Structural Changes of Wheat Straw Lignin during Formic Acid Treatment

The aromatic nature of lignin makes it a potential renewable source of chemicals and other valuable products.Isolation of lignin from lignocellulosic biomass using organic solvents enables the production of high-purity lignin.The use of formic acid in the organosolv pulping and fractionation process has been widely studied.Characterization of lignin is necessary to achieve valueadded applications of lignin.To simplify the isolation of formic acid-treated lignin,herein,milled wheat straw lignin(MWSL) was employed as an archetype for characterization of the structural changes of lignin during formic acid treatment.The results showed that the MWSL was GSH-type(comprising p-hydroxyphenyl(H),guaiacyl(G),and syringyl(S) monolignols) and underwent structural changes during formic acid treatment.Lignin was esterified during the formic acid treatment.The content of alkyl hydroxyl groups in lignin decreased upon formic acid treatment,corresponding to an increase of the number of double bond equivalents(DBE).Lignin units with active reaction sites were liable to slight condensation,which resulted in a moderate increase of the molecular weight.The molecular weight distribution of formic acid-treated MWSL(FMWSL) was wider than that of the MWSL,although the molecular weight of both species did not differ significantly.The β-O-4 linkage in lignin was partially cleaved during formic acid treatment,resulting in the production of new phenolic structures.This improved the solubility of lignin in the cooking liquor and its reactivity for downstream applications.

THE LIGNIN CONTENT IN BLACK LIQUID OF STRAW AS-AQ BY ULTRAVIOLET SPECTROPHOTOMETER

The measurement of lignin content in black liquid of straw AS-AQ by ultraviolet spectrophotometer(UV) is discussed in this paper. Different dilution multiple and contrast solutions have an effect on the measured results of the lignin content by UV. The calculation method for the absorption coefficient and the scanning spectrum property of liquor acidified by SO2 are introduced in this paper.

A field experimental study of lignin sand stabilizing material(LSSM) extracted from spent-liquor of straw pulping paper mills

A new technique was introduced for sand stabilization and re-vegetation by use of lignin sand stabilizing material(LSSM). LSSM is a reconstructed organic compound with lignin as the most dominant component from the extracts of black-liquor issued by straw pulp paper mills. Unlike the polyvinyl acetate or foamed asphalt commonly used for dune stabilization, the new material is plant-friendly and can be used with virescence actions simultaneously. The field experimental study was conducted since 2001 in China's Northwest Ningxia Hui Autonomous Region and has been proved that LSSM is effective in stabilizing the fugitive dunes, making the arenaceous plants survive and the bare dune vegetative. The advisable solution concentration is 2% and the optimal field spraying quantity is 2 5 L/m^2 The soil nutrients of the stabilized and greened dune, such as organic matter, available phosphorous and total nitrogen are all increased compared with the control treatment, which is certainly helpful to the growth of arenaceous plants. The technique is worthwhile to be popularized because it is provided not only a new method for desertification control but also an outlet for cleaning contaminants issued from the straw paper mills.

POLYETHER POLYURETHANE FROM MODIFIED WHEAT STRAW OXYGEN-ALKALINE LIGNIN

Polyether polyurethane was synthesized from modified wheat straw oxygen-alkaline lignin, polyethylene glycol and two different diisocyanates (diphenylemethane-4, 4’-diisocyanate, tolulene diisocyanate) by solution casting method, its properties were investigated. The results show that modified wheat straw oxygen-alkaline lignin can substitute part of polyethylene glycol to react with diisocyanate to synthesize polyurethane. The molar ratio of NCO to OH and modified wheat straw oxygen-alkaline lignin content affect the properties of lignin-based polyether polyurethane respectively. The addition of plasticizer in the polyurethane synthesis process improves the properties of synthesized polyurethane, especially the elasticity of polyurethane. The synthesized polyurethane from modified wheat straw oxygen-alkali lignin can be used as both engineering plastic and hard foam plastic in future.

WHEAT STRAW ALKALINE LIGNIN AND ITS DERIVATIVES AS RETENTION AID

In this paper, a new type of retention system of PEO/cofactor retention system is introduced, the cofactors used are phenol-formaldehyde resin, wheat straw alkaline lignin and its derivatives such as hydroxymethylated lignin, sulfited lignin and lignin-based phenol-formaldehyde resin. The first pass retention of newsprint slurry and the properties of handsheet are improved by using the system. The results indicate that a new application field for lignin has been exploited.

