木质纤维素预处理技术研究现状与展望

木质纤维素是自然界中最丰富的可再生资源,可用于生产燃料乙醇、生物柴油等能源产品,也是制备化学品和造纸的主要原料。木质纤维素主要由纤维素、半纤维素和木质素组成,复杂的化学结构限制了其高效利用,故必须对其进行预处理,去除木质素、半纤维素等不可溶物质,从而使其更易被酶水解成可发酵的糖,进而提高木质纤维素的降解转化率。预处理技术可以改变木质纤维原料的内部结构和表面性质,为后续的酶解糖化创造良好条件。从物理、化学、生物、联合处理等4个方面全面综述了不同木质纤维素预处理技术的研究现状,总结了其预处理效果和优缺点,并展望了其未来的研究方向,旨在为木质纤维素生物质降解利用研究提供参考。     

微生物降解木质素的研究进展

木质纤维是地球上最丰富的可再生生物质资源,其三大成分之一的纤维素是生产生物基材料、生物燃料及生物基化学品的重要原料,但是木质素复杂的化学结构阻碍了木质纤维的应用。常规木质素的物理、化学及物理-化学等降解方法常需要高温、高压条件,并且易产生抑制物、造成高能耗和环境污染等问题。微生物介导的生物催化过程通常在温和条件下进行,可以降低能源投入,为木质素的利用提供了更具体、更有效的选择。传统生物降解以白腐菌等真菌为代表,存在预处理周期长、对环境适应性差等问题,而细菌繁殖迅速、环境适应能力强、易于基因操作,成为未来木质素降解菌株的潜在候选者。本文在介绍木质素化学结构的基础上,综述了近年来微生物降解木质素的研究进展,着重分析了降解木质素的微生物(真菌和细菌)、木质素降解酶(过氧化物酶和漆酶)和降解机制,以及微生物降解木质素在脂类、生物塑料、香兰素、废水处理中的应用,并对微生物降解木质素的未来发展进行了展望。     

白腐菌降解木质纤维素顺序规律的研究

通过纤维素、半纤维素和木质素三者含量变化的测定,以及傅立叶变换红外光谱(FTIR)的谱图分析,研究了 BP2、CD1和 AX3三株白腐菌在50 天培养期中降解木屑基质中木质纤维素的规律。结果表明,三株白腐菌对木屑基质中纤维素、半纤维素和木质素三者的降解具有一定的顺序和选择性,即先降解半纤维素和木质素,再同时降解半纤维素、纤维素和木质素;从降解比例来看,三株菌对木质素具有很强的降解优势(45%左右)和选择性(0.5左右)。木质素的相关谱带(1630,1510,1325 和 1265 cm-1)强度及半纤维素和纤维素的相关谱带强度(1740,1325,1160 和 898 cm-1)的变化也证实了这一结论。     

玉米秸秆木质素降解过程的CP/MAS 13CNMR和SEM表征

利用黄孢原毛平革菌对玉米秸秆木质素进行降解处理,通过CP/MAS 13 CNMR和SEM研究降解过程中木质素的结构变化。CP/MAS 13 CNMR结果表明:玉米秸秆木质素降解过程中,作为木质素结构单元主要连接方式的β-O-4键基本上没有被降解;木质素单位苯环的甲氧基含量稍有增加;S/G值降低,推断反应过程中紫丁香基优先参与反应。SEM结果表明:降解后的木质素空穴增多且增大、颗粒物质减少,主要是由于酶解木质素中大量碳水化合物的降解所致;比木质素更容易降解的纤维素和半纤维素也存在于样品中。CP/MAS 13 CNMR为木质纤维原料结构的定性和初步定量提供了可能,是传统定量表征手段的有力补充,具有一定的研究意义。     

