稳定性较差，易降解导致使用量较大从而造成浪费。为解决上述问题，本文以半纤维素为基体，利用原位聚合法制备阿维菌素载药微囊（HDCM），通过制备条件、热降解性、储存稳定性和释放动力学研究，确定了HDCM的载药量、热稳定性及释放性能。结果表明，在芯壁比为1∶34（质量比），温度为65℃，pH为3.5的制备条件下，HDCM的载药量可达66.5%，粒径较小且分散均匀。HDCM的热降解性能和恒温热稳定性能较阿维菌素原药有所提高，最高热分解温度从261℃增加到272℃，阿维菌素原药10h后降解率达到12.1%，而载药量为66.5%的HDCM降解率仅为5.2%。HDCM的释放机理满足Fick扩散，阿维菌素原药在水中的累积释放率在12h之内达到83.8%，而HDCM的累积释放率在24h之后才有所增大，12h内其释放率仅为33.7%，表明HDCM具有极好的缓释性能。     

Preparation and Characterization of Hydrophobic Bagasse Hemicellulose-based Films

To improve the hydrophobicity of bagasse hemicellulose-based films, glutaraldehyde was applied when preparing films of original and cationic bagasse hemicellulose with the addition of polyvinyl alcohol and sorbitol. The results showed that the cationic modification could increase the hydrophobicity of the hemicellulose-based film, and the hydrophobicity of hemicellulose-based films crosslinked with glutaraldehyde also increased. However, cationic modification of hemicellulose decreased the stress of the hemicellulose-based film. While crosslinking with glutaraldehyde increased the stress of both the original and cationic hemicellulose-based films. Macrophotography indicated that the film formability of the original hemicellulose was better than that of cationic hemicellulose. Through SEM observation, the degree of bonding of different components of the films was found to be increased due to crosslinking with glutaraldehyde. The crosslinking reaction between glutaraldehyde and hemicellulose was further confirmed by FT-IR spectroscopy.     

Kinetic modeling of hemicellulose hydrolysis in the presence of homogeneous and heterogeneous catalysts

Kinetic models were developed for the hydrolysis of O‐acetyl‐galactoglucomannan (GGM), a hemicellulose appearing in coniferous trees. Homogeneous and heterogeneous acid catalysts hydrolyze GGM at about 90°C to the monomeric sugars galactose, glucose, and mannose. In the presence of homogeneous catalysts, such as HCl, H₂SO₄, oxalic acid, and trifluoroacetic acid, the hydrolysis process shows a regular kinetic behavior, while a prominent autocatalytic effect was observed in the presence of heterogeneous cation‐exchange catalysts, Amberlyst 15 and Smopex 101. The kinetic models proposed were based on the reactivities of the nonhydrolyzed sugar units and the increase of the rate constant (for heterogeneous catalysts) as the reaction progresses and the degree of polymerization decreases. General kinetic models were derived and special cases of them were considered in detail, by deriving analytical solutions for product distributions. The kinetic parameters, describing the autocatalytic effect were determined by nonlinear regression analysis. The kinetic model described very well the overall kinetics, as well as the product distribution in the hydrolysis of water soluble GGM by homogeneous and heterogeneous catalysts. The modelling principles developed in the work can be in principle applied to hydrolysis of similar hemicelluloses as well as starch and cellulose. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1066–1077, 2014     

纳滤技术在粘胶纤维生产中的应用

阐述了粘胶生产中分离废碱中半纤维素的必要性。重点介绍了纳滤技术的优点及其在分离中的应用。粘胶纤维生产车间采用的凯能科氏膜和沈阳新华膜的使用经验,对2种膜系统的工艺参数进行了详细对比,提出实际应用中出现的问题及解决办法。     

生物质水解制备糠醛的研究进展

生物质中的碳水化合物是当今世界最重要的可再生资源,将这部分资源转化为附加值较高的化工产品以代替日趋枯竭的化石资源,势必成为绿色化学发展的重点。典型生物质中半纤维素的含量高达30%,经催化水解为五碳糖后再进一步脱水可得到重要的平台化合物糠醛。综述了生物质催化水解制备糠醛的研究进展并对未来的研究趋势进行了展望。     