CHARACTERISTICS OF LIGNIN REACTIONS IN SODA COOKING OF WHEAT STRAW PART 1 REACTION OF UNCONDENSED LIGNIN

Characteristics of uncondensed lignin reactions in soda cooking of wheat straw were studied. Mild and intense cooking conditions were used to get the pulp sample in which lignin was dissolved physically and the pulp sample in which lignin was dissolved chemically respectively. The pulp samples were analyzed by phenolic group determination, alkaline nitrobenzene oxidation and ozonation method. The results indicated that around 90% of lignin in wheat straw is alkali-soluble at the mild conditions, is basically dissolved physically without chemical change. The phenolic group content was not changed greatly, the nitrobenzene oxidation yield only changed slightly during the mild cooking. The phenolic group content was increased obviously and uncondensed lignin content was decreased very much when the intense cooking conditions were applied and the delignification was over 90%. The lignin structure was changed greatly during this period.

麦秆及其制浆废弃物的组分分离与结构特性表征

麦秆资源作为中国产量丰富的秸秆资源,可采用生物化学转化方法制备高价值的可发酵性和功能性糖。研究采用亚氯酸钠漂白法和磨木木质素提取法从麦秆及其制浆废弃物(麦糠)中分离获得高纯度的纤维素、半纤维素和木质素,并对其各组分结构特征及理化特性进行全面解析。结果表明,麦秆和麦糠中的纤维素主要由聚集态的葡聚糖组成,而半纤维素主要成分质量分数分别为82.6%木聚糖、5.3%阿拉伯聚糖、1.5%半乳聚糖和79.3%木聚糖、7.6%阿拉伯聚糖、2.0%半乳聚糖。麦秆和麦糠中的木质素中同时含有3种苯丙烷结构单元:紫丁香基单元、愈创木基单元和对羟基苯基单元,且结构单元之间的连接键主要由β-O-4,β-β和β-5所组成。麦秆和麦糠中的木质素的羟基含量和羧基含量也存在差异,总量分别为5.68,0.11 mmol/g和5.98,0.14 mmol/g。

ON THE BLACK LIQUOR AND RECYCLE COOKING OF AS-AQ STRAW PULP

Thick black liquor, thin black liquor and solid state sodium hydroxide are added to the liquor treated by sulfur dioxide, then the blended liquor is used to recycle cooking of straw pulp. The black liquor, separated liquor and pulp of every cycles are analyzed respectively. Result shows that the content of lignin and organism in recycle black liquor and separated liquor increases faster in the first three cycles and then continues to increase slowly till four or five times, after that it trends to a stable state. The main organism separated from waste liquor of AS-AQ treated by sulfur dioxide is alkali-lignin, above 50% of total lignin in black liquor. The yield of pulp made from recycle cooking is steady, the hardness of pulp has a great improvement with recycle cooking. The brightness of pulp reduces correspondingly before bleaching, and after bleaching the brightness of pulp is relatively high and steady at the same sodium hypo chlorite dosage.

Thermal, Morphological and Cytotoxicity Characterization of Hardwood Lignins Isolated by <i>In-Situ</i>Sodium Hydroxide-Sodium Bisulfate Method

In the present work, lignin is isolated from three different agro-industrial waste, sweet sorghum, rice straw and sugarcane bagasse using in-situ sodium hydroxide-sodium bisulfate methodology. Characterization was performed using fourier transform infrared analysis (FTIR), scan electron microscopy (SEM), thermo gravimetric analysis (TGA). The SEM micrographs showed sponge-like structure except for sugarcane bagasse lignin reveals rock-like structure. The FTIR indicates the presence of hydroxyl, carbonyl and methoxyl groups in the lignin structure. TGA thermograms were relatively same and sugarcane bagasse lignin was found the most thermally stable up to 201˚C as compared to both of soda and kraft sugarcane bagasse lignin and its maximal temperature degradation rate DTGmax was found at 494˚C while 450˚C, 464˚C in addition to thermal stabilities up to 173˚C and 180˚C for sweet sorghum and rice straw lignins respectively. All lignins exhibited low percentage of bio-char less than 10% remained unvalotilized at the end of the thermogravimetric analysis at 800˚C in nitrogen atmosphere, revealing a high conversion yield into volatiles. Moreover, all lignin samples depicted higher cytotoxic potential towards lung cancer cell line (A549), IC50: 12 - 17 μg/ml. These findings suggest that the in-situ separated lignins would be good candidates for pyrolysis, polymer composites preparations and seem to be promising natural anti-cancer agents despite its main utilization as the caner drug delivery substrates.