不同云芝菌株腐朽杨木过程的扫描电镜研究

本文应用扫描电镜观察研究了白腐菌云艺（Coriolusvericolor）三个菌株腐朽杨木的过程，对试材的显微形态变化以及各菌株的降解特性进行了详细描述和探讨．实验结果表明，三个菌株降解木材的性能和方式存在着差异。NFU008对木质素和纤维素均具有很强的降解能力，它在腐朽早期优先降解胞间层中的木质素并能使纤维解离，在腐朽后期，它对纤维素产生强烈降解。NFU006对木质素和纤维素的降解是同时进行的，但对纤维次生壁中木质素的降解率明显高于对纤维素的降解率。NFU019降解木质素的能力相对较弱，但对纤维素的降解能力却很强，早期它以降解出生壁的木质素为主，而在腐朽后期它对纤维素产生剧烈降解。三个菌株最终均造成纤维细胞壁不同程度的减薄和破坏。     

仿生酶菌协同体系预处理木质素机理及特性

白蚁-真菌自然共生体系可有效转化木质纤维素类生物质,其本质在于对木质素物理结构的破坏和官能团的修饰,减少木质素对酶的非生产性吸附,从而提升酶解糖化效率,为生物质高效能源化利用提供新思路。本文基于白蚁肠道中存在的分解木质素酚类单元的漆酶（La）和蚁巢内降解木质纤维素的蚁巢伞菌（Te）,构建La和Te协同预处理木质素体系,比较La和典型的木质素降解菌黄孢原毛平革菌（PC）对木质素模型化合物碱木素的预处理特性。结果表明,在降解La预处理的碱木素过程中,Te产生的漆酶（La）和木质素过氧化物酶（LiP）活性最大值较未处理的碱木素样品分别提升43.3%、58.5%,PC产生的漆酶（La）和锰过氧化物酶（MnP）活性最大值较未处理的碱木素样品分别提升35.9%、31.6%。漆酶预处理强化了Te、PC对碱木素官能团的修饰和物理结构的破坏。傅里叶红外转换光谱分析（FTIR）表明酶菌协同体系处理后碱木素特征官能团的吸收峰显著降低。扫描电镜（SEM）和压汞测试结果表明酶菌协同体系对碱木素表面结构破坏严重,La和Te协同（La+Te）体系预处理后的碱木素平均孔径比单一La和单一Te分别显著提升31.1%、45.6%。经La+Te体系预处理后的碱木素最大酶吸附量较未处理的碱木素减少了51.5%,由于非生产性吸附显著减少,后续纤维素酶的转化率较未处理的碱木素样品提高了71.5%。本文证明了通过漆酶与真菌协同作用可有效改变碱木素物化特性,从而有效促进后续纤维素的酶解糖化,为木质纤维素类生物质高效利用提供指导。     

植物基因工程对生物燃料生物质特征的改进

全球每年有多达10～50Gt的廉价植物纤维素可再生利用。美国年产40亿加仑的乙醇,大多数是以玉米为原料生产的。目前多数利用微生物产生的纤维素酶对植物纤维素进行降解预处理,去除木质素,转化为可发酵的糖,进而生产乙醇。发酵前预处理及微生物反应器产酶成本都比较高。最新的植物基因工程研究致力于改善这种状况,降低成本,利用植物自身产纤维素酶和木质素酶来降解纤维素和木质素,或者提高生物质总产量或在植株中增产纤维素。     

木质素在离子液体中溶解及改性的研究进展

木质素是自然界中含量仅次于纤维素、唯一含有苯环结构的可再生生物质资源,对其进行有效的开发利用具有较高的经济价值和社会价值。离子液体作为一种新型绿色溶剂,在木质纤维素溶解方面展现了良好性能,本文粗略地概述了木质素的基本结构和性质,对木质素在离子液体中的溶解及改性等方面的研究进行了总结和综述,并在离子液体在木质素溶解降解方面应用研究的发展前景进行了分析讨论。     