Starting to Gel: How Arabidopsis Seed Coat Epidermal Cells Produce Specialized Secondary Cell Walls

For more than a decade, the Arabidopsis seed coat epidermis (SCE) has been used as a model system to study the synthesis, secretion and modification of cell wall polysaccharides, particularly pectin. Our detailed re-evaluation of available biochemical data highlights that Arabidopsis seed mucilage is more than just pectin. Typical secondary wall polymers such as xylans and heteromannans are also present in mucilage. Despite their low abundance, these components appear to play essential roles in controlling mucilage properties, and should be further investigated. We also provide a comprehensive community resource by re-assessing the mucilage phenotypes of almost 20 mutants using the same conditions. We conduct an in-depth functional evaluation of all the SCE genes described in the literature and propose a revised model for mucilage production. Further investigation of SCE cells will improve our understanding of plant cell walls.     

香蕉茎秆酶法脱胶工艺及其脱胶纤维性能

为了将生物质废弃物香蕉茎秆进行高值化利用,采用酶法脱胶工艺制备香蕉茎秆纤维。研究超声预处理工艺中频率、处理温度对香蕉茎秆脱胶率的影响,确定较佳的超声预处理工艺。将预处理后的香蕉茎秆粗纤维进行半纤维素酶、果胶酶脱胶,分别考察缓冲液pH、酶浓度、反应温度对脱胶率的影响。结果表明:预处理工艺中超声处理的较佳频率为40 kHz,温度为70℃;酶法脱胶工艺中较佳的半纤维素酶缓冲液pH为5.5,半纤维素酶浓度为0.004 g·ml^-1,反应温度为50℃;较佳的果胶酶缓冲液pH为6.0,果胶酶浓度为0.003 g·ml^-1,反应温度为55℃。采用傅里叶红外光谱(FTIR)、X射线衍射(XRD)和扫描电镜(SEM)分析酶法较佳工艺制备的香蕉茎秆纤维的理化特性;并对其机械性能进行测试与分析。FTIR及XRD结果表明:酶法较佳工艺制备的香蕉茎秆纤维去除了半纤维素和大部分果胶,相对结晶度为66.4%;机械性能测试结果表明酶法较佳工艺制备的香蕉茎秆纤维的拉伸强度、杨氏模量和断裂伸长率分别是118.48 MPa,15.15 GPa,0.67%。     

半纤维素吸水树脂的合成及在水泥砂浆中的应用初探

首次以粘胶纤维制备过程中产生的半纤维素碱液为原料,利用自由基聚合方法,制备了一种环保可降解半纤维素吸水树脂,并对其进行了结构表征.通过考察单体、引发剂用量对树脂吸水率的影响,确定最适宜反应条件.用合成的吸水树脂掺入水泥砂浆后制样,测其力学性能,结果表明,加入适量研制的树脂可大大提高水泥砂浆成型后的抗压强度.     

树脂吸附-超滤协同分离甘蔗渣碱法半纤维素

针对碱法提取半纤维素中木质素含量高、纯化难的问题,通过疏水树脂吸附-超滤协同处理,探讨纯化分离方式的影响。利用离子色谱（IC）、紫外分光光度计（UV）、凝胶渗透色谱（GPC）和热重量分析（TGA）,对半纤维素的化学组分、分子量、热稳定性等特性进行了分析。结果表明,树脂吸附-膜超滤处理能有效脱除木质素,获得较高分子量的半纤维素,分子主链结构没有发现明显变化,热稳定性略有提高。经树脂吸附后的半纤维素侧链单元有较为明显的变化,分子量较小的半纤维素带有更多侧链木质素单元,通过苯基糖苷键（PhGlc）与碳水化合物相连,可通过树脂吸附-超滤协同处理分离出来,从而达到分离不同侧链结构的半纤维素。