农作物秸秆饲料化技术研究

秸秆经过适当加工可以转化为高价值的饲料,不仅能有效节约成本,减少环境污染,还能促进资源的循环利用。然而,秸秆中的纤维素和木质素含量较高,在一定程度上限制了其在畜牧业中的应用。综述秸秆饲料化利用的重要性,探讨当前秸秆饲料化处理的主要方法,以期为提升秸秆饲料化的营养价值和利用率提供参考。

秸秆饲料化过程中木质素生物降解的研究进展

我国秸秆资源丰富但饲料化占比低,秸秆木质纤维素尤其是其中的木质素难以被动物体消化利用是影响秸秆饲料化进程的关键制约因素之一。生物降解木质素提升秸秆的营养价值是一种绿色、经济、可用于生产的促进秸秆饲料化方式。本文综述了秸秆木质素的化学成分及作用、木质素降解微生物及相关降解酶、木质素的生物发酵降解相关研究以及在动物养殖中的应用,以期为秸秆饲料化生产提供参考。

油菜秸秆木质素高效降解菌的筛选、鉴定及降解效果研究

试验旨在研究油菜秸秆木质素高效降解菌的筛选、鉴定及降解效果。从油菜秸秆的还田土壤中筛选得到一株木质素高效降解菌株MS25,鉴定其为青霉属真菌(Penicillium)。基于单因素试验及响应面试验方法,对MS25菌株进行产酶特性探究及条件优化,并检验木质素降解能力。结果表明:菌株最佳产漆酶(Lac)时间为5 d,产过氧化物酶(Lip)和锰过氧化物酶(MnP)时间为7 d,最佳温度为50℃,摇床转速为140 r/min,碳氮比为15,产MnP的最适pH值为5,产Lip和Lac最适pH值为6。优化后最佳产酶条件为温度50.22℃、碳氮比12.29、pH值6.21、该条件下Lip、MnP、Lac的活性分别为1984.89、774.87、291.74 U/L,较优化前分别提高33.97%、33.28%、40.35%。最优条件下,秸秆、菌糠中木质素降解率分别为44.67%、43.29%。研究表明,菌株MS25可有效降解木质素,可作为油菜秸秆发酵的优质微生物,并可应用于饲料生产领域。

提高玉米秸秆饲料化品质的食用菌筛选

为改善玉米秸秆加工制备的粗饲料其营养价值低且适口性差等问题,提高玉米秸秆饲料品质,本研究基于ITS条形码进行分类学鉴定的8株食用菌(S1~S8),以玉米秸秆为唯一碳源进行生物发酵培养,通过秸秆中木质纤维素的降解率、粗脂肪和粗蛋白质含量等比对筛选适合于玉米秸秆饲料化的菌株。研究结果表明:S4糙皮侧耳(Pleurotus ostreatus)降解纤维素和木质素的能力最强,达到47.31%和71.39%。S1斑玉蕈(Hypsizygus marmoreus)对半纤维素的降解能力最好,为61.91%。S2肺形侧耳(Pleurotus pulmonarius)粗蛋白质含量提高效果最好,达145%,饲料占比达12.48%。S1斑玉蕈粗脂肪含量提升效果最好,达495%,饲料占比达8.57%。

微生物关键种影响植物残体还田条件下木质素酚浓度——基于30年长期有机培肥试验

探究不同植物残体还田条件下微生物关键种如何影响木质素酚的浓度(木质素酚与土壤有机碳的比值),旨在为不同有机物料还田培肥土壤提供理论和技术依据。本研究以河西绿洲灌区的灌漠土作为研究对象,开展了30 a以施加绿肥(GM)、小麦秸秆(SW)、氮肥(N)、绿肥配施氮肥(GMN)、小麦秸秆配施氮肥(SWN)以及不施肥(CK) 6种不同施肥处理的培肥试验。结果表明:GM和SW处理的土壤有机碳含量显著高于其他处理;有小麦秸秆参与还田的处理显著提高了总木质素酚浓度以及3种木质素酚类单体的浓度,其中总木质素酚浓度在SW处理中分别比CK、GM、N、GMN和SWN处理高了109%、122%、115%、164%和57%;对比不施肥和施化肥处理,植物残体还田显著提高了微生物关键种F3(盘菌纲,Pezizomycetes)、F26(被孢霉菌纲,Mortierellomycetes)、F173(粪壳菌纲,Sordariomycetes)、B74(阿尔法变形菌纲,Alphaproteobacteria)和B87(放线菌纲,Actinobacteria)的相对丰度。本研究共鉴定出15个关键种,其中关键种B831(属阿尔法变形菌纲)与木质素酚浓度呈显著的正相关关系,并且在SW处理下显著富集。本研究为农业生态系统不同培肥方式下微生物关键种如何影响植物衍生的木质素酚提供了科学参考,为深入了解植物残体还田对土壤有机碳周转的影响提供了理论依据。

