β-O-4型木质素模型化合物的合成及其在GIF型仿酶降解体系中的变化(Ⅱ)

深入研究β-O-4型木质素模型化合物——愈创木基丙三醇-β-愈创木基醚的合成新路线，并利用红外光谱和核磁共振谱对其化学结构进行了分析。采用由Cu^2 吡啶／过氧化氢组成的GIF(GIF-sur-YVETTE)型仿酶体系对这一木质素模型物进行了仿酶降解的研究，并采用GC-MS、^13C NMR等方法分析了该β-O-4型木质素模型化合物在降解过程中的结构变化，在此基础上对这种仿酶降解的机理进行了探讨。研究结果表明：利用溴化铜对4-乙酰基愈创木酚进行溴化后很容易得到4-(α-溴化乙酰基)-愈创木酚中间体，从而提高了合成愈创木基丙三醇-β-愈创木基醚的效率。GIF仿酶降解体系对β-O-4型木质素模型物有较强的碎解能力，降解后产生一系列含羟基、醛基和羧基的芳香族低分子化合物，根据反应产物的结构可以说明β-O-4型木质素模型化合物的主要降解途径为：β-O-4醚键断裂、Cα-Cβ键断裂、Cβ-Cγ键断裂。本研究为该仿酶降解体系在无污染漂白工业上的应用提供理论依据。     

玉米秸秆蒸汽爆破降解产物的分析

采用高效液相色谱(HPLC)和气质联用(GC-MS)色谱技术对玉米秸秆蒸汽爆破降解产物进行分析.玉米秸秆经蒸汽爆破预处理后,其纤维素、半纤维素和木质素降解损失分别为9.60%、47.98%和17.55%.采用HPLC对碳水化合物降解和分解产物定量分析,100g玉米秸秆预处理后,产生甲酸2.10g、乙酸2.00g、乙酰丙酸0.10g、5-羟甲基糠醛0.08g和糠醛0.13g.采用GC-MS对木质素和提取物降解产物定性分析,共检测出14种芳香类化合物、22种脂肪酸类化合物和5种呋喃化合物.     

衍生还原裂解法研究木质素类药物的结构

采用衍生还原裂解法(DFRC)对木质素类药物进行降解,并且采用GC-MS分析裂解产物的组成和结构.结果显示:木质素类药物降解产物中包含有4类化合物,即2,6-二叔丁基-4-甲基苯酚(BHT),单糖,有机酸和相关木质素单元.在1#药物和2#药物中上述4种化合物分别为:12.696％、17.456％、17.989％和51.859％;8.736％、2.991％、44.812％和43.461％.根据所得到的木质素类药物降解产物的生物活性,推测木质素类药物的药效作用可能是由于木质素类药物在人体内能分解为BHT、阿魏酸和甘油单元结构所致.在1#药物和2#药物中,可能在人体内转化为阿魏酸的化合物总量分别为12.572％和5.613％;含有甘油单元的化合物总量分别为6.322％和25.430％.     

利用紫外光谱等研究蒸爆过程中毛竹木质素基本化学结构的变化

运用硝基苯氧化法、紫外光谱法研究了蒸煮爆破过程中毛竹木质素分子一些基本化学结构的降解特征。结果显示5年生毛竹材木质素及磨木木质素的硝基苯氧化产物产量分别为368和325 mmoL.(200g lignin)-1。压力2.0 MPa、时间5 min的蒸煮爆破条件能够导致木质素非缩合型结构较强烈的降解,有助于低分子苯酚类的形成。蒸爆未造成木质素分子重要组成部分的对-香豆酸和阿魏酸等显著的解离,但产生了一定程度的木质素-多糖复合物的降解或芳香环侧链结构的变化。     

红平菇木质素降解酶系统漆酶、锰过氧化物酶及木质素过氧化物酶的检测

木材白腐菌在分解木质素的过程中会产生非特异性的分解木质素结构的酶系统,这些酶系统主要包括细胞外过氧化物酶[锰过氧化物酶(manganese peroxidase,MnP)、木质素过氧化物酶(lignin peroxidase,LiP)]和细胞外酚氧化酶[漆酶(laccase)].因此,在生物修复方面,白腐菌能够有效地降解废水和土壤中难被降解的多氯联苯、多环芳烃、DDT、染料、炸药和其他氯化物、叠氮化合物等.     