木质素及其模化物催化加氢脱氧研究进展

木质纤维素类生物质是重要的可再生原料,可通过多种转化途径转化为燃料或精细化工品。木质素作为木质纤维素物质的重要成分之一,因其结构复杂,其利用一直没有得到很大突破。笔者以木质素及其模化物催化加氢脱氧制取化工品为着眼点,按催化剂种类综述了国内外木质素及其模化物催化加氢脱氧研究进展情况,并对其进行了分析评价,指出了木质素催化加氢脱氧的研究重点。     

氨化木质纤维的白腐菌降解

添加一定量的氨化麦草能促进白腐菌对木质纤维的分解作用,但如果氨化麦草的添加量超过20%,生长基质的重量损失又会下降,降解速率又会降低。比较添加氨化麦草和未添加氨化麦草生长基质经白腐菌降解后的纤维素含量,发现纤维素含量没有发生太大的变化。降解不同天数氨化木质纤维氮含量的变化显示,氮含量的降低率和木质素降解率的变化规律相一致,说明有机结合氮的释放和白腐菌对氮的吸收消耗与木质素的降解有一定的对应关系。     

Lignin Degradation by Flavodon flavus (Klotzsch.) Ryv. and Schizophyllum commune Fr. on Mangifera indica and Syzygium cumini Woods

Abstract

The lignin degradation by Flavodon flavus (Klotzsch) Ryv. and Schizophyllum commune Fr. on Mangifera indica and Syzygium cumini wood, changes in the chemical composition of the degraded wood, and production of extra-cellular lignocellulolytic enzymes were analyzed. White rot fungi F. flavus and S. commune selectively degraded the lignin of S. cumini rather than the holocellulose component, whereas simultaneous degradation of lignin occurred in the case of M. indica. After 90 days of pretreatment with F. flavus, total weight loss was 29% and loss in lignin content was 25.7% in M. indica wood. However, 8% loss of holocellulose was caused by S. commune in S. cumini wood. Extracellular enzymes from F. flavus such as ligninase and cellulase showed higher activity in degradation of M. indica wood than in S. cumini wood. Weight loss and changes in chemical composition of M. indica and S. cumini woods showed good correlation with enzyme activity in lignocellulose degradation. Woods of S. cumini showed resistance to the white rot fungi could be due to the presence of polyphenols.     

三种白腐菌对木质纤维素降解规律的初步研究

以接种量1%、接种龄7天为基准,在天然培养基及室温条件下,探讨了三种白腐菌对稻草秸秆中木质纤维素的降解动力学特性。结果表明,对木质素的降解速率桦褐孔(Inonotus sp)最高,红平菇(Pleurotus djamor)次之,白韧(Trametes sp)最低;对纤维素的降解速率与此正好相反。三菌株对木质纤维素的降解呈现一定的选择性,其中桦褐孔(Inonotus sp)对木质素的选择性降解优势最明显,选择系数达到2.99。     

应用黄孢原毛平革菌处理工业废水的研究进展

黄孢原毛平革菌能有效降解各种有机污染物，因此可用来净化工业废水。其降解主要依赖于它产生的胞外木素降解酶系，此酶系主要由木素过氧化物酶、锰过氧化物酶组成，本文介绍了黄孢原毛平革菌的降解机制和它在处理工业废水主要是造纸废水和印染废水方面的研究进展并对其应用前景进行了探讨。     

The Wood Preservative Potentials of Valonia,Chestnut, Tara and Sulphited Oak Tannins

This study investigated antifungal properties of four different tannins as potential environmentally friendly wood preservatives. Scots pine wood samples were impregnated with 3, 5, 10, and 15% valonia, chestnut, tara, and sulphited oak tannins, and then were exposed to brown rot fungi Coniophora puteana and Postia placenta, and white rot fungi Trametes versicolor and Pleurotus ostreatus attack to determine the best tannin type and the optimum concentration level for sufficient decay resistance. Leaching test was conducted in order to evaluate any loss in effectiveness in decay resistance due to possibility of tannin leaching. Tannins were found efficacious in suppressing brown rot fungi attacks when no leaching prior the decay test was used, however, they seemed to be ineffective against white rot fungi attacks. The lowest weight losses were obtained with valonia and chestnut tannins both for brown and white rot fungi probable related with their high ellagic tannin content.     