卡拉胶/秸秆木质素复合膜的制备与性能研究

为提高秸秆的利用价值,利用碱法提取稻草秸秆中的木质素(Straw lignin,SL)与卡拉胶、山梨醇共混,制备出一系列不同SL含量的卡拉胶与秸秆木质素复合膜(C/L复合膜)。通过对膜的结构表征和性能测试,研究SL添加量对复合膜结构和各项性能的影响。结果表明,SL能够有效增强膜的力学性能,改善膜的阻湿性能,增大膜的雾度,并赋予膜抗氧化性和紫外屏蔽性能,但对膜的热稳定性影响不大。在SL含量高于8%时,复合膜拥有均匀和致密的结构,证明SL与复合模之间的相容性良好,红外结果表明,氢键是其主要的键合力;SL添加量为10%时,复合膜可以阻挡绝大部分光紫外线;当SL添加量为12%时,膜的力学性能最佳,拉伸强度为22.97 MPa,断裂伸长率为30.40%;而在SL添加量达到14%时,膜的阻湿性能最优,其水蒸气透过率达到最低值6.78×10^(-11) g/(m·s·Pa),水接触角从28°增大到79°;膜的抗氧化性会随着SL添加量的增大而增大;在添加16%的SL时,复合膜的DPPH(1,1-二苯基-2-三硝基苯肼)自由基清除率由0增加到23.39%。

一株多功能秸秆木质素降解菌株的筛选、鉴定及条件优化

为实现秸秆资源化利用及提高作物产量,本研究从秸秆中筛选木质素降解菌株,并探究其多种功能,发掘微生物资源的目标。通过菌株苯胺蓝筛选培养、木质素酶活力、IAA能力测定及平板对峙试验等探究菌株促腐、促生及抗病潜能;结合形态学、生理生化特征和16S rRNA序列分析对菌株种属进行鉴定;采用秸秆摇瓶及水稻促生试验测定菌株的实际促腐促生功效;设置单因素试验探究菌株发酵的最适条件。分离筛选的功能菌M15H2鉴定为植生拉乌尔菌(Raoultella planticola)。结果显示,该菌株木质素过氧化物酶活可达129.49 U·mL^(-1),锰过氧化物酶可达23.91U·mL^(-1),漆酶酶活可达8.91 U·mL^(-1)。与对照相比,施用M15H2菌液55 d后秸秆腐解率较对照处理提高32.59%;M15H2产IAA量为3.90 mg·L^(-1),水稻植株发芽率、芽长、根长较对照处理分别增长5.67%、31%和40%;菌液M15H2具有一定的抗水稻条斑病效果,抑菌圈直径与菌落直径的比值为1.20。菌株M15H2发酵的最佳p H为5.0,温度为28~32℃,碳源和氮源分别为蔗糖和酵母粉,装液量是50 mL/250 mL。所筛选的菌株M15H2是兼具促生、抗病作用的多功能秸秆促腐菌,能够加速秸秆降解,促进植株健康生长,具有广泛的开发利用前景。

白腐真菌预处理农作物秸秆的研究进展

农作物秸秆资源丰富,对反刍动物来说是一种低成本的可再生粗饲料来源,但秸秆在饲喂动物时其高含量的木质纤维素限制了反刍动物瘤胃微生物的作用,以致不能被有效利用,在实际生产中缺乏理想的处理方式,没有开发出其应有的营养价值。白腐真菌预处理可以提高农作物秸秆的消化率,该菌能够在营养价值相对较低的秸秆上生长,可以通过分泌1种或多种木质纤维素降解酶以及自由基等,将木质纤维素分解为能够被反刍动物消化的糖类等小分子化合物。本文就农作物秸秆的饲料化应用现状、处理方式展开讨论,并对白腐真菌处理木质纤维素的作用机制和影响因素以及在动物生产上的应用进行了综述,旨在为提高农作物秸秆的营养价值提供理论参考。