漆酶介体体系处理纤维素乙醇木质素的~1H-NMR和~(13)C-NMR表征

针对漆酶处理纤维素乙醇木质素复杂的作用机理,采用~1H-NMR和~(13)C-NMR表征反应过程中木质素的结构变化。研究发现,纤维素乙醇木质素经漆酶处理后,侧链氧化脱除反应使木质素甲氧基含量、β-β型结构减少,β-O-4型结构中部分醚键断裂且漆酶介体体系可促进β-O-4型结构的降解。     

木质素降解产物对纤维素酶和木聚糖酶水解的抑制

在稀酸等化学预处理过程中,木质素会降解生成酚类等产物进入后续糖化阶段,研究表明这些木质素降解产物会抑制木质纤维降解酶的水解效率,然而其抑制机制尚不清楚。笔者选择了3种典型的木质素降解产物:香草醛、4-羟基苯甲醛和丁香醛,考察了它们对商品纤维素酶和木聚糖酶,以及单一关键纤维素酶组分和β-木糖苷酶水解的影响,并探讨其抑制规律。实验结果表明,这3种木质素降解产物对纤维素酶和木聚糖酶的水解均有抑制,其抑制能力随降解产物浓度的增加而增强。当3种木质素降解产物的质量浓度为10 mg/m L时,纤维素酶水解微晶纤维素48 h的葡萄糖得率由71.17%分别减少到33.80%、29.52%和32.03%,说明这3种木质素降解产物对纤维素酶的抑制作用差异不明显。3种木质素降解产物对β-葡萄糖苷酶水解纤维二糖的效率没有影响,但是会强烈抑制外切葡聚糖酶CBH I的酶活。当木质素降解产物的质量浓度为2 mg/m L时,与未添加木质素降解产物的酶活相比,CBH I酶活分别降低至79.64%、86.76%和71.89%,抑制强弱顺序为:丁香醛香草醛4-羟基苯甲醛。此外,3种木质素降解产物对木聚糖酶和β-木糖苷酶的抑制强弱顺序均为:4-羟基苯甲醛香草醛丁香醛,当3种木质素降解产物的质量浓度为10 mg/m L时,木聚糖酶水解木聚糖48 h的木糖得率由57.28%分别减少到12.26%、20.16%和30.43%。抑制动力学试验表明,4-羟基苯甲醛对CBH I的抑制属于竞争性抑制,对β-木糖苷酶的抑制属于非竞争性抑制。     

Trametes trogii WT-1降解欧美杨107杨木质素的初步研究

通过对受毛栓菌侵染的欧美杨107杨木块木质素含量的测定,结合扫描电镜(SEM)观察和红外光谱(IR)分析方法,对WT-1降解欧美杨107杨木块的过程进行初步研究。结果表明:受WT-1的侵染,杨木块木质素含量降低,其木质素降解过程呈现出慢-快-慢的规律;SEM观察结果表明,WT-1对杨木块木质素的降解由胞腔向胞间层进行,其中射线和薄壁组织最先降解,木纤维及导管次之;IR分析表明,受WT-1的侵染杨木块木质素结构发生了变化,木质素芳香核之间通过碳-碳键(—C—C—)连接的空间网状结构被破坏,木质素苯环间的羰基、CH2结构、紫丁香基和愈疮木基等侧链部分被降解,苯环骨架变化明显。     

过氧化氢预处理强化木质纤维原料酶水解研究进展

在木质纤维素的生物降解和转化过程中,木质纤维素的复杂结构和木质素组分限制了碳水化合物的高效酶水解。过氧化氢预处理可以通过破坏木质纤维素的物理化学结构并氧化降解部分木质素,从而改善原料的酶水解效率。过氧化氢预处理主要有过氧化氢-酸、过氧化氢-碱、活化过氧化氢这3类预处理方法。笔者主要归纳了不同预处理过程中的木质素降解机理,总结了过氧化氢预处理强化木质纤维原料酶水解的效果,探讨了预处理对木质纤维原料降解产物的影响,评价了各类过氧化氢预处理的可行性和优缺点。最后,根据过氧化氢预处理的特点分析了过氧化氢预处理的研究策略,展望了过氧化氢预处理的发展趋势。从安全性和经济可行性的角度来看,低试剂用量、低温和低压的预处理条件是未来过氧化氢预处理的主要研究方向。     

-胡萝卜素降解反应研究进展

较系统地总结了近年来有关β-胡萝卜素降解反应方面的研究进展。β-胡萝卜素的主要降解方式包括高温氧化降解、热裂解、化学氧化降解、光氧化降解、生物氧化及酶催化氧化降解等,主要产物种类包括碳数为2以上30以下的醛、酮、醇、羧酸及其酯类等沸点较低的含氧有机化合物,其降解机制依据降解方式各不相同。β-胡萝卜素的降解产物对于制备香精和香料具有重要价值。     

Sulfuric acid bleaching of kraft pulp III: reactivity of kraft pulping-resistant structures under acidic conditions