白腐真菌对染料的脱色降解及应用前景

通过对国内外文献的追踪,并结合实际研究结果,综合论述了白腐真菌对染料脱色降解的基本原 理、主要规律,以及各种染料和染料工业废水的生物降解性:总结展望了利用白腐真菌技术在染料工业废 水治理的实践中,所需解决的问题和应用的前景.     

白腐菌Cyathus stercoreus预处理芦苇制浆的研究

对用白腐菌Cyathus stercoreus预处理芦苇制取化学浆进行了研究。实验结果表明,用Cyathus stercoreus固体发酵处理后的芦苇所制烧碱—蒽醌浆的白度和粘度要低于未经发酵处理的对比浆的白度和粘度,而Kappa值高于对比浆;这个结果表明,白腐菌Cyathus stercoreus 对芦苇中的纤维素,半纤维素和木质素均有不同程度的降解能力,且对纤维素和半纤维素的降解要高于对木素的降解。且在白腐菌Cyathus stercoreus预处理过程中所分泌的各种木素降解酶的作用下,芦苇木素既发生降解,也发生一定程度的聚合。     

Correlation of 13C‐NMR analysis with fungal decay tests of polymeric structural wood constituents. I. Basidiomycetes

Heat treatment at relatively high temperatures (from 150 to 260°C) is an effective method to improve the durability of wood. This study investigates the reasons for the decay resistance of heat‐treated and nontreated wood with respect to the polymeric structural constituents by solid‐state cross‐polarization/magic‐angle spinning (CP–MAS) ¹³C‐NMR analysis before and after exposure to brown rot and white rot fungi. An industrial two‐stage heat‐treatment method under relatively mild conditions (<200°C) has been used to treat the samples. Brown rot fungi attack polymeric carbohydrates of nontreated Scots pine sapwood at C4, resulting in cleavage and eventually depolymerization of cellulose and hemicelluloses. The attack at the carbohydrate C6, which has never been observed before, is remarkable because the C6 ? CH₂OH group has no covalent structural function but acts in fixing the three‐dimensional carbohydrate configuration just by secondary forces. The ? CH₂OH group carries ? OH, which forms some of the strongest hydrogen bonds in the structure of the crystalline native cellulose. It is suggested that the fungus tries to cleave this group to open the cellulose crystalline structure into an amorphous structure to decrease its water repellency to facilitate enzymatic cellulose degradation. Considerable degradation of the hemicelluloses occurs during brown rot fungal exposure, whereas in general the attack on lignin is rather limited, being mainly demethoxylation. However, Gloeophyllum trabeum is an active brown rot fungus in the (partial) degradation of lignin because there is some indication of ring opening of the aromatic ring of lignin during fungal exposure. Aromatic ring opening has also been observed after exposure to Coriolus versicolor, a white rot fungus. The demethoxylation of lignin and some attack on wood carbohydrates are also characteristic of the attack of this white rot fungus. The CP–MAS ¹³C‐NMR spectra of heat‐treated Norway spruce reveal similarities but also clear differences after fungal exposure in comparison with nontreated Scots pine sapwood. Brown rot fungi seem to have a preference to attack the carbohydrates of heat‐treated wood at C4 and especially C1, cleaving the skeleton of cellulose and glucomannans. In untreated Scots pine sapwood, this attack mainly occurs at C4, the nonreducing end of the glucose unit. An attack on the out‐of‐the‐ring alcoholic group ? CH₂OH of the carbohydrates of heat‐treated Norway spruce is less obvious than that in untreated Scots pine. The attack on C3/C5 of the carbohydrates is remarkable, indicating ring opening of the glucose units, which has not been observed in nontreated Scots pine sapwood. Lignin degradation is limited to demethoxylation, and low or no aromatic ring opening is observed, even after C. versicolor exposure. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2639–2649, 2006