改性TiO_(2)-太阳光协同强化秸秆产糖的研究

为了强化生物质能源的清洁利用,提高生物质糖转化率,合成了L-缬氨酸改性二氧化钛复合催化剂;随后以稻草秸秆为原料,木质素去除率与还原糖产量为目标,通过改性二氧化钛-太阳光协同预处理强化秸秆酶解糖化效率。过程中考察了催化剂种类、浓度、pH、太阳光光照时间以及光照方式对秸秆还原糖转化率的影响。在单因素试验基础上,对工艺参数进行了正交试验优化。SEM与FT-IR分析结果显示,L-缬氨酸成功负载于二氧化钛颗粒上;形成的复合催化剂联合太阳光辐照可有效强化秸秆还原糖转化率。综合考虑经济性因素,最终方案选择催化剂浓度为35 mg/L、pH为6.0、预处理时间70 min。验证试验显示,木质素去除率可达93.1%。预处理后,酶解糖化过程采用光暗交替循环方案,酶载量20 FPU/g,其还原糖转化率可达117.3 mg/g,还原糖转化率非常显著。

不同土著菌及其复合菌对玉米秸秆降解的影响

为研究一种高效的玉米秸秆降解复合菌,选取了木质素降解优势土著菌密黏褶菌、环状芽孢杆菌、铜绿假单胞菌、栗褐链霉菌、黄孢原毛平革菌、杂色云芝、绿色木霉、黑曲霉,对各单一菌种对玉米秸秆的降解能力进行了测定,通过菌种间的拮抗试验,将单一菌种进行组合,初步构建了一组木质纤维素降解复合菌。结果表明:在整个35 d的预处理周期中,黑曲霉、绿色木霉对秸秆中纤维素、半纤维素体现了较高的降解能力,黑曲霉、绿色木霉对半纤维素的降解率分别为47.81%、37.53%,对纤维素的降解率分别为38.96%、46.32%;黄孢原毛平革菌、杂色云芝对玉米秸秆中的木质素体现了较强的降解能力,对木质素的降解率分别为43.56%、39.17%;菌种拮抗试验表明该试验所选用的真菌、放线菌及细菌之间无拮抗反应,可以进行混合培养;对复合菌预处理前后的玉米秸秆微观结构进行扫描电镜分析,发现在降解过程中复合菌对木质纤维素的结构产生了破坏作用,提高了木质纤维素的可及性;木质素、纤维素、半纤维素的含量在整个发酵过程中都在逐渐减少,发酵结束时复合菌对半纤维素的降解率最高达到48.53%,纤维素的降解率为36.38%,木质素的降解率为40.11%,在提高木质素降解率的同时减少了纤维素消耗。该研究为秸秆类生物质降解及利用提供了参考依据。

秸秆、木质素及其生物炭对潮土CO_2释放及有机碳含量的影响

研究添加秸秆、木质素及其生物炭后潮土CO2释放特征及土壤有机碳含量变化,为合理利用有机物料提供科学依据。采用室内模拟试验,等碳量(1%秸秆/土壤质量比)施入4种物料(秸秆、木质素及其裂解的两种生物炭),分析不同处理土壤CO2释放速率、累积释放量和有机碳、水溶性有机碳(DOC)、易氧化有机碳(ROC)及微生物量碳(MBC)含量的变化与相关性。结果发现,土壤中添加不同物料对土壤CO2释放和有机碳含量有显著影响,秸秆和木质素能提高土壤CO2释放速率、累积释放量及有机碳矿化强度,均达到极显著差异,但两种生物炭处理与对照相比没有显著差异。在培养前期(30 d),不同物料均显著提高了土壤有机碳含量;但培养一年后,仅两种生物炭处理土壤有机碳含量较高,秸秆及木质素与对照相比没有显著差异。秸秆和木质素能显著增加DOC、ROC和MBC等土壤活性有机碳含量,而两种生物炭与对照相比没有明显差异;土壤DOC、ROC(167 mmol·L-1KMn O4)、ROC(33mmol·L-1KMn O4)和MBC直接影响CO2累积释放量,ROC(333 mmol·L-1KMn O4)对CO2累积释放量具有较强的间接作用。相对于秸秆和木质素而言,生物炭增加土壤有机碳含量,而没有增加CO2释放量,因此生物炭农用在固碳减排方面更具有积极意义。