To investigate the bleaching mechanism, a lignincarbohydrate complex (LCC) model compound, a vinyl ether-type lignin model dimer, and a hexeneuronic acid model compound were treated with dilute sulfuric acid of different pHs. Beech kraft pulp and red pine kraft pulp were also treated with dilute sulfuric acid and then extracted with aqueous alkali. The amount of hexeneuronic acid degradation products in acid effluents and lignin dissolved in alkali effluents were determined. It was found that the benzyl ether-type LCC bond and the vinyl ether bond in lignin were effectively cleaved under the pH where sulfuric acid bleaching of kraft pulp was effective. Hexeneuronic acid group was also effectively degraded during sulfuric acid bleaching. In beech kraft pulp bleaching, both lignin removal and hexeneuronic acid removal contributed to the kappa number reduction. In red pine bleaching, the contribution of hexeneuronic acid removal was negligible, and most of the kappa number reduction was achieved by the lignin removal.Part of this report was presented at the 9th International Symposium on Wood and Pulping Chemistry, Montreal, July 1997     

FTIR-PAS study of light-induced changes in the surface of acetylated or polyethylene glycol-impregnated wood

The objective of this study was to characterize the surface changes in acetylated and polyethylene glycol (PEG)-impregnated wood caused during light irradiation by Fourier transformed infrared photoacoustic spectroscopy analysis to determine their effects on the reduction of light deterioration. Light irradiation made the color of the chemically modified wood lighter or more vivid, whereas it deepened the color of the untreated wood. The color difference during light irradiation was less in the chemically modified wood than the untreated wood. The color difference of PEG-impregnated wood increased with increasing irradiation time. The light irradiation generated much carbonyl and significantly degraded lignin in the untreated wood. The generation of carbonyl and lignin degradation diminished in the acetylated wood in comparison with the untreated wood, indicating that acetylation restrained the photochemical degradation of wood. Deacetylation did not occur during light irradiation of the acetylated wood. The PEG impregnation decreased the generation of carbonyl and degradation of lignin during light irradiation. However, the irradiation occurred a little photochemical degradation of PEG, generating the carbonyl. Therefore, longer light irradiation should increase the degradation of PEG, thus reducing the effect of treatment. The correlation between the color difference and lignin degradation was high, indicating that the color changes during light irradiation significantly depended on lignin degradation. The chemical modification reduced the degradation of lignin and consequently decreased the color difference. Some of the compounds containing the carbonyl generated during light irradiation were water-soluble.This paper was presented at the 50th Annual Meeting of the Japan Wood Research Society, Kyoto, April 2000     

白腐菌在木质纤维素降解中的应用进展

木质素由于具有各种生物学稳定的复杂键型而不易被微生物降解,进而阻碍了纤维素的降解利用,而纤维素是重要的能源性物质,同时又是纸浆的主要成分,因此有效利用木质纤维素的关键是木质素的去除。本文总结白腐菌在生物制浆、乙醇制备的预处理、堆肥和饲料的制备方面的应用,概括提高白腐菌利用效率的方法,并对使用白腐菌处理木质纤维素材料进行展望。     

木粉及其组分的多元醇酸催化热化学液化

分别将木粉、纤维素和木质素在乙二醇中进行热化学液化。研究结果表明木粉中纤维素的非结晶区、木质素和半纤维素首先被液化,而纤维素的结晶区较慢被液化,到液化反应中期基本降解完全,液化产率高于97%。利用在线红外光谱仪跟踪检测了整个液化反应过程,结合GC-MS结果发现:乙二醇在反应过程中脱水生成了二甘醇和三甘醇。在液化反应中,纤维素的糖苷键断裂后生成葡萄糖苷结构,随后葡萄糖苷中的吡喃环也被打开,生成的活性中间体相互反应或与乙二醇反应生成了如3-(2-甲基-[1,3]-二氧戊环-2-基)-丙酸乙酯、乙酰丙酸丁酯等酯类;木质素的苯丙烷结构主要降解为苯酚、2,6-甲氧基苯酚等芳香族衍生物,因此木粉液化产物是聚醚/酯混合多元醇。     

漆酶在生物造纸中的应用

利用生物酶（如漆酶）预处理可以降低化学浆的残余木素量,减少制浆中的能源消耗,提高纸浆强度特性和光泽度等。在介体参与下,漆酶能够降解木素,使残余木素的摩尔质量减少、木素中的酚羟基减少、羰基和羧基增加,对后续的漂白过程起到活化木素的作用。漆酶等酶活系统能将漂白废水中的有机氯化物转变成无机氯和CO2,破坏发色基团组织和结构,降低漂白废水中的TOCl、BOD、COD和色度。漆酶在氧气和介体存在下能使木素产生自由基的缩合,提高纤维间的粘合性,改善高木素含量和纸浆的性能。漆酶作为一种非专一型聚酚酶,在一定程度上可与树脂反应,可以催化好氧污染物的酚羟基基固,生成苯氧自由基和水。     

下的降解

对木质素磺酸盐在紫外光/双氧水(UV/H2O2)体系下的降解过程进行了研究,通过对比处理前后木质素磺酸盐溶液的紫外可见光谱、凝胶渗透色谱(GPC)谱图、红外光谱谱图、1H NMR谱图及溶液化学耗氧量(COD)的变化对其降解过程进行了跟踪和讨论。此外,通过对木质素的模型化合物——愈创木酚降解的研究,推测了降解中苯环的开环过程。实验结果表明,木质素磺酸盐在UV/H2O2体系处理下能够发生降解,降解过程中首先生成一些中间产物,随着反应时间的加长,最终能够降解成CO2、H2O等小分子化合物。     

蒸汽爆破-乙醇蒸煮两步法预处理对麦秆结构的影响

对麦秆采用先蒸汽爆破后乙醇蒸煮的两步法进行预处理,研究预处理对麦秆组分及结构变化的影响。蒸汽爆破过程实验条件选取200 g绝干麦秆,压力1.75 MPa和时间3.5 min。乙醇预处理过程选取80 g蒸汽爆破麦秆(绝干),55%乙醇,两者固液比1∶5(g∶mL),温度170℃、时间30 min。通过高效液相色谱法测定,预处理最终产物组分中半纤维素降低89%左右,木质素降低35%左右。采用红外光谱、纤维形态分布分析及SEM分析对预处理过程中麦秆结构变化情况进行研究,结果表明:蒸汽爆破过程破坏了半纤维素酯键连接且半纤维素降解非常明显,但对纤维素链结构影响和降解作用相对较低;麦秆经过蒸汽爆破预处理后,纤维平均长度明显降低,而平均宽度却显著增加;再经乙醇预处理后纤维平均长度基本保持不变,但平均宽度降低;经两步预处理后麦秆纤维的天然物理结构由紧密到蓬松,纤维束呈松散状态且纤维表面基本无碎片附着物,利于后续加工利用。     

Sulfuric acid bleaching of kraft pulp II: Behavior of lignin and carbohydrate during sulfuric acid bleaching

The purpose of this study was to investigate the behavior of lignin and carbohydrates in kraft pulps during sulfuric acid bleaching. Beech kraft pulp and red pine kraft pulp were bleached with dilute sulfuric acid at pH 1.3 with addition of sodium nitrate and sodium nitrite at 100°C for 1 h. The pulps were then extracted with aqueous sodium hydroxide solution at 70°C for 1 h. Lignin and carbohydrates in the acid effluents and the alkali effluents were analyzed. The carbohydrate compositions of unbleached and bleached kraft pulps were also determined. The residual lignin in kraft pulp was degraded to a molecular size similar to that of milled wood lignin during sulfuric acid bleaching without additives, and it was further degraded to a much smaller molecular size during sulfuric acid bleaching with additives. It was found that the amount of carbohydrate dissolved in the bleach effluents were only about 1 of the dry weight of the kraft pulp under these bleaching conditions. The carbohydrates dissolved during bleaching were mostly of hemicellulose origin.Part of this report was presented at the 8th International Symposium on Wood and Pulping Chemistry, Helsinki, July 1995     

Analysis of progress of oxidation reaction during oxygen-alkali treatment of lignin 2: significance of oxidation reaction of lignin during oxygen delignification

The progress of lignin oxidation during oxygenalkali bleaching of pulp was evaluated by the method based on the difference between permanganate consumption of original pulp and that of the mixture of pulp and effluent after oxygen-alkali bleaching. By low-consistency oxygen bleaching of softwood kraft pulp, the permanganate consumption decreased very little. When the kappa number of the pulp was halved (from 25.4 to 13.4), the decrease in permanganate consumption of 1 g pulp was only 1.22ml of 0.02mol/l potassium permanganate. This value was smaller than that obtained for the oxygen-alkali treatment of a corresponding amount of isolated residual lignin, 6.40ml. This was not due to the slow oxidation of lignin in pulp but to the formation of permanganate-consuming substances from carbohydrates. Those newly formed substances cannot be oxidized by oxygen-alkali treatment. Taking these facts into account, lignin originally present in pulp was found to be oxidized well. Reduction of carbonyl groups in carbohydrates prevented the formation of such substances.Part of this paper was presented at the 10th ISWPC, Yokohama, June 1999; and at the 43rd Lignin Symposium, Fuchu, October 1998